Matt, you estimated the RH to be maybe 25 or 30% at 20°C. It's often way higher than that in England throughout the year. I'm in my kitchen at 3 pm on a late November afternoon, and it's a comfortable 19°C (about 68° in your outdated Fahrenheit units) and the RH in here is around 65%, with that humidity dropping noticeably if nobody is in the room. That's pretty normal for us in Winter. The outdoor temperature is 6°C (43°F) at 80% RH, but it was close to 100% a few hours ago. In Summer, we might see typical outdoor temperatures of 20° / 71°F with RH of between 25% and 100% depending upon the weather.
I have said for years now roof foam will cause long-term damage. When you are trapping moisture between the O.S.B. and the foam. Roofers are also seeing asfault shingles fale with roof foam. If you have a leak the foam is a NIGHTMARE!!
Good job calling out how poor or misguided workmanship and lack of understanding of the building science leads to poor outcomes. I'm glad you're doing this work to help builders make fewer mistakes, less waste and better performing homes.
Unfortunately, especially in spec houses there is quite a bit of poor and/or misguided workmanship. The risk is that a significant number of bad spray foam installs (particularly in climates that are very cold or very humid) will give the rest a poor reputation and cause increasing difficulty in getting insurance or mortgages. In practical terms the perception can be as much of a problem as the reality.
@@benz-share9058I want to reiterate this. For all this to work four contractors need to know what they are doing with spray foam. Being on job sites where the trades are out back smoking pot and basically putting the minimum effort into their work, where the subcontractor himself only shows up every other day to inspect his workman’s work . . . .this in Houston aint gonna work out well. We have far less sophisticated systems that essentially. The framing contractors, the decking contractor, the foam applicator, the attic ventilation system, the roof deck and roofer. Matt even made a video on how this foam collects moisture at the peak, you got to know what you are doing to prevent it.
I'v been seeing this sort of nonsense since I used to read my dad's builder's magazines in the 1960s. Maybe I'm being a hard a* but the moisture issue seems pretty obvious. You don't use open cell foam anywhere near water- unless you're washing dishes with it. Who are the engineers who signed off on this? They should all lose their licenses. The companies, especially the principals of those companies should be paying to remove this stuff. A large French boat builder known for cutting corners on structure (weak thin plywood bulkheads, also absorbent), uses open cell foam for deck structure, gluing the frames onto hulls. (Would you glue or bolt a house to the floor deck? ) The decks after several years rot and fall apart. My boat has a closed cell foam core for the deck. It's effectively permanent. meaning my boat will last 100 years at least.
Where do you find a company to do the job right they all cut corners and they use this crap because it is cheap. They never should have licensed this cheap crap in the first place.
English carpenter and gc, now living in VT, USA. Spary foam was and often still is sprayed directly to the underside of roofs in older houses which are more often than not tiled in slate. The foam is sprayed to the back side of the slate. condensate forms on the rear of the slste, and air flow is now restricted meaning the moisture has no where to go and so rots the timber frame roof, that supports the slate. Meaning a whole new roof needs to be cut, then slated to remediate the problem.
I live in Ukraine, our codes prohibit to use flammable insulation in combination with wooden frames. It is also important to notice that ANY insulation material can damage wooden beams and frames of the root if you will block ventilation.
@avishnevsky7394 interesting, it's fascinating to hear perspectives from different global regions. From what I understand there is fire retardant foam and spray applications that fire proof the foam.
@@guyver9948 any modern foal-like material produces toxic fumes (PUR, for example). If you have flammable wall or roof (timber frames or beams), use wool. If you want to insulate floor (concrete-insulation-concrete) or make flat concrete roof - just use flammable XPS or EPS (twice cheaper, in some cases good alternative to XPS). If you have concrete, bricks, aerated concrete walls - there are some limitations, but in general it is allowed to use EPS (flammable and toxic fumes). Brick - insulation - plaster. Basalt wool around windows and doors, rest can be EPS.
I'm in Scotland, which is part of the UK, and we've recently put Kingspan between our rafters with an air gap so moisture can escape and not rot the wood. The issue is really as your second point - older houses here have no vapour barrier in the roof so small amounts of moisture do make it through. Spray foam here was frequently put in by dodgy firms looking to make a quick buck, and they would just fill the space in the rafters, which will trap moisture as the cold air hits the warmer air of the foam and condensates, rotting the roof at the condensation line.
He thinks he has to mind US Scotland is Part of the UK Thinking Americans Don't Know Geography... Hey, Bra, Americans fully known Scotland is Part of the UK, and of Course this Red, White, and Blue Bloodied American Ross knows Ross-shire was the Old Heart and Blood of the Highlands! But do you know the 1st Official Ross a name once Protected by Law Across the Empire, the Chief of the Great Clan Ross the 4th Earl of Ross Hugh Ross signed the Declaration of Arbroath a Percussor to the Declaration of Independence, and his daughter became Queen Consort of Scotland to the 1st Stewart King, starting a War for the Next Generation for the affront to Ross that was and the affront to come from such. Hugh Ross is the Ancestor to the Majority of Ross' in the Western World, and it was Betsy Ross' Uncle in Law Col. George Ross who was last to Sign the Declaration of Independence by Date. I bet you don't even know the Last Sea, is the Ross Sea, and Yet You Doubt Americans Geography Skillz!
Matt, I have no idea how the implications of closed cell foam at the roofline has not been recognized. I have been a roofer for 9 years now, 5 of which specializing in repairs. The first time I preformed a repair involving closed cell foam at the roof line was in 2021 on a 10 bedroom Spanish-villa style home in Florida built in 2005 with a Ludowichi terra-cotta roofing tile. Closed cell foam was used at the roof line down encapsulating the 2x10 trusses and continuing down the exterior walls. I state all this because the use of the spray foam caused this homeowner nearly $100,000 in repairs. He had roof leaks in 2 locations on the home The first one was on a 2 story rotunda, the leak had persisted for for an unknown amount of years because the water was not allowed to pass through to the drywall alerting the homeowner. The water was essentially trapped between the roof above and the foam below, with nowhere to go but to rot out sheets of 3/4in decking and the proceeding 2x10 trusses. I was scooping handfuls of what used to be solid wood. It was literally foam holding up this portion of the roof The water intrusion traveled down the roofline and down 2 stories before it found an exit at the interior baseboard, it was catastrophic, and would have been far less damaging had the builder NOT used spray foam. Once it exited at the baseboard was the only alarm the homeowner had that there was some sort of leak. The second leak was on the other side of the home at a small cricket above a cantilevered kitchen breakfast nook. Same problem, the water had nowhere to go that would notify the homeowner, it rotted out down the walls and wicked back about 4 feet of this 10 foot cantilevered area. At that point we had to call in an engineer to assess how to rebuild this mans 2 million dollar home. Long story short, all roofs have their lifespan, but due to many factors like workmanship, material defects, storm damage, etc. Leaks do happen and if the water cannot pass to a visible area soon due to closed cell foam preventing it, then the damage becomes disastrous.
I don’t think he cares to hear your message. He’s locked into that stuff. Makes him a lot of money. Any real builder with good knowledge would never put that foam locking everything yen above the rafters. The roof will only work if it isn’t ventilated properly, otherwise it will overheat and/or rot
I was polite but critical on a recent video of erv’s but have slowly drifted over. To “answer” your criticism, yes, mat has made a choice but I don’t believe he’s unaware of the risks. He mentioned he might make another video at the end. He also warrantees his work, like most builders, but I believe he actually stands but it and did talk about a video where honoring his words nearly bankrupted him. Anywho, my point is while yes, I do agree with the old guard thoughts of “if its man made it won’t last” and “accessibility is the only reliability” sort of thoughts I believe Mat is moving in the right direction. Just like it took time for me to be loosely convinced on ervs I do believe that modern day structures can last 100+ years. He does have a “perfect roof” series which he talks about a wall lasting 500+ years. His heart is in the right place. THAT hill, is the hill I’ll die on.
@@chiefeagle5882 I live in the Philly area in a home that is 85 years old and had closed cell blown into my rafter bays 14 years ago. No subsequent issues, and even the fiberglass shingled roof (now 26+ years old) is still in very good condition, though starting to show the *usual* signs of age-related deterioration, but nothing worse. I think moisture related issues are reveal more of an issue with the applicator and the use of open cell foam, which I would never use anyway.
Imagine the cost when someone needs to remove all that spray foam. Its literally going to be gluing everything together and blocking any visibility to water damage starting in the wood.
Thanks for dialing down on this. Most people have no clue about 'dew point', or that these older homes there and here in the U.S. were built drafty in order to vent moisture. This was back in the day of cheap oil energy. Drafty leaky homes never had mold or mildew rot problems. Not until skip sheathing was covered with plywood, and insulation was added over time. Details are important and we all appreciate your attention to these details.
I cannot think that older properties were "designed" to leak, our house is 1889 and solid stone. It was just built as it was, I really cannot see that they went out of their way to make leak. It just does, sash windows etc.
@@billdoodson4232 They didn't. They simply did not care. Standards back then approached home construction differently, based on materials and methods. They just ended up being naturally leaky and it was much more rare for someone to complain about 'black mold'.
I have to chuckle. I'm in the US and I have a home. I do not have a super efficient house. I have a home. In the Spring and Autumn, my windows are open. Well, in the Spring, the wife fusses about pollen, so there is that. I LOVE natural air flowing through my house. I even have - gasp - a whole house fan. Cook something stinky? Give me 10 minutes and it's gone. This is all sacrilegious to the energy efficient zealots. I don't care. A couple of years ago, I put a screen porch on the back of my house. Now I can leave those double doors open while my front windows are open as the thunderstorm comes in... or a nice breeze. If it gets too cold in the house, I toss a blanket on the bed. Now mind you, I raised a huge number of children in my home, so energy efficiency really wasn't on my target list. I was just happy the plumbing worked. I'm in the process of repairing some flood damage and learning all about insulation. Good video.
I used to use a lot of spray foam. Then we did a reno on a house that had what should have been a pretty minor roof leak, but because the foam trapped the moisture between sheathing and the foam it turned into a catastrophic amount of damage. There are still situations where it is almost a must, but we use it sparingly.
This is the problem with closed cell insulation, you don't see a roof leak. So, open cell allows condensation to rot the roof, while closed cell allows a roof leak to accumulate moisture. Insulation above the roof helps keep the wood from being cold enough to condense. Open cell below it helps a roof leak to be visible instead of rotting the structure. There are roofers in the US who won't repair a roof with spray foam below the roof line.
What I like about your work and content, Matt is that you know code but you also have a very extensive knowledge of the science, which sometimes is ahead of code.
Hi from the UK, the UK gov has a history of 'insulation' programs that are used as ways to make jobs. A lot of people who dont have skills end up with low paid jobs insulating houses, there are good people doing it but there's also a bunch that pop up just to sock up the government money before the deadline ends. It always ends up with a lot of problems, it's a rush to get the grant money over a real care for the work.
We have the same situation here in the USA. The government has weatherization programs that are largely staffed by unskilled workers that are poorly trained and have no basic understanding of physics. These weatherization programs often lead to homes having mold, moisture and IAQ problems.
It’s also a UK class E combustible, (not great) Polyurethane spray foam is nasty noxious foams at higher temperatures. Anyone who installed as part of any insulation program, should be up for fraud and anyone who has this in are rented properties loft and not ripping it out should be up for corporate manslaughter if the property does a Grenfell.
America needs to establish serious trade schools that specialize only in residential home construction. Offer a graded certificate for proper completion of the required course load. Homes are too expensive to have knuckleheads being taught by other knuckleheads at homeowners expense. In my opinion knowledgeable craftsmen are in short supply.
Nah, architects and engineers should be liable for overseeing key details in builds and hold liabilities for them. Municipalities should also be on the hook for inspection failures. Bank should own the mortgages and not be able to bundle and resell them, and “as is” sales need to be forbidden by lenders/insurance companies.
You would think, right? Every restaurant has to have a certified Food Manager on site when the health inspector walks in. Every home build should have a certified builder on site supervising at all times. That could be your "lead" carpenter.
Open or closed is bad for roofs. Issue is that if the roof has a leak, its make be impossible or very difficult to locate it. Water will pool & rot the roof. Either batts or cut peices of rigid foam panels should be used instead. You can always remove them for inspector or roof repair. I suspect in the next 3 to 7 years there are going to be a lot of US homes that need roof replacement caused by spray foam.
@@chaunceyspencer great you want a prize with that? Sure you can find leaks, but likely after its been leaking some time, unless it a huge leak, & the spotted leak might be in a different location. That said, Insurance companies will probably drop homes with spray foam at some point. So good luck with that!
I'm from the UK and the house I'm in had this. The survey report was basically what you said, so nice analysis there. In the end I offered the seller £20k less because of this and I had all roof tiles replaces which was quite a big job.
Hi from UK. Really interested to see this video Matt. Our Health & Safety Executive (HSE) have just issued a report on spray foam (no idea why as there is no H&S implication). They say that the risk of rot varies according to roof construction, type of foam and and climate, but if done properly is not a problem. Open cell seems to be preferred here, theory is so that moisture from below can pass through newer style breathable membrane as opposed to traditional impervious bitumen underfelt plus double height roof battens to ventilate under the slate / tile.roof. The HSE also advise open cell. Nothing is said about thickness or whether rafters should be covered..Vapour barriers unclear. Its just a mess. I read that just one senior surveyor set this hare running, as he came across a couple of rotten roofs, and now everyone is running scared. The standard foam thickess used here is only about 4". There is a bad history of closed cell being applied directly onto the underside of tiled or slated old roofs to "hold it all together" to keep the roof going past its life. Thats not good. Cowboy operators bolstered by well-meaning government grants, have applied the wrong foam in the wrong sort of roof in the incorrect way, and badly. Building techniques in UK have been changing, warm roofs are now a thing but that is fairly new. The more common traditional cold roofs need lots of through ventilation, with only 300mm rockwool type insulation on the loft floor. Lots of strong anti-foam opinion over here!
That lines up with so many stories I have heard from England on buildings. The regulators are extremely slow to address new tech, and by the time they do there are huge issues. And very aggressive opinions on it. Like your comment on closed foam, it is great stuff if used correctly and not to cover up structural or other issues like you pointed out. So now closed has a bad rep because of it.
@@darkshardrex7589 UK doesn't do prescriptive design codes. It's very subjective with objectives you should produce. And as the Grenfell Tower Fire showed, there are a lot of people in the UK confidently doing design and construction very wrong. who are overseen by inspectors who apparently have no idea what they are doing and standards bodies in the pocket of manufacturers.
I think you missed the comment where she said that she had black mould prior to the install. That is very common here, and indicates that there was already a problem with condensation to start with. The high humidity here means that people don't really trust wood buildings. One of the issues was the way that the grants were structured - it encouraged companies to quickly do a lot of installations with minimal / no training of the staff, and no consequences if something went wrong. So it did not matter to them whether or not the roof rotted afterwards.
This is a good example of what I've noticed in the trades since the 80's. A new code, a new material, or new SOP is introduced into the industry and contractors try to incorporate it without understanding the full scope of how it effects the overall build. In our area in Southeast Missouri in the 80's the contractors were trying to figure out if they should use plastic sheeting behind the drywall because we are a "cold" climate, so if they were doing it in the North, maybe we should too?? Because we are actually a "Warm/moist" climate it became a problem, however, I know of buildings that were built as late as 2009 that have plastic behind the drywall as a vapor retarder. Understanding cause and effect is sometimes a slow progression. I've heard of crawl space capsulation projects where homeowners started getting headaches afterward, then after cutting out the vents and re-introducing fresh air into the crawl space the headaches went away....Most likely they did not have proper ventilation to bring fresh air into the house, once capsulated, stack effect slowed down or stopped bringing fresh air in thus causing an air quality issue. The point I'm getting to is summed up into a saying I heard from a site works guy , he said: "Change the dirt, change the water". When you add or change a system in an existing condition, you change how other systems work. Unless a holistic systems approach is applied and designed into the changes, most likely there will be a failure. Stick to existing SOP and materials of the era the building was built in, or completely change all the systems so they work together.... Sadly, when something fails and insurance companies start paying out large claims, they have enough power to motivate changes and vilify materials and SOP. They don't care if it's an application problem, they just want to stop the losses immediately. Education in all aspects of the industry is desperately needed!!
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Yeap. Total ignorance pervades society and most trades. There's like 5 people who know what they're doing.
I agree with you and like your comment. Question: Are you also a bit older? I only say that because I have been a building contractor for about four decades and have seen many products not hold out as represented. A popular product "PEX"warranties 25 years, copper 50 years. 25 years is not very long buried in a wall of your home.
Absolutely correct. I live in an 80+ year old home and have been able to renovate and repair much of it because it’s all accessible ( water damaged fiberglass insulation, insulation in the wrong places, leaking pipes, substandard electrical wiring, etc.). If any of this was inaccessible, we’d be looking at a demolition and rebuild. Radiant heating embedded in concrete? You are putting a lot of trust in something that will be a nightmare to fix if it fails.
@@fsoileau I respectfully disagree with your Plumbing analogy. We don’t know the lifespan of PEX yet. Just because the warranty is set for 25 years doesn’t mean it’s not good for longer. We’ve all seen copper lines that are well over 50 years and are perfectly fine.
I have seen copper lines that were installed touching a dissimilar metal and have corrosion to the point of failure. It comes down to how it is installed same as PEX
I work for a pest control company in Florida and we will not warranty a roof if it has spray foam. If termites get into the roof deck or trusses that are covered in spray foam their is no way to inspect it and know. And if you fumigate a house with spray foam their is a chance of gas being trapped in the foam. Not recommended anywhere drywood termites exist.
Matt, here along the Gulf Coast in the US, non-native Formosan Termites are causing a LOT of problems. And the closer to the water you live the worse it is. Recently, I wanted to upgrade the insulation in our attic from fiberglass bats to spray foam. But I quickly found out that our termite company (Terminix) would drop us (cancel the bond) if we installed spray foam - for fear of trapped moisture which would in turn attract termites. Called other pest control companies and they said the same thing. Talk to your builder buddies in Houston about this. It is a BIG deal along the coast as every single home on or near the water has had a Formosan termite infestation. The Formosan termite colonies are an order of magnitude larger than normal subterranean termites and so they eat a lot of wood in a short time.
I've never seen any insects in foam. I have seen it in every other type of bat insulation. They love to nest in that stuff and once it gets wet it never drys out.
The problem I have encountered repeatedly in the US is that finding a good installer is incredibly difficult. It’s hard to know if people are doing things correctly unless you yourself are an expert. Had a mini split install recently where contractor made a subtle mistake welding (edit: not welding, brazing) the line set and this caused thousands of dollars in damage to the cassettes. The install LOOKS great. Inspector didn’t think to ask about it. My concern is that mortgage brokers and insurance may lump everyone together and cause problems for modern homes no matter if Matt built it or not.
I just made a comment about the lumping together. Big companies seem to do this quicker. Might have to seek smaller insurance co's to get coverage. Good to still be able to get coverage but limiting options isn't great.
Let's be honest. In some areas of the construction industry in the US far more than half of the workers aren't even supposed to be in the country in the first place. Of course they're going to take any and every shortcut available to them. Most of them don't even get paid per hour but get paid for job so the goal would be to do whatever you're doing is fast as possible.
@JustNo8808 You know what, l can be honest too. I've worked with a bunch of these guys over the years - talking about construction workers you pick up at home depot or wherever for day labor - work by the hour, get paid in cash at day's end. I don't know that they were all undocumented but no surprise if they were. The point is, they frikkin work. I'm sure there's exceptions but the guys I've worked with were friendly, respectful, focused, followed instructions, asked when unsure, and strived to do the work as expected. We'd get their numbers and call them back whenever needed for more projects. They were cheaper and better than calling some established subcontracting company that might get to you the Tuesday after next and then be delayed, and when finally on site do things their way instead of how we wanted it done. Americans literally did this to themselves; I'll take hispanos all day long! (That doesn't mean I'm for illegal immigration; I'm not. I'm for LEGAL immigration and carefully vetting everyone allowed to immigrate. I'm looking forward to the incoming administration sorting out the mess of the outgoing admin)
Great video! Thank you for making sense of this otherwise click-bate headline. I'm glad people like you are willing to do the work of what the old media used to do.
Having lived in the UK for over a decade, coming from continental Northern Europe, the type and quality of construction in the UK is shocking. It’s not only the cold climate, it’s the year-round humidity, and that they absolutely weren’t building for it. Your comment that some house are “under-insulated” made me choke. There are buildings here as recent as 40 years old that have either 2-3 brick thick solid walls, or a 2 brick thick wall with a totally empty cavity in between. No underfloor insulation, no roof insulation, just the expectation of cheap natural gas for all eternity. To the point that the only way to adequately dry out your house is to have heating on 24/7. The spray foam roof insulation ‘scandal’ is the result of an endemic culture of short-sightedness coming home to roost, not only once (when originally built), but twice (when foam was installed). New requirements here finally got higher air tightness and requirements for mechanical ventilation (ERV/MVHR), but even then the homeowner rarely understands what it’s for, what it does or how it’s supposed to work… much less maintains it properly.
@@johnm7249 Yes, those are the predominant features of many UK houses! But we can build warm, dry homes that are ventilated adequately but are not draughty.
I lived in the pacific northwest, namely western Washington state, which has a very similar climate to the UK. I remember living in cheap apartments with electric baseboard heat and aluminum windows that conducted cold and damp. I also attended the old Union Trade School, presently run by Seattle Community College, for two years (1993 to 1995) for carpenty and fine furniture. We got to work on several remodels including two gut jobs down to the studs. I have also owned 3 houses in the area, including my first house which was built in 1928 and my last house which was built in 2008. Vapor barriers for the crawl space were taught while I was in school. We were trained to apply a vapor barrier between the exterior sheathing wall (normally plywood or OSB) and the exterior cladding. All the remodels I worked on used paper-backed fiberglass that had an edge to staple onto wall studs / roof rafters. Over the top of that we stapled a plastic vapor barrrier. They may not be the most attractive but double vinyl windows are excellent insulators and the vinyl prevents excess moisture and is easy to wipe down and clean. My last house had a gas heat pump for botth AC and heat. This was the cheapest form of heating and AC and very effective. The air inside can become almost too dry in the winter, however. This house, built in 2008, also had a number of evenly spaced roof vents and a whole-house exhaust system built in to pull in fresh air from outside. I think there were also attic fans, as well. This house was highly efficient and I never experienced any mold or damp issues.
Howdy from a Texan ex-roofer (with young knees LOL) that lives in France but previously all over Europe/ME. First problem is that Roofs are NOT built like in the USA ... where we install plywood/OSB over the trusses and then apply a tar paper layer before asphalt shingles. Here it is def "open air" with clay tiles resting on batons and nothing but the wild blue yonder between. Throw in high winds (especially in the Athens area of Greece where I even lost tiles in high winds) in rainy conditions and you've got a "colander" type roof; your reference to 1x4" might be typical in the UK but nowhere else. Also keep in mind the Trusses rest on cinderblock or concrete wall structures; in Israel, the roofs are solid concrete in some cases ... sort of required in a Country where EVERY house/apt must have a "Mamad" or bomb shelter of high KSI reinforced concrete and it ain't just "rain" coming down like now. On a side note, Hurricanes and Tornados don't really cause much damage and the USA should learn from this construction method ... not much more expensive for new builds but would require a re-train of our crews ... much different approach. Anyway, I'm with the Insurance Companies on this one ... if the roof isn't sealed, rain/dew will certainly shorten the life span of the trusses/timbers as the spray foam is on the wrong side of the equation (trapped) ... "black mold" is worldwide BTW. So on a retrofit, clay tiles need to be remove, plywood/OSB installed and tar paper laid before reinstall of baton/tiles. "Governments" ??? What are ya gonna do??? Same ones that allowed "Lead" to be added to our Gasoline back in the 1920's just to quieten down valve trains ... not well thought out. We'll see how Solar Panels fare. Cheers.
Very informative comment, thank you. I've seen a few videos in the past about concrete homes and wondered why they weren't more popular. Seems like they would do better in severe weather. I'm not a builder, just curious.
As I see it, the issue is ventilation. Provide adequate roof ventilation, and this should be a non issue. I don't think it has anything to do with using osb sheathing. And almost nobody is using "tar paper" anymore... nobody who builds quality anyway.
@@TimTimTomTomI just took the tar paper off my 100 year old house and it was in great shape. Replaced it with more tar paper. I'm not convinced tar paper isn't quality. 🤷🏻♀️
@@TimTimTomTom ... and you live where? Want to nit pick over tar paper vs plastic wrap or plywood over GP water resistant sheathing ... everybody's got their opinion. But my point was neither is used traditionally in the UK or EU ... and when the wind/rain is coming at the roof horizontally, all that water will be trapped in the foam barrier instead and initiate rot; the reason for the content creator's post.
Let's be clear about "tar paper". I am 70, worked in construction before retiring. I have seen very few houses with actual "tar paper", and those were old houses. Newer construction ( most of my lifetime) uses "felt", which a lot of people confuse with tar paper. I had my own roof replaced in 2014 and they stripped and reinstalled 30 lb. felt, before laying the fiberglass shingles. Not putting the felt is kind of foolish in my mind as it insulates ( however slightly ) and provides additional barrier to water penetration should any get through the roofing.
Here in Norway we basically don't use any spray foam. It's seens as toxic, worse when it comes to fire and higher risk for water damage. I think all of the Scandinavia is the same
Here in Finland I use cellulose insulation in the roof of my log house, and no vapor barrier - only a permeable air barrier. No issues with moisture build-up and easy to check for potential problems.
Matt, most of the pre 1920 properties in England are slate or clay tile fixed on timber (lumber) battens fixed directly to the top of the rafters with no underlay, roofs then started to include a layer of roofing felt below the battens with this becoming the norm from about 1950. The use of timber sarking boarding above the rafters was generally only used on higher quality/status buildings, it has only become more common on domestic building recently, especially where there is habitable accommodation within the roof space. Spray foam only really began to be used in England from the 1980's and then generally only for retro fitting, its use mushroomed about 20 years ago when there were government grants available for installing insulation to older properties, this attracted many unscrupulous installers with little building science knowledge to promote it for totally inappropriate situations who then often had very poor inhalation procedures.
I love how Matt mentioned " home building scientists". Matt, we will look back at this foam craze and truly shake our heads. I have been against foam in any form(open or closed) since it was introduced. If you ever have to dig into it, it's a disaster. If you don't install it properly, off gassing. Leaks happen and closed cell will hide issues until it's too late. Let's be real, a lot of issues are from install error. 90% of installers will make an error. It's just not worth the risk. Just like the Govt in the UK pushed it and now are backtracking, it will happen here in the states. You can be a scientist in home building, BUT, my man, I have common sense and 25 plus years of working in every type of build up and down the east coast. I've never seen a build, regardless of price and said, this is perfection. It does not exist in 99% of the home builds. Unless its you or a this old house budget. That's not the norm, it's the exception. The codes need to chill out or our housing crisis will compound and get exponentially worse. The r requirements are getting out of hand. Your videos with stacks of insulation on the outside and inside are RIPE for major issues for homeowners down the road. Too many layers to hide disaster.
Exactly! I would rather have many good failsafe options instead of a single theoretically perfect ultimate. Instead of thinking like a wise military mission planner and having answers in advance for likely errors in execution these foam projects have almost no tolerance for errors. I don’t know how Matt sleeps.
While properly installed closed cell insulation with no leaks will solve the problems from vapor condensation, It can greatly increase the risks from bulk water from above when the roof fails. Yes, some people replace the roof when a periodic roof inspection indicates that the roof is close to end of life, many people first thought of roof replacement is when the brown stain in the ceiling gets larger and may take a year or more to figure out how to pay for it when they get an estimate of the cost. By that time, it won't just need a few pieces of roof sheathing replaced, it will need much more sheathing which is still glued to the insulation where it hasn't rotted to mulch and roof rafters with it. Won't it be fun to rebuild those trusses. Much of this damage will be done before any water gets through the closed cell foam to leave the brown stain on the ceiling.
The Perkin Brothers had a similar issue with the insulated foam forms used for concrete walls and basements. The termite guys would not warranty it so the bank would not finance it. So they did a video about it to warn other people about the potential problems they could face if selling or refinancing the house.
I've seen someone do a fire test on that spray foam and I've gotta say that in a fire it actually boosts the flammability of the house. See the heat melts it and it just turns into oil which burns hot and helps keep the fire going and spread.
There was also an episode of Holmes on Homes, or another Mike Holmes show I believe where they removed everything due to the spray foam installer spraying the foam too thick up in the attic, thus it would never fully cure and was slowly constantly outgassing, which was making everyone in the home sick.
@@stephenmitchell4393Technically correct, but could be misunderstood. So people understand - this has nothing to do with how many inches are applied in total. The problem arises when the applicator moves too slowly or over the same spot too many times before the foam can cure. Uncured product can get trapped behind cured foam and stay that way. It usually smells horrible, and therefore isn’t a danger because it’s caught.
@@nunyabidness3075 Right, as there is a difference between spraying 1 thick application, or spraying multiple thinner applications to create the same thickness.
Mr. Risinger, thank you so much for sharing this informative video! I have lived in northern Florida in a century-plus-some home for the last quarter century. As both the house and I have aged and the winters have gotten harder on us, I have frequently wished to insulate the uninsulated house a bit better. However, throughout my life, I had noticed that older houses without insulation and with well vented attics and metal roofs seemed to last forever, while newer houses with well-sealed roofs of any sort seemed to develop issues in only a decade or two. I thought condensation might have something to do with it, but I could not figure out why it was so much more harmful one way than the other... nor could I figure out how to insulate my attic without damaging what has been working for a hundred years, albeit in a chilly manner. You helped me immensely to understand which pitfalls to avoid, and how I might safely proceed, rafter-wise, by explaining the thermodynamics involved so clearly, by including great video examples, and by providing all of the relevant related specs and information about various materials at the same time. So, much gratitude from Florida, indeed! (Now, I just have to figure out what to do about the floor... Is it better to dig out and replace the unvented underpinning all around the crawlspace that stagnates the air beneath the house, and then replace it with breathable underpinning to let the air flow underneath.... to perhaps help inhibit the mold that seems to come up from below, underneath the sections of old linoleum? Is that moisture maybe from the higher water table beneath our Florida yards these days? Or would it be better to install a vapor barrier between the ground and the joists, and keep the underpinning intact to seal out the fresh air? Perhaps you already have a video for that too... I must go check!)
As a UK PassivHaus architect and project manager, I applaud your channel. I have been advocating that we need to build more like Americans here and move rapidly away from the so called traditional methods favoured by UK contractors.
I would strongly disagree with you, from experience of being from the UK and having family in the USA we should not be copying them. We have historical and economic reasons not to build in timber as the supply is not local and costly in comparison to the USA. Matt also references Dr Joe Lstiburek constantly, and rightly so. If you watch his lectures on the perfect wall or the institutional wall which will last and provide good performance for centuries then he basically describes the UKs standard brick and block cavity wall used in most houses today. Architecture jumping on the latest fad, like timber frame construction also cause reactions in regulations like the new part O, or overheating. Ignoring the fact that it contradicts part k and m for window guarding, the elephant in the room is no consideration is given to thermal mass in any of the calculations required for building control. This is not the case in Germany for example and makes light frame construction look great on paper but it's an illusion. The USA are heavy users of aircon, but with thermal mass it just isn't required especially in the UK where problematic hotter weather only lasts for a few weeks at most. The Romans knew it, the Greeks did, they still use it in the middle East and some parts of Australia now. A couple of years ago with 34c outside my living room 1910 cavity wall direct lime plaster on engineering brick with 150mm natural yorkstone exterior with a 30mm cavity didn't rise above 22c as tracked by digital thermometer and humidity sensors. My mostly timber framed well insulated room in the roof however didn't drop below 30c My point is copying someone else's homework for English literature may not help you in a French class if you get my meaning. The UK and USA have different resources and climate conditions, resources and physics dictate what will work economically not fashion.
@@colinmendelowitz249 no brick has nothing to do with it. In fact a lot of the house builders are looking to go timber frame as that's cheaper! The performance though is inferior in most ways other than speed of build and possibly air tightness but that's debatable.
@@nathanlegge7090 Thermal mass is indeed a good thing, but it's also usually very high-carbon. There is a tension there. It can be offset by very long lifetimes. Passivehouse says nothing about timber vs brick vs concrete vs whatever - it's all about building physics that adds up. And it removes any issues with condensation in the wrong places, and makes very comfortable houses with tiny heating loads, that don't overheat. The art is building good houses without an epic up-front carbon cost. Less brick and concrete generally helps with that, but stone can be very low-carbon if it's not had to come too far.
Love you, Matt. Great video. UK =England, Wales, Scotland and Northern Ireland. Also, mold is really prevalent in most of the UK. You have to wipe your windows off once a week. Homes have “vent bricks” which is basically an open hole through the wall for ventilation. No forced air heating, only radiators. Many families dry clothes on the radiators. No where will you find under 45% humidity. 60-80 is more the norm inside homes. No one in the UK should be surprised by mold in their home.
You have missed the point why the mortgage companies are unwilling to lend on spray foam insulated houses, while doing a great job of explaining the science. The issue is that the roofs with spray foam are hard to inspect for issues (especially caused by damp) and together with a significant number of poor installations this has led mortgage lenders to refuse to deal with spray foam. The idea of mortgage lenders or insurance excluding certain categories because they are awkward to deal with is certainly something that happens in the US, too. It doesn’t have to be spray foam insulation.
The next problem is most of these houses have to pass a blower door test when they test for air tightness, the regulations are getting tighter. I’m seeing some builders not pass the DET(duct envelope tightness) test because they didn’t spray foam. If states want their houses to get tighter without spray foam….a lot of builders arnt going to get their certificate of occupancy. It’ll be the builder apocalypse
Properly installed closed-cell foam can be a real boost for increasing the durability, comfort, and energy efficiency of the housing stock. Eliminating that option by refusing to insure it, is a bad move _in the long run._ In the short run it makes sense from the insurers' point of view, for the reasons you stated. What needs to happen is that the UK government needs to have more demanding education and training for insulation contractors, so that they know the right way to do things. This applies to building inspectors as well. With the contractors properly trained and regulated, the building failures won't happen and the insurers will be able to take on an appropriate risk level.
@@MrDbraultwhat is their issue with PEX? the only issue with PEX is not installing the fittings correctly. Assuming the job was done right, it's good for a hundred years.
When I had a “tar and gravel” roof replaced, I had the roofers install a LARGE thermostatically/hygrostatically controlled fan installed. It comes on when attic temps are above 90’F and when relative humidity is about 90-95%. The fan runs a lot in summer from the heat, but occasionally in the winter when we have damp foggy weather outside with dropping temperatures.
A popular phrase I've heard: Seal tight Ventilate right Yep we seal these up so much that the fresh air that used to permeate the envelope needs to be introduced mechanically.
The general public don't understand how important it is, but professionals for the most part do. Build tight ventilate right is a good catch phrase but you have to know the likely failure modes and mitigate them. Older designs have had hundreds of years of evolution to be perfected with local adaptations used for local climates. Foam insulation, chipboard, osb and to a lesser extent plastics are getting that evolution now and it's proving some to be not up to the task or causing secondary issues. Construction is quite conservative in it's approach for good reasons as the consequence of failure can be very expensive
Here in South Australia we have an airtight envelope, as its so dry [8" per year], but still got a vented roof space, above the envelope with height of 7'. Self Designed house. LOTS of research first.
Great treatment on this topic... I'm originally from USA and have been living in UK for 11 years... it's horrific here in terms of damp and mold problems. The average humidity level in most homes in UK is above 60% for example, which drastically alters that dew point you spoke of so it happens much more easily. Further, even in homes using ceiling level insulation and no under roof insulation as should be done here, many of them do not have proper venting of the attic space, it's all closed in. I guess it is to be expected, the UK gov was until some point in 90's telling their citizens to vent their clothes dryers into their homes to help heat the home! After decades of doing that they then discovered the massive mold and associated health problems it was causing and stopped recommending people do that, which then became a recommendation to use condensing dryers. These are better, they do still provide a small heat boost, but they also still do put some additional humidity in the home... how much depends on the dryer and if it's condenser is being maintained properly.
I live in the UK and never heard that the government advised to vent dryers into homes. All the advice I saw was to run a vent duct outside except for condensing dryers which are relatively OK to vent into the room - but only just. The real problem in the UK is that many homes have the kettle running almost 24/7 boiling water for the copious cups of tea consumed 🤣🤣🤣🤣🤣🤣🤣🤣
I'll venture a guess that no dedicated vents were needed when the tiles were just laid on battens, but with more felt and other barriers, the codes for venting didn't keep up with the changes. Here in the USA, vented roofs have a generous soffit openings, but with vinyl siding and foam sheathing popular in colder areas, that makes it very easy for a fire to migrate from a window to the attic, destroying a house in 10 minutes.
Hi Matt, UK roofs typically for the age you are talking about and even modern builds are felt underlayment, battens and terracotta tiles, plywood sheeting is not normally used. The loft spaces are built as cold roof, modern (last 30 years) will have ridge and soffit vents.
Thanks for the video! I’m a huge fan of closed cell foam. Have used it in a couple personal houses I’ve built and lives in within the last 20 years. Great stuff! I will mention based on my research I did on spray foam 20 years ago talking to the spray foam engineers in TX, they said the north in colder climates is where foam was first adopted, so I don’t see that being the issue. I agree with you, as I know for a fact, when the foam doesn’t adhere to the side of the rafter you get condensation. That’s why my foam guy used caulking to seal the edges of closed cell foam to the rafters where small gaps were at.
That house looks more like 90-100 years old rather than 40. Roof structures in UK are generally very different to US. "Under insulated" is an understatement. Recommended ceiling insulation in UK is 300mm (12"). Normal is fibreglass. Tiled rooves on tar paper with battens is normal and as you say relatively breathable. Your homes in the US are very different.
Hi Matt, as a carpenter in the UK we dont usually sheath the outside of our roofs like you guys over there. We have our roof structure which we then cover with breathable membrane and then batten and tile with slate or concrete tiles. A lot of the time when this type of insulation was used it was sprayed straight onto the old style bitumen roofing felt which also isnt breathable. There is also a lack of knowledge within the UK trades with reference to insulation and air tightness. Unless we are doing passive house stuff there isnt really much accountability. We need much more of a investment in the trades to bring in the knowledge of building science
Cheers from Canada. Been a guy who has built 2 - R2000 homes - 20yrs before they were adopted. Working on a NET ZERO. heavy insulation wall and ceiling, Double 1980 standards. It was a response by NBPOWER executives to the 73 OPEC crisis . Our area - is - 50 F. We need to release water - and decrease moisture into the house. For years - I have used - forced air movement. Thank you MATT - cheers!
Lived in England for four years, and owned a house for three. Our house was built, I believe, in the 50s or 60s. There are a number of paradigm changes with British homes. For the most part they weren't insulated at all. There was also no such thing as central heating. There was a coal fired fireplace in the sitting (living) room, and the door was left closed in the winter, so that was the only heated room in the house. That worked for them because it didn't get all that cold there. Being spoiled Americans, we wanted it warmer. There was cellulose insulation in our attic, but I don't know if it was there originally. We paid to have foam insulation blown into the cavity between our outer wall layers. They didn't use wood in the walls, so this wasn't a rot producing problem. We also had double glazed windows installed. It wasn't as warm as an American house, but it was far more comfortble. They didn't have pressurized hot water either, so you couldn't get warm water from a single tap. You had two separate hot and cold taps, or a 'mixer' faucet that was just two water lines close together in one fixture. It never truly mixed though.
@12:30 Matt is exactly on point here. My 100yo house near Boston was built EXACTLY as he describes it. Rafters, then 1x, then tar paper (cracked) then slate tiles. Yes it's slightly leaky. There is no way in hell I would ever do what my neighbors did and foam up the rafters (with closed cell). That's a disaster waiting to happen. According to several prominent building scientists, you're better off leaving it that way OR install baffles and then foam. Best is to replace the roof and install proper WRB. So I would say YES this problem is coming to America, in some places, mostly in the North-East and in particular New England (ironically).
I live in South Florida and I have had to do WDO inspections for home refinance. There has been issues with homeowners Who have put in spray foam insulation and cannot get bank approval. For the most common reason of it, making it inaccessible to see if there is or was termite damage that's being hidden/ iconcealed by the insulation. It also prevent us from being able to treat the exposed wood throughout the attic in a preventive fashion against wood destroying organisms using profucts like bora-care or premise2.
Good job. You may also want to look at the HSE (Health and Safety Executive) document referenced in one of the articles titled Spray foam insulation applied to timber sloped roofs in dwellings Modelling of moisture risk for retrofitted spray foam insulation in existing dwellings. They did the computer modeling and determined the risk.
The roof you have described, with some tar, is exactly what I have in the UK. The main problem I see is that the internal spaces humidity isn't 30% in the uk in most homes. More like 60% in many older homes. So the dew point is really low.
I believe you were underestimating the average relative humidity in the UK. In addition to that due to the high relative humidity outside, there’s going to be a certain amount of water vapor that penetrates the roof and is then trapped between the foam and the roofing material. When the temperature drops there’s not time for the moisture. to escape, and consequently will condense.
Canadian Home Inspector, Canada, good to see your video, thank you. Open cell foam must have a proper plastic vapour barrier, open cell is not used often here. Also I am aware of anyone insulating thier roof interior unless the room has a candretha ceiling. our insulation standard is R60 or 17" of blown in insulation, this is laid on top of the ceiling. I fthe home uses spray foam then it must be closed cell.
We always depressurize the building with a blower door and do a thermal imaging QA review of the foam in the roofline. Every imperfection we find the insulator marks with paint for touch up/correction. We find imperfections on 100% of the jobs as it comes with anything that is manufactured in mid air and at high speed :-). We believe this QA process is critical to the long term integrity of the roof deck.
Good video, the conclusions are good. You are low balling the humidity in the UK. Depending on time of year and location it can vary between 50% to 90%. Most roof construction is roofing felt on top of the rafters you see in the videos with batten nailed on top of that to hang the tiles from (tiles are nailed as required by building regulations) so not a lot between the cold tile and the inside of the roof space, nothing you would recognise as a deck. The big problem with this sort of work is the government grants for it. Companies will convince people that the the new (funded) thing is good for them and do the work, then get paid by the government irrespective of whether or not the house is suitable for the work or not. This behaviour repeats with each new government initiative to improve the (elderly) housing stock of the country.
FYI, the UK is relatively humid. Expect roughly 60% humidity indoors even with some use of a dehumidifier, and 80-95% humidity in an uninsulated loft. Even without spray foam involved, it's very common to have condensation issues if additional ceiling level insulation is added, cooling the loft. Middle-aged housing stock (say 1970s) has non-breathable bituminous sarking felt under the tiles and typically relies on gaps at the eaves for air-flow - which may be blocked by extra insulation or boarding laid down for storage. Without adding felt lap vents or ridge vents, it'll be raining inside just from warm moist air leaking into the loft and condensing. Makes it easy to see why spray foam would be an issue. You're still getting warm moist air escaping into the loft, but now it's condensing right at the rafters with no ventilation to dry it out, migrating through the foam as you say. And if you encapsulate the rafters, no-one can inspect to see if any water is getting through the tiles - so neither open-cell nor closed-cell foam is really acceptable for a retrofit.
I agree with the humidity, as a Brit who moved to Massachusetts it is incomparable. 60-70% compared to 30-35%. Also the weather, it pretty much rains or is damp every day in the UK from November to March. In Massachusetts in December to February it is super cold but dry. Another thing is Brits tend to air dry their clothes in their house, Americans just use a dryer as electricity is so cheap, like 1/2 the price.
Yes or more in the attic. But also the ventilation at the rafters is missing in many of these situations, so there is often no path for the moisture to be removed.
In Houston, we have seen insulation companies add foam insulation to roofs in older existing homes, causing a lot of trouble. Excess humidity is due to their existing A/C system now being oversized, and the gas furnace is not operating correctly because they seal the attic.
I kinda have this debate often with people online. Spray foam is fine but you need to do a bunch of work first to make it acceptable, it’s best on new construction.
I would argue it's not fine at all since it traps every service in a permanent layer of crap which can't be recycled, reused, easily removed (if later renovations etc). The side of every leading spray foam bottle says "contains carcinogens", so I doubt spraying your home in the stuff is good for you. Also only works with houses continously covered in OSB or plywood.
Matt, thanks for the video. The 2024 International Residential Code, and its predecessors, deals exactly with this issue in Section R806.5-UNVENTED ATTIC AND UNVENTED ENCLOSED RAFTER ASSEMBLIES depending on climate zone. The issue that is being overlooked a lot of times is the air-permeability of spray foam. The IRC defines "air-impermeable" (for the purpose of moisture management) as "an insulation having an air permeance equal to or less than 0.02L/s-m^2 at 75Pa pressure differential as tested in accordance with ASTM E283 or E2178." Air-impermeabilty is used by the IRC in insulation to prevent condensation on condensing surfaces as described in the video. There are open-cell foams that are air-impermeable and closed cell foams that are air-permeable. Some open cell foams are air-permeable until they are applied to a certain depth and then they become air-impermeable. The details of each foam products performance must be observed and you have to dig a bit to find it. The details are in third-party evaluation reports published by multiple agencies, the ICC-ES (International Code Council Evaluation Service) as ESR reports (google your favorite foam), Intertek CCCR-Code Compliance Research Reports or UL ER- Evaluation Reports., etc. In my office we do not use the term OPEN CELL or CLOSED CELL as it does not accurately reflect the air permeability. The key for the consumer is to KNOW what is being installed.
@rsmith02 The extention the house, block all the ventilation, build a roof over a roof... a total of seven layers of shingles on over the others on a 2/12 pitch... And they use spray foam to hides everything
I’m an engineer and I HATE the idea of spray foam insulation for entire houses. It is super hard to put fires out, it can mold easily, it constantly off gasses which reduces overtime, but is still there. Not in my house. Only as gap sealer
I wouldn’t have thought that the humidity in a typical UK home would be anywhere near 35%. Do most UK homes use forced air heating that would lower humidity. The weather in the UK is typically humid and the weather is typically rainy almost like Seattle.
Closed cell for my entire envelope. Circa 2007, new build, unvented roof. Home builder for 25 years.mid Atlantic. I've cut into sections for additions. 0 problems. As with anything, installation by competent professionals with proper conditions is key.
I put a layer of ridged foam between the decking and spray foam. If the decking needs replaced we should be able to peal the bad decking off without touching the spray foam. Time will tell though
It can be moist but it must then dry completely because mold grows in consistently moist areas only. Excellent video presentation that really got me thinking.
Another comment regarding moisture control: It’s my position that you will never be able to completely keep moisture out. Even if you did, I’m convinced the seal would fail over time. A “tight” house is a trap for moisture. Instead, I focus on what I call “moisture management.” I assume moisture will get in - so I make sure there’s a Way for the moisture to get out. For example, I advocate installing siding with a small gap between the siding and the moisture barrier. That way, any moisture that gets in can drain out. I ensure there’s a clear air path on the underside of the roof, from attic vents to ridge vent.
Spray foam can definitely cause problems with trapped moisture ending up against the wood surfaces. The moisture can enter from above (roof leaks) or below (humidity enters and reaches dew point) as you pointed out. The interior moisture can penetrate into the wall or roof cavity from the interior, if the material's permeability is high enough, and then it is trapped inside with no place to go to dehydrate. Air sealing the exterior framing/ sheathing surfaces can cause similar issues by trapping moisture in the framing cavity. A moisture barrier ( low perm primer ) can help at the interior surface of the walls and ceiling. If the lowest permeability factor is at the interior surface, then the framing cavity can stay dryer, in theory.
Glad that the build show is addressing the diference between the UK and US on spray foam insulation. I live in London and most of our stock is Victorian then 1930 to 1970 stock. We have a very low new build rate. we had you black mould creases in the 1980 with dry rot in new build timber homes. This lead to a reduction in timber framing in the UK. Most new houses are block and brick cavity construction. on older properties, we did not have parking ( underlament to the US). As Matt points out we traditionally have on condition loft spaces.) No roof vents or poor loft ventilation. Moisture is Or was controlled by ventilation through the slate or tiled roofs. ( I am leaving out Thatched roof as that is outside of my practice area). So spraying foam between the rafter is not desirable. As it creates condensation. When roofs are recovered a marking is normally added. But is normally a bitumas membrane type. It not common to use a smart breathable membrane at this point. There is also a tendency to use the foam on roofs that have reached the end of there lifes. Which is not appropriate. Hence banks and insurers .
Good on you Matt for doing a deeper dive on the story. One of the ills that has grown out of the digital landscape is a tendency to take in a headline and little else. Throw in the obligatory shock factor built in to the headline to encourage clicks, and it makes the "drive-by takeaway" that much worse.
Chatgpt can be very accurate if you ask it questions the right way. The best way I have seen it explained is talk to it like you are walking up to a random person that knows everything to ask them a question. If you give some vague question it will get confused. If you give it a very detailed question it will be accurate. I also never do what is called zero shot prompting where I try to get an answer immediately. I'll tell it what I'm trying to accomplish and get it to first explain the process it should take to get an answer and I'll usually also give it a role to play. Once it gives me that information I'll tell it to start to work through the problem. Especially with the new models they have it will spend a lot of time working through the problem. The funniest thing I did was I figured out a bunch of different "experts" that would provide good input and once each of them gave me an answer I asked them to have a meeting. It took a while to get the answer but the output was funny because it literally was a meeting where they ended up having meeting minutes and I could see them actually debating each other and correcting any issues they had missed. The output was 61 pages long.
@hotshot619 Yes, thank you for saying something. It drives me crazy the way people have come to just reflexively trust the Elaborate Lie Machine. It's designed to spit out sequences of words based on probability--it's not an actual, thinking researcher that can understand what it's saying.
I agree in the sentence that cgdp is a bad source of info , better search for info and go to Links that is presented and sheck the quality of that info . Whether stats in the uk : go to there whether afforety.
I love that we are complaining about short form content not having all the details and then we use chat gpt as part of our research into the topic. The irony is clearly lost.
Most of the problems you described seem to be common practice once you get off the high-end of your foam insulation packages and go down to the cheap house builds and the people that do that they do all the bad things you're talking about. So I can definitely see these problems coming here to the US.
Sure, just ignore the squirrels running around and pooping everywhere, and ignore freezing your ass off in winter or paying $400/mo in summer to air condition the place. Ventilated attics are OUTDOOR SPACES.
@@Crusader1815if you do insulated rafters with narrow outdoor venitilated slits under the roof boards ( like 2") you can have full room height, and get a nice" non boxlike" room volume.
Before I watch the rest (I'm only 2 seconds into the interview), Im going to veture a guess that (like everything else HVAC related in GB) they are doing it wrong; Government subsidies caused a bunch of businesses to spring up overnight without proper understanding, training or expertise and a whole lot of salesmanship (backed by government messaging). Now back to it, let's t see how my prediction holds up.
I concur. We had our city mandate on homeowners to put water pressure regulator. They said that if we do it within two months, we can get reimbursement, but if we don't, later on we will have to foot the bill. They even gave us suggestions which companies to call. After install, it needed to be inspected by the city inspector. I called and guy was send to our house in 2 days. I checked during those days about total cost and the highest price for top tier back then was $95. City stated that they will reimburse up to $850. Notice word "up to". The guy came, did it in 15min and charged us .... yes you guessed it, $850. Then magically city Inspector for which the wait time is usually over a month, showed up 2 hrs after job was done. We both went into crawl space and thank God he came so fast (although I found out later that they scratching each other's backs). The water was dripping and since we always had bucket sitting under crawlspace water shut off valve, I had already about 1 /4 of gallon of water in a bucket. I panicked and told the Inspector that I will call the guy to get his butt back right away to fix the leaking issue and a da... Inspector tells me " don't bother him, it will be ok. In time the dirt and and grease from the surrounding area will plug up the connection and act as seal and stop the leak. I know that guy and he is always doing a great job". That's when my red flag went up. The city inspectors and other officials were directing people to their buddies because there was "free" money flying around. I told his that I don't give a crap since I paid $850 for job that took 15 min and part for $95 (they probably had further discount) and based on travel cost of the company and per Hr labor, should cost on high end even if charging 1 hr labor, no more than $550. I called the guy back. He came back ticked off. This time I watched him like a hawk and it took him less then 7 min to fix it and no leak after that. I was furious because this city reimbursement money didn't come off the tree, it came for property taxes from all of us. People who couldn't afford to pay upfront costs and be home magically waiting during the week day hour for installer, got screwed.
From the UK here, you are 100% correct. Companies springing up and taking the Government money and doing an awful job and the homeowners then have to live with the consequences. Same thing is happening here now with Heat Pumps. Company’s springing up, taking government money and doing terrible jobs leaving the homeowners living with something costing them 4x the running cost of the perfectly serviceable natural gas boiler they had ripped out in the name of being green!
@@gund89123 It does, but it's for insulation in the general sense, not specific to foam. Also, these are established industries in the states, with experience and established best practices. This is not to say that there are not shady installers making a mess of things in the states, there are, but it's not an entire sector that has just sprung up out of nowhere based on artificial incentives and promotional messaging (advertising) from government.
Great analysis, speaking from the UK. We have a history of government-incentivised unsuitable home improvement initiatives that later have to be undone. Also see cavity wall insulation and external wall insulation for examples.
Cavity wall insulation is 99% a good thing. There are a few examples of disasters, but millions of homes have been done with few problems. EWI is even more of a good thing because you have to really screw it up to cause problems. Mostly that comes from doing it on the cheap and using siliconed-on capping rather than extending rooflines, which of course practically guarantees a leak down the back eventually. You are quite right that some of the shoddiest schemes have been done under grant-funding, and we've had far too many badly-done stop-start grant schemes. That doesn't mean that govt money to improve the housing stock is a bad things, nor does it mean that cavity wall insulation and EWI are bad things. We actually need dramatically higher rates of retrofit for buildings, and the more of them that are EWI-based the better IMHO. It's usually the best technically and lowest-risk major insulation intervention. But like everything in building, the detailing and design have to be right.
I worked in a building supply center in the Canadian prairies (think very cold) in the late 70's. The government had a program of rebates for increasing the insulation in your home. In addition to the standard fiberglass and styrofoam insulation people were using blown in insulation. The blown fiberglass insulation in the attics to increase the R value worked decently well. However in the walls there were two other types of blown insulation. The first was urea formaldehyde foam insulation (UFI) which was later banned in Canada. The fumes would literally poison the home. The only solution was to tear the walls out and scrape the insulation out. Needless to say these houses couldn't sell or get mortgages. The second type was cellulose insulation which was basically very finely ground up newspaper or wood pulp treated with a fire retardant. It work quite well. However over time the fire retardant would leach out (although the manufacturers say they have improved the process). Currently one manufacturer says the life expectancy of the insulation is 20-30 years (compared to fibreglass at 80-100 years). Another type of insulation for attics was vermiculite (Zonelite). This was a natural product that was later found in many cases (but certainly not all) to be contaminated with asbestos. Not good. Do your research and remember that sometimes the latest and greatest innovation isn't always the best.
Insulation in the UK is generally very poor to non-existent in many houses, and I don't mean to stereotype, but most people's solution is to just put on a sweater and drink a hot cup of tea.
@@mattundercoat it is what i grew up with 😆the attic at my parents place had about 2 inches of glass wool insulation which was dong absolutely nothing. Quick trip to b&q and now they have 10 inches, and you could feel the difference immediately
I stopped watching Matt years ago when he said you want your house like a Yeti cooler. I cant even watch him now, I only came for the comments. My best guess is this dude will have a class action lawsuit by all the homeowners he's built for with his foam crap.
The predominant feature of UK climate (not that we have 'climate', we have weather) is the damp. Relatively high cold temperatures feel bitterly cold due to the humidity. We have a saying : too cold to snow. This comes from the times it gets really cold is when there aren't any clouds.
To quote Matt at 13:40 "...when an invariable leak possibly happens..." Exactly! Roofs WILL leak -- period! I've always felt that spray foam has no place in the rafters of a roof.
One huge error in your equation at around 8:00 is that the RH in the UK is way higher than you assumed. I just spent a year there and the average RH is around 60% there throughout the year (exterior during the winter is around 80% average, interior is in the 50-60% and yes they deal with tons of mold there), which makes the issue being talked about significantly worse.
Well said, Matt- glad you took the time and expanded the perspective. Short form vids have their downside for sure.
Thanks Brother. Hope you didn’t take this as me talking badly about you. Always appreciated your awesome content!
Yeah they have turned the world into spastic sheep.
Matt, you estimated the RH to be maybe 25 or 30% at 20°C. It's often way higher than that in England throughout the year. I'm in my kitchen at 3 pm on a late November afternoon, and it's a comfortable 19°C (about 68° in your outdated Fahrenheit units) and the RH in here is around 65%, with that humidity dropping noticeably if nobody is in the room. That's pretty normal for us in Winter. The outdoor temperature is 6°C (43°F) at 80% RH, but it was close to 100% a few hours ago. In Summer, we might see typical outdoor temperatures of 20° / 71°F with RH of between 25% and 100% depending upon the weather.
I have said for years now roof foam will cause long-term damage. When you are trapping moisture between the O.S.B. and the foam. Roofers are also seeing asfault shingles fale with roof foam. If you have a leak the foam is a NIGHTMARE!!
If the foam could be placed away (air gap) from the O.S.B. to allow circulation it would be much better.
Good job calling out how poor or misguided workmanship and lack of understanding of the building science leads to poor outcomes. I'm glad you're doing this work to help builders make fewer mistakes, less waste and better performing homes.
Unfortunately, especially in spec houses there is quite a bit of poor and/or misguided workmanship. The risk is that a significant number of bad spray foam installs (particularly in climates that are very cold or very humid) will give the rest a poor reputation and cause increasing difficulty in getting insurance or mortgages. In practical terms the perception can be as much of a problem as the reality.
@@benz-share9058I want to reiterate this. For all this to work four contractors need to know what they are doing with spray foam. Being on job sites where the trades are out back smoking pot and basically putting the minimum effort into their work, where the subcontractor himself only shows up every other day to inspect his workman’s work . . . .this in Houston aint gonna work out well. We have far less sophisticated systems that essentially.
The framing contractors, the decking contractor, the foam applicator, the attic ventilation system, the roof deck and roofer. Matt even made a video on how this foam collects moisture at the peak, you got to know what you are doing to prevent it.
If a mistake anywhere in the build can lead to massive issues, I’d think twice before installing. Good craftspeople can still make mistakes
I'v been seeing this sort of nonsense since I used to read my dad's builder's magazines in the 1960s. Maybe I'm being a hard a* but the moisture issue seems pretty obvious. You don't use open cell foam anywhere near water- unless you're washing dishes with it. Who are the engineers who signed off on this? They should all lose their licenses. The companies, especially the principals of those companies should be paying to remove this stuff.
A large French boat builder known for cutting corners on structure (weak thin plywood bulkheads, also absorbent), uses open cell foam for deck structure, gluing the frames onto hulls. (Would you glue or bolt a house to the floor deck? ) The decks after several years rot and fall apart. My boat has a closed cell foam core for the deck. It's effectively permanent. meaning my boat will last 100 years at least.
Where do you find a company to do the job right they all cut corners and they use this crap because it is cheap. They never should have licensed this cheap crap in the first place.
English carpenter and gc, now living in VT, USA.
Spary foam was and often still is sprayed directly to the underside of roofs in older houses which are more often than not tiled in slate.
The foam is sprayed to the back side of the slate.
condensate forms on the rear of the slste, and air flow is now restricted meaning the moisture has no where to go and so rots the timber frame roof, that supports the slate.
Meaning a whole new roof needs to be cut, then slated to remediate the problem.
lots of what im seeing for our area "VT" spray foam should be limited to below grade applications for existing builds.
I live in Ukraine, our codes prohibit to use flammable insulation in combination with wooden frames.
It is also important to notice that ANY insulation material can damage wooden beams and frames of the root if you will block ventilation.
In Scotland Slates are nailed onto sarking boards (using copper nails)
@avishnevsky7394 interesting, it's fascinating to hear perspectives from different global regions. From what I understand there is fire retardant foam and spray applications that fire proof the foam.
@@guyver9948 any modern foal-like material produces toxic fumes (PUR, for example). If you have flammable wall or roof (timber frames or beams), use wool.
If you want to insulate floor (concrete-insulation-concrete) or make flat concrete roof - just use flammable XPS or EPS (twice cheaper, in some cases good alternative to XPS).
If you have concrete, bricks, aerated concrete walls - there are some limitations, but in general it is allowed to use EPS (flammable and toxic fumes). Brick - insulation - plaster. Basalt wool around windows and doors, rest can be EPS.
I'm in Scotland, which is part of the UK, and we've recently put Kingspan between our rafters with an air gap so moisture can escape and not rot the wood. The issue is really as your second point - older houses here have no vapour barrier in the roof so small amounts of moisture do make it through. Spray foam here was frequently put in by dodgy firms looking to make a quick buck, and they would just fill the space in the rafters, which will trap moisture as the cold air hits the warmer air of the foam and condensates, rotting the roof at the condensation line.
What is Kingspan?
@@rsmith02 a fibre-free core rigid extruded polystyrene insulation
@@rsmith02pir insulation
He thinks he has to mind US Scotland is Part of the UK Thinking Americans Don't Know Geography... Hey, Bra, Americans fully known Scotland is Part of the UK, and of Course this Red, White, and Blue Bloodied American Ross knows Ross-shire was the Old Heart and Blood of the Highlands! But do you know the 1st Official Ross a name once Protected by Law Across the Empire, the Chief of the Great Clan Ross the 4th Earl of Ross Hugh Ross signed the Declaration of Arbroath a Percussor to the Declaration of Independence, and his daughter became Queen Consort of Scotland to the 1st Stewart King, starting a War for the Next Generation for the affront to Ross that was and the affront to come from such. Hugh Ross is the Ancestor to the Majority of Ross' in the Western World, and it was Betsy Ross' Uncle in Law Col. George Ross who was last to Sign the Declaration of Independence by Date. I bet you don't even know the Last Sea, is the Ross Sea, and Yet You Doubt Americans Geography Skillz!
I’m in Scotland too. Another problem is our roofs leak due to age. The roof will have little drying potential if you spray foam
Matt, I have no idea how the implications of closed cell foam at the roofline has not been recognized.
I have been a roofer for 9 years now, 5 of which specializing in repairs. The first time I preformed a repair involving closed cell foam at the roof line was in 2021 on a 10 bedroom Spanish-villa style home in Florida built in 2005 with a Ludowichi terra-cotta roofing tile. Closed cell foam was used at the roof line down encapsulating the 2x10 trusses and continuing down the exterior walls. I state all this because the use of the spray foam caused this homeowner nearly $100,000 in repairs.
He had roof leaks in 2 locations on the home
The first one was on a 2 story rotunda, the leak had persisted for for an unknown amount of years because the water was not allowed to pass through to the drywall alerting the homeowner. The water was essentially trapped between the roof above and the foam below, with nowhere to go but to rot out sheets of 3/4in decking and the proceeding 2x10 trusses. I was scooping handfuls of what used to be solid wood. It was literally foam holding up this portion of the roof The water intrusion traveled down the roofline and down 2 stories before it found an exit at the interior baseboard, it was catastrophic, and would have been far less damaging had the builder NOT used spray foam. Once it exited at the baseboard was the only alarm the homeowner had that there was some sort of leak.
The second leak was on the other side of the home at a small cricket above a cantilevered kitchen breakfast nook. Same problem, the water had nowhere to go that would notify the homeowner, it rotted out down the walls and wicked back about 4 feet of this 10 foot cantilevered area. At that point we had to call in an engineer to assess how to rebuild this mans 2 million dollar home.
Long story short, all roofs have their lifespan, but due to many factors like workmanship, material defects, storm damage, etc. Leaks do happen and if the water cannot pass to a visible area soon due to closed cell foam preventing it, then the damage becomes disastrous.
I don’t think he cares to hear your message. He’s locked into that stuff. Makes him a lot of money. Any real builder with good knowledge would never put that foam locking everything yen above the rafters. The roof will only work if it isn’t ventilated properly, otherwise it will overheat and/or rot
@@steveperreira5850 It's not real for Matt, it's for other people in the comment section. Make sense?
I was polite but critical on a recent video of erv’s but have slowly drifted over. To “answer” your criticism, yes, mat has made a choice but I don’t believe he’s unaware of the risks. He mentioned he might make another video at the end. He also warrantees his work, like most builders, but I believe he actually stands but it and did talk about a video where honoring his words nearly bankrupted him.
Anywho, my point is while yes, I do agree with the old guard thoughts of “if its man made it won’t last” and “accessibility is the only reliability” sort of thoughts I believe Mat is moving in the right direction. Just like it took time for me to be loosely convinced on ervs I do believe that modern day structures can last 100+ years. He does have a “perfect roof” series which he talks about a wall lasting 500+ years. His heart is in the right place. THAT hill, is the hill I’ll die on.
Sounds like they used open cell not closed cell. Open cell does not have stop vapor where closed does.
@@chiefeagle5882 I live in the Philly area in a home that is 85 years old and had closed cell blown into my rafter bays 14 years ago. No subsequent issues, and even the fiberglass shingled roof (now 26+ years old) is still in very good condition, though starting to show the *usual* signs of age-related deterioration, but nothing worse. I think moisture related issues are reveal more of an issue with the applicator and the use of open cell foam, which I would never use anyway.
I like rockwool. Spray foam makes a mess to go in and renovate modify years later, plus fireproofing is a giant difference between them
It's also vapor permeable so not appropriate for an unvented assembly in cool climates. Would make more sense with a ventliation channel at the top.
Imagine the cost when someone needs to remove all that spray foam. Its literally going to be gluing everything together and blocking any visibility to water damage starting in the wood.
And rockwool is great for growi g weed so... that's another +1 in my book
@@rsmith02 they call them a 'maximum' ventilation thing- as when someone call a tissue kleenex or a refrigerator frigidaire
@@b0rd3n???, do you mean the kelvinator?
Probably one of the best explanations I have ever heard on this topic.
Amazingly good job researching these details. Thank you for making this video!
Thanks for dialing down on this. Most people have no clue about 'dew point', or that these older homes there and here in the U.S. were built drafty in order to vent moisture. This was back in the day of cheap oil energy. Drafty leaky homes never had mold or mildew rot problems. Not until skip sheathing was covered with plywood, and insulation was added over time. Details are important and we all appreciate your attention to these details.
I cannot think that older properties were "designed" to leak, our house is 1889 and solid stone. It was just built as it was, I really cannot see that they went out of their way to make leak. It just does, sash windows etc.
@@billdoodson4232 They didn't. They simply did not care. Standards back then approached home construction differently, based on materials and methods. They just ended up being naturally leaky and it was much more rare for someone to complain about 'black mold'.
I have to chuckle. I'm in the US and I have a home. I do not have a super efficient house. I have a home. In the Spring and Autumn, my windows are open. Well, in the Spring, the wife fusses about pollen, so there is that. I LOVE natural air flowing through my house. I even have - gasp - a whole house fan. Cook something stinky? Give me 10 minutes and it's gone. This is all sacrilegious to the energy efficient zealots. I don't care.
A couple of years ago, I put a screen porch on the back of my house. Now I can leave those double doors open while my front windows are open as the thunderstorm comes in... or a nice breeze.
If it gets too cold in the house, I toss a blanket on the bed. Now mind you, I raised a huge number of children in my home, so energy efficiency really wasn't on my target list. I was just happy the plumbing worked.
I'm in the process of repairing some flood damage and learning all about insulation. Good video.
I used to use a lot of spray foam. Then we did a reno on a house that had what should have been a pretty minor roof leak, but because the foam trapped the moisture between sheathing and the foam it turned into a catastrophic amount of damage. There are still situations where it is almost a must, but we use it sparingly.
question: why don't they put a drainage plane like dimple mat from eves to ridge vent?
This is exactly why I don’t use spray foam. Roof leaks are inevitable, and if you can’t see them you get a catastrophic mess
@@johnpowers1125 I'm glad I have a standing seam metal roof where the risk of leaks are very low.
This is the problem with closed cell insulation, you don't see a roof leak. So, open cell allows condensation to rot the roof, while closed cell allows a roof leak to accumulate moisture.
Insulation above the roof helps keep the wood from being cold enough to condense. Open cell below it helps a roof leak to be visible instead of rotting the structure. There are roofers in the US who won't repair a roof with spray foam below the roof line.
That's not the foams fault.
What I like about your work and content, Matt is that you know code but you also have a very extensive knowledge of the science, which sometimes is ahead of code.
Hi from the UK, the UK gov has a history of 'insulation' programs that are used as ways to make jobs. A lot of people who dont have skills end up with low paid jobs insulating houses, there are good people doing it but there's also a bunch that pop up just to sock up the government money before the deadline ends.
It always ends up with a lot of problems, it's a rush to get the grant money over a real care for the work.
We have the same situation here in the USA. The government has weatherization programs that are largely staffed by unskilled workers that are poorly trained and have no basic understanding of physics. These weatherization programs often lead to homes having mold, moisture and IAQ problems.
In addition construction quality in th UK is way below the rest of Northern Europe when it comes to older houses.
Welcome to capitalism ...
@@3nertia Wrong, welcome to perverse government incentives.
It’s also a UK class E combustible, (not great) Polyurethane spray foam is nasty noxious foams at higher temperatures.
Anyone who installed as part of any insulation program, should be up for fraud and anyone who has this in are rented properties loft and not ripping it out should be up for corporate manslaughter if the property does a Grenfell.
America needs to establish serious trade schools that specialize only in residential home construction. Offer a graded certificate for proper completion of the required course load. Homes are too expensive to have knuckleheads being taught by other knuckleheads at homeowners expense. In my opinion knowledgeable craftsmen are in short supply.
Nah, architects and engineers should be liable for overseeing key details in builds and hold liabilities for them. Municipalities should also be on the hook for inspection failures. Bank should own the mortgages and not be able to bundle and resell them, and “as is” sales need to be forbidden by lenders/insurance companies.
You would think, right? Every restaurant has to have a certified Food Manager on site when the health inspector walks in. Every home build should have a certified builder on site supervising at all times. That could be your "lead" carpenter.
@@tsicby lead carpenter use to be called an architect.
Open or closed is bad for roofs. Issue is that if the roof has a leak, its make be impossible or very difficult to locate it. Water will pool & rot the roof. Either batts or cut peices of rigid foam panels should be used instead. You can always remove them for inspector or roof repair.
I suspect in the next 3 to 7 years there are going to be a lot of US homes that need roof replacement caused by spray foam.
My insurance company said nope to spary foam on the roof deck. So did the inspector.
@@homesteadhaven2010 where in the country are you, and why exactly did they say "no"?
wrong.... we found a leaking in a 2024 new build with open cell phone. i have pictures if you want to see it
@@chaunceyspencer great you want a prize with that? Sure you can find leaks, but likely after its been leaking some time, unless it a huge leak, & the spotted leak might be in a different location.
That said, Insurance companies will probably drop homes with spray foam at some point. So good luck with that!
I suggest building a better roof...
I'm from the UK and the house I'm in had this. The survey report was basically what you said, so nice analysis there. In the end I offered the seller £20k less because of this and I had all roof tiles replaces which was quite a big job.
Hi from UK.
Really interested to see this video Matt. Our Health & Safety Executive (HSE) have just issued a report on spray foam (no idea why as there is no H&S implication).
They say that the risk of rot varies according to roof construction, type of foam and and climate, but if done properly is not a problem.
Open cell seems to be preferred here, theory is so that moisture from below can pass through newer style breathable membrane as opposed to traditional impervious bitumen underfelt plus double height roof battens to ventilate under the slate / tile.roof. The HSE also advise open cell. Nothing is said about thickness or whether rafters should be covered..Vapour barriers unclear. Its just a mess.
I read that just one senior surveyor set this hare running, as he came across a couple of rotten roofs, and now everyone is running scared. The standard foam thickess used here is only about 4".
There is a bad history of closed cell being applied directly onto the underside of tiled or slated old roofs to "hold it all together" to keep the roof going past its life. Thats not good.
Cowboy operators bolstered by well-meaning government grants, have applied the wrong foam in the wrong sort of roof in the incorrect way, and badly.
Building techniques in UK have been changing, warm roofs are now a thing but that is fairly new. The more common traditional cold roofs need lots of through ventilation, with only 300mm rockwool type insulation on the loft floor. Lots of strong anti-foam opinion over here!
That lines up with so many stories I have heard from England on buildings. The regulators are extremely slow to address new tech, and by the time they do there are huge issues. And very aggressive opinions on it.
Like your comment on closed foam, it is great stuff if used correctly and not to cover up structural or other issues like you pointed out. So now closed has a bad rep because of it.
@@darkshardrex7589 UK doesn't do prescriptive design codes. It's very subjective with objectives you should produce. And as the Grenfell Tower Fire showed, there are a lot of people in the UK confidently doing design and construction very wrong. who are overseen by inspectors who apparently have no idea what they are doing and standards bodies in the pocket of manufacturers.
and that's the truth.
I just don't get why the UK can't learn from decades of experience in other jurisdictions.
@@rsmith02I'm afraid the UK are right on this one, spray foam is bad on so many levels in this application.
Surprising that this happened when there is such close tech exchange between the UK and Scandanavia. Cheers and thanks from Northern Ontario.
I think you missed the comment where she said that she had black mould prior to the install. That is very common here, and indicates that there was already a problem with condensation to start with. The high humidity here means that people don't really trust wood buildings.
One of the issues was the way that the grants were structured - it encouraged companies to quickly do a lot of installations with minimal / no training of the staff, and no consequences if something went wrong. So it did not matter to them whether or not the roof rotted afterwards.
Absolutely. Humidity is sky high (70%) and in winter people do not open windows (even in bathrooms) and few people use dehumidifiers.
@@ChrisLubinskiwow, 70% humidity in winter?
@@Ed-ym4tu Average humidity for the last week outside was 96%
@@Ed-ym4tu Usually significantly higher than 70 in winter, frequently in the 85-95 range. 70 is probably the year-round average.
This is a good example of what I've noticed in the trades since the 80's. A new code, a new material, or new SOP is introduced into the industry and contractors try to incorporate it without understanding the full scope of how it effects the overall build. In our area in Southeast Missouri in the 80's the contractors were trying to figure out if they should use plastic sheeting behind the drywall because we are a "cold" climate, so if they were doing it in the North, maybe we should too?? Because we are actually a "Warm/moist" climate it became a problem, however, I know of buildings that were built as late as 2009 that have plastic behind the drywall as a vapor retarder. Understanding cause and effect is sometimes a slow progression.
I've heard of crawl space capsulation projects where homeowners started getting headaches afterward, then after cutting out the vents and re-introducing fresh air into the crawl space the headaches went away....Most likely they did not have proper ventilation to bring fresh air into the house, once capsulated, stack effect slowed down or stopped bringing fresh air in thus causing an air quality issue.
The point I'm getting to is summed up into a saying I heard from a site works guy , he said: "Change the dirt, change the water". When you add or change a system in an existing condition, you change how other systems work. Unless a holistic systems approach is applied and designed into the changes, most likely there will be a failure. Stick to existing SOP and materials of the era the building was built in, or completely change all the systems so they work together....
Sadly, when something fails and insurance companies start paying out large claims, they have enough power to motivate changes and vilify materials and SOP. They don't care if it's an application problem, they just want to stop the losses immediately. Education in all aspects of the industry is desperately needed!!
Yeap. Total ignorance pervades society and most trades. There's like 5 people who know what they're doing.
Love that wisdom, thanks!
I’m not a fan of anything “permanent”. If you can’t disassemble what you assembled, you can’t fix anything.
I agree with you and like your comment. Question: Are you also a bit older? I only say that because I have been a building contractor for about four decades and have seen many products not hold out as represented. A popular product "PEX"warranties 25 years, copper 50 years. 25 years is not very long buried in a wall of your home.
Absolutely correct. I live in an 80+ year old home and have been able to renovate and repair much of it because it’s all accessible ( water damaged fiberglass insulation, insulation in the wrong places, leaking pipes, substandard electrical wiring, etc.). If any of this was inaccessible, we’d be looking at a demolition and rebuild. Radiant heating embedded in concrete? You are putting a lot of trust in something that will be a nightmare to fix if it fails.
@@janking2762 Very true.
@@fsoileau I respectfully disagree with your Plumbing analogy. We don’t know the lifespan of PEX yet. Just because the warranty is set for 25 years doesn’t mean it’s not good for longer. We’ve all seen copper lines that are well over 50 years and are perfectly fine.
I have seen copper lines that were installed touching a dissimilar metal and have corrosion to the point of failure. It comes down to how it is installed same as PEX
I work for a pest control company in Florida and we will not warranty a roof if it has spray foam. If termites get into the roof deck or trusses that are covered in spray foam their is no way to inspect it and know. And if you fumigate a house with spray foam their is a chance of gas being trapped in the foam. Not recommended anywhere drywood termites exist.
Matt, here along the Gulf Coast in the US, non-native Formosan Termites are causing a LOT of problems. And the closer to the water you live the worse it is. Recently, I wanted to upgrade the insulation in our attic from fiberglass bats to spray foam. But I quickly found out that our termite company (Terminix) would drop us (cancel the bond) if we installed spray foam - for fear of trapped moisture which would in turn attract termites. Called other pest control companies and they said the same thing. Talk to your builder buddies in Houston about this. It is a BIG deal along the coast as every single home on or near the water has had a Formosan termite infestation. The Formosan termite colonies are an order of magnitude larger than normal subterranean termites and so they eat a lot of wood in a short time.
Good to know, I was always a little sceptical about this.👍🏝️🇨🇦
😯
I've never seen any insects in foam. I have seen it in every other type of bat insulation. They love to nest in that stuff and once it gets wet it never drys out.
@TheWhale45
I've seen insects in foam. Insects that because encased in foam because they were hiding out in crevices when I shot the foam. 😂
We should build a wall and keep them out
You always have the best information about home building around. Thanks for looking into that. Love your channel.
So nice of you. Appreciate that
The problem I have encountered repeatedly in the US is that finding a good installer is incredibly difficult. It’s hard to know if people are doing things correctly unless you yourself are an expert. Had a mini split install recently where contractor made a subtle mistake welding (edit: not welding, brazing) the line set and this caused thousands of dollars in damage to the cassettes. The install LOOKS great. Inspector didn’t think to ask about it. My concern is that mortgage brokers and insurance may lump everyone together and cause problems for modern homes no matter if Matt built it or not.
I just made a comment about the lumping together. Big companies seem to do this quicker. Might have to seek smaller insurance co's to get coverage. Good to still be able to get coverage but limiting options isn't great.
Welding the line set on a mini split??? 🤔😯
Let's be honest. In some areas of the construction industry in the US far more than half of the workers aren't even supposed to be in the country in the first place. Of course they're going to take any and every shortcut available to them. Most of them don't even get paid per hour but get paid for job so the goal would be to do whatever you're doing is fast as possible.
@JustNo8808
You know what, l can be honest too. I've worked with a bunch of these guys over the years - talking about construction workers you pick up at home depot or wherever for day labor - work by the hour, get paid in cash at day's end. I don't know that they were all undocumented but no surprise if they were. The point is, they frikkin work. I'm sure there's exceptions but the guys I've worked with were friendly, respectful, focused, followed instructions, asked when unsure, and strived to do the work as expected. We'd get their numbers and call them back whenever needed for more projects. They were cheaper and better than calling some established subcontracting company that might get to you the Tuesday after next and then be delayed, and when finally on site do things their way instead of how we wanted it done. Americans literally did this to themselves; I'll take hispanos all day long!
(That doesn't mean I'm for illegal immigration; I'm not. I'm for LEGAL immigration and carefully vetting everyone allowed to immigrate. I'm looking forward to the incoming administration sorting out the mess of the outgoing admin)
Yeah, not sure what that means.@elgringoec
Wow. Amazing investigative work. You probably hit the nail on the head.
You pretty much got it spot on. Good explanation. We have very different houses in the UK. Mostly clay tiles, poor insulation.
Great video! Thank you for making sense of this otherwise click-bate headline. I'm glad people like you are willing to do the work of what the old media used to do.
Having lived in the UK for over a decade, coming from continental Northern Europe, the type and quality of construction in the UK is shocking. It’s not only the cold climate, it’s the year-round humidity, and that they absolutely weren’t building for it.
Your comment that some house are “under-insulated” made me choke. There are buildings here as recent as 40 years old that have either 2-3 brick thick solid walls, or a 2 brick thick wall with a totally empty cavity in between. No underfloor insulation, no roof insulation, just the expectation of cheap natural gas for all eternity. To the point that the only way to adequately dry out your house is to have heating on 24/7.
The spray foam roof insulation ‘scandal’ is the result of an endemic culture of short-sightedness coming home to roost, not only once (when originally built), but twice (when foam was installed). New requirements here finally got higher air tightness and requirements for mechanical ventilation (ERV/MVHR), but even then the homeowner rarely understands what it’s for, what it does or how it’s supposed to work… much less maintains it properly.
The UK's maritime climate means that an indoor RH of 50% and upwards is common.
@@tlangdon12 Yes, well said, and most people would not have a clue !
Houses in the UK are cold, drafty and damp. Been that way since the Romans left. At least they gave up on high sulfur coal.
@@johnm7249 Yes, those are the predominant features of many UK houses! But we can build warm, dry homes that are ventilated adequately but are not draughty.
I lived in the pacific northwest, namely western Washington state, which has a very similar climate to the UK. I remember living in cheap apartments with electric baseboard heat and aluminum windows that conducted cold and damp. I also attended the old Union Trade School, presently run by Seattle Community College, for two years (1993 to 1995) for carpenty and fine furniture. We got to work on several remodels including two gut jobs down to the studs. I have also owned 3 houses in the area, including my first house which was built in 1928 and my last house which was built in 2008.
Vapor barriers for the crawl space were taught while I was in school. We were trained to apply a vapor barrier between the exterior sheathing wall (normally plywood or OSB) and the exterior cladding. All the remodels I worked on used paper-backed fiberglass that had an edge to staple onto wall studs / roof rafters. Over the top of that we stapled a plastic vapor barrrier.
They may not be the most attractive but double vinyl windows are excellent insulators and the vinyl prevents excess moisture and is easy to wipe down and clean.
My last house had a gas heat pump for botth AC and heat. This was the cheapest form of heating and AC and very effective. The air inside can become almost too dry in the winter, however. This house, built in 2008, also had a number of evenly spaced roof vents and a whole-house exhaust system built in to pull in fresh air from outside. I think there were also attic fans, as well. This house was highly efficient and I never experienced any mold or damp issues.
Thank you for taking the time to explain this issue.
Howdy from a Texan ex-roofer (with young knees LOL) that lives in France but previously all over Europe/ME. First problem is that Roofs are NOT built like in the USA ... where we install plywood/OSB over the trusses and then apply a tar paper layer before asphalt shingles. Here it is def "open air" with clay tiles resting on batons and nothing but the wild blue yonder between. Throw in high winds (especially in the Athens area of Greece where I even lost tiles in high winds) in rainy conditions and you've got a "colander" type roof; your reference to 1x4" might be typical in the UK but nowhere else. Also keep in mind the Trusses rest on cinderblock or concrete wall structures; in Israel, the roofs are solid concrete in some cases ... sort of required in a Country where EVERY house/apt must have a "Mamad" or bomb shelter of high KSI reinforced concrete and it ain't just "rain" coming down like now. On a side note, Hurricanes and Tornados don't really cause much damage and the USA should learn from this construction method ... not much more expensive for new builds but would require a re-train of our crews ... much different approach.
Anyway, I'm with the Insurance Companies on this one ... if the roof isn't sealed, rain/dew will certainly shorten the life span of the trusses/timbers as the spray foam is on the wrong side of the equation (trapped) ... "black mold" is worldwide BTW. So on a retrofit, clay tiles need to be remove, plywood/OSB installed and tar paper laid before reinstall of baton/tiles. "Governments" ??? What are ya gonna do??? Same ones that allowed "Lead" to be added to our Gasoline back in the 1920's just to quieten down valve trains ... not well thought out. We'll see how Solar Panels fare. Cheers.
Very informative comment, thank you. I've seen a few videos in the past about concrete homes and wondered why they weren't more popular. Seems like they would do better in severe weather. I'm not a builder, just curious.
As I see it, the issue is ventilation. Provide adequate roof ventilation, and this should be a non issue. I don't think it has anything to do with using osb sheathing. And almost nobody is using "tar paper" anymore... nobody who builds quality anyway.
@@TimTimTomTomI just took the tar paper off my 100 year old house and it was in great shape. Replaced it with more tar paper. I'm not convinced tar paper isn't quality. 🤷🏻♀️
@@TimTimTomTom ... and you live where? Want to nit pick over tar paper vs plastic wrap or plywood over GP water resistant sheathing ... everybody's got their opinion. But my point was neither is used traditionally in the UK or EU ... and when the wind/rain is coming at the roof horizontally, all that water will be trapped in the foam barrier instead and initiate rot; the reason for the content creator's post.
Let's be clear about "tar paper". I am 70, worked in construction before retiring. I have seen very few houses with actual "tar paper", and those were old houses. Newer construction ( most of my lifetime) uses "felt", which a lot of people confuse with tar paper. I had my own roof replaced in 2014 and they stripped and reinstalled 30 lb. felt, before laying the fiberglass shingles. Not putting the felt is kind of foolish in my mind as it insulates ( however slightly ) and provides additional barrier to water penetration should any get through the roofing.
Thanks for depth follow thru telling me exactly how much closed cell foam I need !
Here in Norway we basically don't use any spray foam. It's seens as toxic, worse when it comes to fire and higher risk for water damage. I think all of the Scandinavia is the same
th-cam.com/video/w-MsPTD_14s/w-d-xo.htmlsi=ZbLqM4XhqQhrcoQ8 you don't say
Here in Finland I use cellulose insulation in the roof of my log house, and no vapor barrier - only a permeable air barrier. No issues with moisture build-up and easy to check for potential problems.
@ yes, real vented homes seems to be more back up here in the north now. See more and more of that kind of insulation
Rockwool is best.
@ jeg kan personlig ikke fordra å jobbe med rockwool, men det er mange som sverger til det.
Thank you Matt. This is the technical info i wanted. I knew there was a logical approach to condensation in living spaces. Keep it up dude
Matt, most of the pre 1920 properties in England are slate or clay tile fixed on timber (lumber) battens fixed directly to the top of the rafters with no underlay, roofs then started to include a layer of roofing felt below the battens with this becoming the norm from about 1950. The use of timber sarking boarding above the rafters was generally only used on higher quality/status buildings, it has only become more common on domestic building recently, especially where there is habitable accommodation within the roof space.
Spray foam only really began to be used in England from the 1980's and then generally only for retro fitting, its use mushroomed about 20 years ago when there were government grants available for installing insulation to older properties, this attracted many unscrupulous installers with little building science knowledge to promote it for totally inappropriate situations who then often had very poor inhalation procedures.
yup inhaling foam is bad for you.
I love how Matt mentioned " home building scientists". Matt, we will look back at this foam craze and truly shake our heads. I have been against foam in any form(open or closed) since it was introduced. If you ever have to dig into it, it's a disaster. If you don't install it properly, off gassing. Leaks happen and closed cell will hide issues until it's too late. Let's be real, a lot of issues are from install error. 90% of installers will make an error. It's just not worth the risk. Just like the Govt in the UK pushed it and now are backtracking, it will happen here in the states. You can be a scientist in home building, BUT, my man, I have common sense and 25 plus years of working in every type of build up and down the east coast. I've never seen a build, regardless of price and said, this is perfection. It does not exist in 99% of the home builds. Unless its you or a this old house budget. That's not the norm, it's the exception. The codes need to chill out or our housing crisis will compound and get exponentially worse. The r requirements are getting out of hand. Your videos with stacks of insulation on the outside and inside are RIPE for major issues for homeowners down the road. Too many layers to hide disaster.
Agree 1000%. It's a rubbish product that we all will hate in 20 years. Short sighted once again
Exactly! I would rather have many good failsafe options instead of a single theoretically perfect ultimate.
Instead of thinking like a wise military mission planner and having answers in advance for likely errors in execution these foam projects have almost no tolerance for errors.
I don’t know how Matt sleeps.
While properly installed closed cell insulation with no leaks will solve the problems from vapor condensation, It can greatly increase the risks from bulk water from above when the roof fails. Yes, some people replace the roof when a periodic roof inspection indicates that the roof is close to end of life, many people first thought of roof replacement is when the brown stain in the ceiling gets larger and may take a year or more to figure out how to pay for it when they get an estimate of the cost. By that time, it won't just need a few pieces of roof sheathing replaced, it will need much more sheathing which is still glued to the insulation where it hasn't rotted to mulch and roof rafters with it. Won't it be fun to rebuild those trusses. Much of this damage will be done before any water gets through the closed cell foam to leave the brown stain on the ceiling.
Excellent comment, anticipating frequent human behavior! Imagine that!
The Perkin Brothers had a similar issue with the insulated foam forms used for concrete walls and basements. The termite guys would not warranty it so the bank would not finance it. So they did a video about it to warn other people about the potential problems they could face if selling or refinancing the house.
No one who's ever had to fix a leak on the other side of some polyurethane foam wants to do it again.
I've seen someone do a fire test on that spray foam and I've gotta say that in a fire it actually boosts the flammability of the house. See the heat melts it and it just turns into oil which burns hot and helps keep the fire going and spread.
And is probably more toxic
This is part of why I never understood why people love it.
@@wobbuffetbuffet Because its cheap and fast to install.
@ADobbin1 Not cheap though.
@@ADobbin1 Well, i was told it is fire retarding, that was one of the reasons i used it..
There was also an episode of Holmes on Homes, or another Mike Holmes show I believe where they removed everything due to the spray foam installer spraying the foam too thick up in the attic, thus it would never fully cure and was slowly constantly outgassing, which was making everyone in the home sick.
as a foam applicator your correct
@@stephenmitchell4393Technically correct, but could be misunderstood. So people understand - this has nothing to do with how many inches are applied in total. The problem arises when the applicator moves too slowly or over the same spot too many times before the foam can cure. Uncured product can get trapped behind cured foam and stay that way. It usually smells horrible, and therefore isn’t a danger because it’s caught.
@@nunyabidness3075 Right, as there is a difference between spraying 1 thick application, or spraying multiple thinner applications to create the same thickness.
Mr. Risinger, thank you so much for sharing this informative video! I have lived in northern Florida in a century-plus-some home for the last quarter century. As both the house and I have aged and the winters have gotten harder on us, I have frequently wished to insulate the uninsulated house a bit better. However, throughout my life, I had noticed that older houses without insulation and with well vented attics and metal roofs seemed to last forever, while newer houses with well-sealed roofs of any sort seemed to develop issues in only a decade or two. I thought condensation might have something to do with it, but I could not figure out why it was so much more harmful one way than the other... nor could I figure out how to insulate my attic without damaging what has been working for a hundred years, albeit in a chilly manner. You helped me immensely to understand which pitfalls to avoid, and how I might safely proceed, rafter-wise, by explaining the thermodynamics involved so clearly, by including great video examples, and by providing all of the relevant related specs and information about various materials at the same time. So, much gratitude from Florida, indeed! (Now, I just have to figure out what to do about the floor... Is it better to dig out and replace the unvented underpinning all around the crawlspace that stagnates the air beneath the house, and then replace it with breathable underpinning to let the air flow underneath.... to perhaps help inhibit the mold that seems to come up from below, underneath the sections of old linoleum? Is that moisture maybe from the higher water table beneath our Florida yards these days? Or would it be better to install a vapor barrier between the ground and the joists, and keep the underpinning intact to seal out the fresh air? Perhaps you already have a video for that too... I must go check!)
As a UK PassivHaus architect and project manager, I applaud your channel. I have been advocating that we need to build more like Americans here and move rapidly away from the so called traditional methods favoured by UK contractors.
I would strongly disagree with you, from experience of being from the UK and having family in the USA we should not be copying them.
We have historical and economic reasons not to build in timber as the supply is not local and costly in comparison to the USA.
Matt also references Dr Joe Lstiburek constantly, and rightly so.
If you watch his lectures on the perfect wall or the institutional wall which will last and provide good performance for centuries then he basically describes the UKs standard brick and block cavity wall used in most houses today.
Architecture jumping on the latest fad, like timber frame construction also cause reactions in regulations like the new part O, or overheating.
Ignoring the fact that it contradicts part k and m for window guarding, the elephant in the room is no consideration is given to thermal mass in any of the calculations required for building control.
This is not the case in Germany for example and makes light frame construction look great on paper but it's an illusion.
The USA are heavy users of aircon, but with thermal mass it just isn't required especially in the UK where problematic hotter weather only lasts for a few weeks at most.
The Romans knew it, the Greeks did, they still use it in the middle East and some parts of Australia now.
A couple of years ago with 34c outside my living room 1910 cavity wall direct lime plaster on engineering brick with 150mm natural yorkstone exterior with a 30mm cavity didn't rise above 22c as tracked by digital thermometer and humidity sensors.
My mostly timber framed well insulated room in the roof however didn't drop below 30c
My point is copying someone else's homework for English literature may not help you in a French class if you get my meaning. The UK and USA have different resources and climate conditions, resources and physics dictate what will work economically not fashion.
@ follow the building science. And building in brick is cheaper??? 😂
@@colinmendelowitz249 no brick has nothing to do with it.
In fact a lot of the house builders are looking to go timber frame as that's cheaper!
The performance though is inferior in most ways other than speed of build and possibly air tightness but that's debatable.
@@nathanlegge7090 Thermal mass is indeed a good thing, but it's also usually very high-carbon. There is a tension there. It can be offset by very long lifetimes. Passivehouse says nothing about timber vs brick vs concrete vs whatever - it's all about building physics that adds up. And it removes any issues with condensation in the wrong places, and makes very comfortable houses with tiny heating loads, that don't overheat. The art is building good houses without an epic up-front carbon cost. Less brick and concrete generally helps with that, but stone can be very low-carbon if it's not had to come too far.
@@nathanlegge7090well said!
Love you, Matt. Great video. UK =England, Wales, Scotland and Northern Ireland. Also, mold is really prevalent in most of the UK. You have to wipe your windows off once a week. Homes have “vent bricks” which is basically an open hole through the wall for ventilation. No forced air heating, only radiators. Many families dry clothes on the radiators. No where will you find under 45% humidity. 60-80 is more the norm inside homes. No one in the UK should be surprised by mold in their home.
You have missed the point why the mortgage companies are unwilling to lend on spray foam insulated houses, while doing a great job of explaining the science. The issue is that the roofs with spray foam are hard to inspect for issues (especially caused by damp) and together with a significant number of poor installations this has led mortgage lenders to refuse to deal with spray foam. The idea of mortgage lenders or insurance excluding certain categories because they are awkward to deal with is certainly something that happens in the US, too. It doesn’t have to be spray foam insulation.
The next problem is most of these houses have to pass a blower door test when they test for air tightness, the regulations are getting tighter. I’m seeing some builders not pass the DET(duct envelope tightness) test because they didn’t spray foam.
If states want their houses to get tighter without spray foam….a lot of builders arnt going to get their certificate of occupancy. It’ll be the builder apocalypse
PEX is an example. I've gotten quotes from a few insurance companies that will not insure with PEX plumbing (and no, I'm not confusing it with PB).
Properly installed closed-cell foam can be a real boost for increasing the durability, comfort, and energy efficiency of the housing stock. Eliminating that option by refusing to insure it, is a bad move _in the long run._
In the short run it makes sense from the insurers' point of view, for the reasons you stated. What needs to happen is that the UK government needs to have more demanding education and training for insulation contractors, so that they know the right way to do things. This applies to building inspectors as well.
With the contractors properly trained and regulated, the building failures won't happen and the insurers will be able to take on an appropriate risk level.
@@MrDbraultwhat is their issue with PEX? the only issue with PEX is not installing the fittings correctly. Assuming the job was done right, it's good for a hundred years.
@@Tr-mx3qs It's a lack of imagination to think that only spray foam can deliver an air-tight house.
When I had a “tar and gravel” roof replaced, I had the roofers install a LARGE thermostatically/hygrostatically controlled fan installed. It comes on when attic temps are above 90’F and when relative humidity is about 90-95%. The fan runs a lot in summer from the heat, but occasionally in the winter when we have damp foggy weather outside with dropping temperatures.
People don't understand how important proper ventilation is.
It's an unvented roof assembly.
It's not important if it's sealed. That's the point.
A popular phrase I've heard:
Seal tight
Ventilate right
Yep we seal these up so much that the fresh air that used to permeate the envelope needs to be introduced mechanically.
The general public don't understand how important it is, but professionals for the most part do.
Build tight ventilate right is a good catch phrase but you have to know the likely failure modes and mitigate them.
Older designs have had hundreds of years of evolution to be perfected with local adaptations used for local climates.
Foam insulation, chipboard, osb and to a lesser extent plastics are getting that evolution now and it's proving some to be not up to the task or causing secondary issues.
Construction is quite conservative in it's approach for good reasons as the consequence of failure can be very expensive
Here in South Australia we have an airtight envelope, as its so dry [8" per year], but still got a vented roof space, above the envelope with height of 7'. Self Designed house. LOTS of research first.
Great video and super-helpful presentation of the available facts and info-thanks, Matt!
One of your most informative videos….thanks for sharing
Glad it was helpful!
Great treatment on this topic... I'm originally from USA and have been living in UK for 11 years... it's horrific here in terms of damp and mold problems. The average humidity level in most homes in UK is above 60% for example, which drastically alters that dew point you spoke of so it happens much more easily. Further, even in homes using ceiling level insulation and no under roof insulation as should be done here, many of them do not have proper venting of the attic space, it's all closed in. I guess it is to be expected, the UK gov was until some point in 90's telling their citizens to vent their clothes dryers into their homes to help heat the home! After decades of doing that they then discovered the massive mold and associated health problems it was causing and stopped recommending people do that, which then became a recommendation to use condensing dryers. These are better, they do still provide a small heat boost, but they also still do put some additional humidity in the home... how much depends on the dryer and if it's condenser is being maintained properly.
I live in the UK and never heard that the government advised to vent dryers into homes. All the advice I saw was to run a vent duct outside except for condensing dryers which are relatively OK to vent into the room - but only just.
The real problem in the UK is that many homes have the kettle running almost 24/7 boiling water for the copious cups of tea consumed 🤣🤣🤣🤣🤣🤣🤣🤣
I'll venture a guess that no dedicated vents were needed when the tiles were just laid on battens, but with more felt and other barriers, the codes for venting didn't keep up with the changes. Here in the USA, vented roofs have a generous soffit openings, but with vinyl siding and foam sheathing popular in colder areas, that makes it very easy for a fire to migrate from a window to the attic, destroying a house in 10 minutes.
Hi Matt, UK roofs typically for the age you are talking about and even modern builds are felt underlayment, battens and terracotta tiles, plywood sheeting is not normally used. The loft spaces are built as cold roof, modern (last 30 years) will have ridge and soffit vents.
Worth noting building regs are different in Scotland, where sarking boards (i.e. wood sheeting) is required.
Thanks Matt - always great content and great research.
Well nuanced vid, Matt. I'm glad I'm subbed.
Thanks for the video! I’m a huge fan of closed cell foam. Have used it in a couple personal houses I’ve built and lives in within the last 20 years. Great stuff!
I will mention based on my research I did on spray foam 20 years ago talking to the spray foam engineers in TX, they said the north in colder climates is where foam was first adopted, so I don’t see that being the issue.
I agree with you, as I know for a fact, when the foam doesn’t adhere to the side of the rafter you get condensation. That’s why my foam guy used caulking to seal the edges of closed cell foam to the rafters where small gaps were at.
That house looks more like 90-100 years old rather than 40. Roof structures in UK are generally very different to US.
"Under insulated" is an understatement.
Recommended ceiling insulation in UK is 300mm (12"). Normal is fibreglass.
Tiled rooves on tar paper with battens is normal and as you say relatively breathable.
Your homes in the US are very different.
Hi Matt, as a carpenter in the UK we dont usually sheath the outside of our roofs like you guys over there. We have our roof structure which we then cover with breathable membrane and then batten and tile with slate or concrete tiles.
A lot of the time when this type of insulation was used it was sprayed straight onto the old style bitumen roofing felt which also isnt breathable. There is also a lack of knowledge within the UK trades with reference to insulation and air tightness. Unless we are doing passive house stuff there isnt really much accountability.
We need much more of a investment in the trades to bring in the knowledge of building science
Cheers from Canada. Been a guy who has built 2 - R2000 homes - 20yrs before they were adopted. Working on a NET ZERO. heavy insulation wall and ceiling, Double 1980 standards. It was a response by NBPOWER executives to the 73 OPEC crisis . Our area - is - 50 F. We need to release water - and decrease moisture into the house. For years - I have used - forced air movement. Thank you MATT - cheers!
Check out “ this old house-net zero bungalow, season40” believe it was based in Rhode Island, not as cold as you wrote but was a pretty cool build.
Lived in England for four years, and owned a house for three. Our house was built, I believe, in the 50s or 60s. There are a number of paradigm changes with British homes. For the most part they weren't insulated at all. There was also no such thing as central heating. There was a coal fired fireplace in the sitting (living) room, and the door was left closed in the winter, so that was the only heated room in the house. That worked for them because it didn't get all that cold there. Being spoiled Americans, we wanted it warmer. There was cellulose insulation in our attic, but I don't know if it was there originally. We paid to have foam insulation blown into the cavity between our outer wall layers. They didn't use wood in the walls, so this wasn't a rot producing problem. We also had double glazed windows installed. It wasn't as warm as an American house, but it was far more comfortble. They didn't have pressurized hot water either, so you couldn't get warm water from a single tap. You had two separate hot and cold taps, or a 'mixer' faucet that was just two water lines close together in one fixture. It never truly mixed though.
Lived in the UK for a bit, can confirm. Huge caveat, the UK builds homes very differently than the US.
exactly.
@12:30 Matt is exactly on point here. My 100yo house near Boston was built EXACTLY as he describes it. Rafters, then 1x, then tar paper (cracked) then slate tiles. Yes it's slightly leaky. There is no way in hell I would ever do what my neighbors did and foam up the rafters (with closed cell). That's a disaster waiting to happen. According to several prominent building scientists, you're better off leaving it that way OR install baffles and then foam. Best is to replace the roof and install proper WRB.
So I would say YES this problem is coming to America, in some places, mostly in the North-East and in particular New England (ironically).
Lol @ 'ironically'
I live in South Florida and I have had to do WDO inspections for home refinance. There has been issues with homeowners Who have put in spray foam insulation and cannot get bank approval.
For the most common reason of it, making it inaccessible to see if there is or was termite damage that's being hidden/ iconcealed by the insulation. It also prevent us from being able to treat the exposed wood throughout the attic in a preventive fashion against wood destroying organisms using profucts like bora-care or premise2.
Great informative video!!! The facts matter! Keep it coming!
Good job. You may also want to look at the HSE (Health and Safety Executive) document referenced in one of the articles titled Spray foam insulation applied to timber sloped roofs in dwellings Modelling of moisture risk for retrofitted spray foam insulation in existing dwellings. They did the computer modeling and determined the risk.
The roof you have described, with some tar, is exactly what I have in the UK.
The main problem I see is that the internal spaces humidity isn't 30% in the uk in most homes. More like 60% in many older homes. So the dew point is really low.
I believe you were underestimating the average relative humidity in the UK. In addition to that due to the high relative humidity outside, there’s going to be a certain amount of water vapor that penetrates the roof and is then trapped between the foam and the roofing material. When the temperature drops there’s not time for the moisture. to escape, and consequently will condense.
Hot dog! This is a great combo of tech and layman terms! Matt, you hit it!
Canadian Home Inspector, Canada, good to see your video, thank you. Open cell foam must have a proper plastic vapour barrier, open cell is not used often here. Also I am aware of anyone insulating thier roof interior unless the room has a candretha ceiling. our insulation standard is R60 or 17" of blown in insulation, this is laid on top of the ceiling. I fthe home uses spray foam then it must be closed cell.
alot of roofs in the north are like. u said. big attic space and r60 blasted fiber glasses or cellulose blown in insualtion.
We always depressurize the building with a blower door and do a thermal imaging QA review of the foam in the roofline. Every imperfection we find the insulator marks with paint for touch up/correction. We find imperfections on 100% of the jobs as it comes with anything that is manufactured in mid air and at high speed :-). We believe this QA process is critical to the long term integrity of the roof deck.
Good video, the conclusions are good. You are low balling the humidity in the UK. Depending on time of year and location it can vary between 50% to 90%. Most roof construction is roofing felt on top of the rafters you see in the videos with batten nailed on top of that to hang the tiles from (tiles are nailed as required by building regulations) so not a lot between the cold tile and the inside of the roof space, nothing you would recognise as a deck. The big problem with this sort of work is the government grants for it. Companies will convince people that the the new (funded) thing is good for them and do the work, then get paid by the government irrespective of whether or not the house is suitable for the work or not. This behaviour repeats with each new government initiative to improve the (elderly) housing stock of the country.
FYI, the UK is relatively humid. Expect roughly 60% humidity indoors even with some use of a dehumidifier, and 80-95% humidity in an uninsulated loft. Even without spray foam involved, it's very common to have condensation issues if additional ceiling level insulation is added, cooling the loft. Middle-aged housing stock (say 1970s) has non-breathable bituminous sarking felt under the tiles and typically relies on gaps at the eaves for air-flow - which may be blocked by extra insulation or boarding laid down for storage. Without adding felt lap vents or ridge vents, it'll be raining inside just from warm moist air leaking into the loft and condensing.
Makes it easy to see why spray foam would be an issue. You're still getting warm moist air escaping into the loft, but now it's condensing right at the rafters with no ventilation to dry it out, migrating through the foam as you say. And if you encapsulate the rafters, no-one can inspect to see if any water is getting through the tiles - so neither open-cell nor closed-cell foam is really acceptable for a retrofit.
I agree with the humidity, as a Brit who moved to Massachusetts it is incomparable. 60-70% compared to 30-35%. Also the weather, it pretty much rains or is damp every day in the UK from November to March. In Massachusetts in December to February it is super cold but dry.
Another thing is Brits tend to air dry their clothes in their house, Americans just use a dryer as electricity is so cheap, like 1/2 the price.
Homes in the UK tend to sit at a humidity level of 50-60%
Yes or more in the attic. But also the ventilation at the rafters is missing in many of these situations, so there is often no path for the moisture to be removed.
@emcguinn2601 exactly that 👍
Reading your responses to other comments makes me conclude, it's not the spray foam thats at fault. Let's be clear.
@mikeclarke952 to be pedantic: It's not the spray-foam, it's the position it's used in which is at fault.
In Houston, we have seen insulation companies add foam insulation to roofs in older existing homes, causing a lot of trouble. Excess humidity is due to their existing A/C system now being oversized, and the gas furnace is not operating correctly because they seal the attic.
I kinda have this debate often with people online. Spray foam is fine but you need to do a bunch of work first to make it acceptable, it’s best on new construction.
I would argue it's not fine at all since it traps every service in a permanent layer of crap which can't be recycled, reused, easily removed (if later renovations etc). The side of every leading spray foam bottle says "contains carcinogens", so I doubt spraying your home in the stuff is good for you.
Also only works with houses continously covered in OSB or plywood.
Great explanation matt! Thank you for this
Should probably be cautious of ChatGPT results when they don't have sources cited. Could just be completely made up.
Matt, thanks for the video. The 2024 International Residential Code, and its predecessors, deals exactly with this issue in Section R806.5-UNVENTED ATTIC AND UNVENTED ENCLOSED RAFTER ASSEMBLIES depending on climate zone. The issue that is being overlooked a lot of times is the air-permeability of spray foam. The IRC defines "air-impermeable" (for the purpose of moisture management) as "an insulation having an air permeance equal to or less than 0.02L/s-m^2 at 75Pa pressure differential as tested in accordance with ASTM E283 or E2178." Air-impermeabilty is used by the IRC in insulation to prevent condensation on condensing surfaces as described in the video. There are open-cell foams that are air-impermeable and closed cell foams that are air-permeable. Some open cell foams are air-permeable until they are applied to a certain depth and then they become air-impermeable. The details of each foam products performance must be observed and you have to dig a bit to find it. The details are in third-party evaluation reports published by multiple agencies, the ICC-ES (International Code Council Evaluation Service) as ESR reports (google your favorite foam), Intertek CCCR-Code Compliance Research Reports or UL ER- Evaluation Reports., etc. In my office we do not use the term OPEN CELL or CLOSED CELL as it does not accurately reflect the air permeability. The key for the consumer is to KNOW what is being installed.
I am in Canada... and I removed all spray foam... everything was rotted.
I have douzen of pictures of the mess
Was the issues the same as this one- gaps where interior air condensed? Or was it a roof leak?
A really incompetent self handyman
.... I can write a book on how to not renovate... with all I found hidden in my house
@rsmith02
The extention the house, block all the ventilation, build a roof over a roof... a total of seven layers of shingles on over the others on a 2/12 pitch...
And they use spray foam to hides everything
@rsmith02
So the leaking of the roof was accumulating between 2 ceiling... until everything's fall down
I’m an engineer and I HATE the idea of spray foam insulation for entire houses. It is super hard to put fires out, it can mold easily, it constantly off gasses which reduces overtime, but is still there. Not in my house. Only as gap sealer
I wouldn’t have thought that the humidity in a typical UK home would be anywhere near 35%. Do most UK homes use forced air heating that would lower humidity. The weather in the UK is typically humid and the weather is typically rainy almost like Seattle.
That number is way too low, try 60% as normal. No, forced air heating is not used.
Closed cell for my entire envelope. Circa 2007, new build, unvented roof. Home builder for 25 years.mid Atlantic. I've cut into sections for additions. 0 problems. As with anything, installation by competent professionals with proper conditions is key.
I put a layer of ridged foam between the decking and spray foam. If the decking needs replaced we should be able to peal the bad decking off without touching the spray foam. Time will tell though
Thank you for your analysis and information.
It can be moist but it must then dry completely because mold grows in consistently moist areas only. Excellent video presentation that really got me thinking.
Another comment regarding moisture control:
It’s my position that you will never be able to completely keep moisture out. Even if you did, I’m convinced the seal would fail over time. A “tight” house is a trap for moisture.
Instead, I focus on what I call “moisture management.” I assume moisture will get in - so I make sure there’s a Way for the moisture to get out. For example, I advocate installing siding with a small gap between the siding and the moisture barrier. That way, any moisture that gets in can drain out. I ensure there’s a clear air path on the underside of the roof, from attic vents to ridge vent.
Entirely depends on how you define "Tight." You can have a house with minimal air leakage while having that gap. Since it's outside the envelope.
@@arthurmoore9488
I roll my eyes every time I hear someone use the phrase “building envelope.”
Spray foam can definitely cause problems with trapped moisture ending up against the wood surfaces. The moisture can enter from above (roof leaks) or below (humidity enters and reaches dew point) as you pointed out. The interior moisture can penetrate into the wall or roof cavity from the interior, if the material's permeability is high enough, and then it is trapped inside with no place to go to dehydrate. Air sealing the exterior framing/ sheathing surfaces can cause similar issues by trapping moisture in the framing cavity. A moisture barrier ( low perm primer ) can help at the interior surface of the walls and ceiling. If the lowest permeability factor is at the interior surface, then the framing cavity can stay dryer, in theory.
Glad that the build show is addressing the diference between the UK and US on spray foam insulation.
I live in London and most of our stock is Victorian then 1930 to 1970 stock. We have a very low new build rate.
we had you black mould creases in the 1980 with dry rot in new build timber homes. This lead to a reduction in timber framing in the UK. Most new houses are block and brick cavity construction.
on older properties, we did not have parking ( underlament to the US). As Matt points out we traditionally have on condition loft spaces.) No roof vents or poor loft ventilation. Moisture is Or was controlled by ventilation through the slate or tiled roofs. ( I am leaving out Thatched roof as that is outside of my practice area).
So spraying foam between the rafter is not desirable. As it creates condensation.
When roofs are recovered a marking is normally added. But is normally a bitumas membrane type. It not common to use a smart breathable membrane at this point.
There is also a tendency to use the foam on roofs that have reached the end of there lifes. Which is not appropriate. Hence banks and insurers .
Good on you Matt for doing a deeper dive on the story. One of the ills that has grown out of the digital landscape is a tendency to take in a headline and little else. Throw in the obligatory shock factor built in to the headline to encourage clicks, and it makes the "drive-by takeaway" that much worse.
Please dont use Chat GPT as a source, it is consistently wrong.
Chatgpt can be very accurate if you ask it questions the right way. The best way I have seen it explained is talk to it like you are walking up to a random person that knows everything to ask them a question. If you give some vague question it will get confused. If you give it a very detailed question it will be accurate. I also never do what is called zero shot prompting where I try to get an answer immediately. I'll tell it what I'm trying to accomplish and get it to first explain the process it should take to get an answer and I'll usually also give it a role to play. Once it gives me that information I'll tell it to start to work through the problem. Especially with the new models they have it will spend a lot of time working through the problem. The funniest thing I did was I figured out a bunch of different "experts" that would provide good input and once each of them gave me an answer I asked them to have a meeting. It took a while to get the answer but the output was funny because it literally was a meeting where they ended up having meeting minutes and I could see them actually debating each other and correcting any issues they had missed. The output was 61 pages long.
@hotshot619 Yes, thank you for saying something. It drives me crazy the way people have come to just reflexively trust the Elaborate Lie Machine. It's designed to spit out sequences of words based on probability--it's not an actual, thinking researcher that can understand what it's saying.
I agree in the sentence that cgdp is a bad source of info , better search for info and go to
Links that is presented and sheck the quality of that info .
Whether stats in the uk : go to there whether afforety.
You're incorrect, chat gpt has an accuracy rate of 99.3 %
Source, chat gpt.
I love that we are complaining about short form content not having all the details and then we use chat gpt as part of our research into the topic. The irony is clearly lost.
Most of the problems you described seem to be common practice once you get off the high-end of your foam insulation packages and go down to the cheap house builds and the people that do that they do all the bad things you're talking about. So I can definitely see these problems coming here to the US.
Ventilated antics are tried and true. Much more forgiving than unventilated antics.
Sure, just ignore the squirrels running around and pooping everywhere, and ignore freezing your ass off in winter or paying $400/mo in summer to air condition the place. Ventilated attics are OUTDOOR SPACES.
Nah. I sprayed my roof deck 20 years ago. My attic looks beautiful to this day.
@@Crusader1815if you do insulated rafters with narrow outdoor venitilated slits under the roof boards ( like 2") you can have full room height, and get a nice" non boxlike" room volume.
I have no idea how I landed in this video but it was fascinating and you explained it very well even to someone that knows nothing about insulation.
Before I watch the rest (I'm only 2 seconds into the interview), Im going to veture a guess that (like everything else HVAC related in GB) they are doing it wrong; Government subsidies caused a bunch of businesses to spring up overnight without proper understanding, training or expertise and a whole lot of salesmanship (backed by government messaging).
Now back to it, let's t see how my prediction holds up.
I concur. We had our city mandate on homeowners to put water pressure regulator. They said that if we do it within two months, we can get reimbursement, but if we don't, later on we will have to foot the bill. They even gave us suggestions which companies to call. After install, it needed to be inspected by the city inspector. I called and guy was send to our house in 2 days. I checked during those days about total cost and the highest price for top tier back then was $95. City stated that they will reimburse up to $850. Notice word "up to". The guy came, did it in 15min and charged us .... yes you guessed it, $850. Then magically city Inspector for which the wait time is usually over a month, showed up 2 hrs after job was done. We both went into crawl space and thank God he came so fast (although I found out later that they scratching each other's backs). The water was dripping and since we always had bucket sitting under crawlspace water shut off valve, I had already about 1 /4 of gallon of water in a bucket. I panicked and told the Inspector that I will call the guy to get his butt back right away to fix the leaking issue and a da... Inspector tells me " don't bother him, it will be ok. In time the dirt and and grease from the surrounding area will plug up the connection and act as seal and stop the leak. I know that guy and he is always doing a great job". That's when my red flag went up. The city inspectors and other officials were directing people to their buddies because there was "free" money flying around. I told his that I don't give a crap since I paid $850 for job that took 15 min and part for $95 (they probably had further discount) and based on travel cost of the company and per Hr labor, should cost on high end even if charging 1 hr labor, no more than $550. I called the guy back. He came back ticked off. This time I watched him like a hawk and it took him less then 7 min to fix it and no leak after that. I was furious because this city reimbursement money didn't come off the tree, it came for property taxes from all of us. People who couldn't afford to pay upfront costs and be home magically waiting during the week day hour for installer, got screwed.
I thought US government also provides tax subsidies for insulating homes.
From the UK here, you are 100% correct. Companies springing up and taking the Government money and doing an awful job and the homeowners then have to live with the consequences. Same thing is happening here now with Heat Pumps. Company’s springing up, taking government money and doing terrible jobs leaving the homeowners living with something costing them 4x the running cost of the perfectly serviceable natural gas boiler they had ripped out in the name of being green!
@@gund89123 It does, but it's for insulation in the general sense, not specific to foam.
Also, these are established industries in the states, with experience and established best practices. This is not to say that there are not shady installers making a mess of things in the states, there are, but it's not an entire sector that has just sprung up out of nowhere based on artificial incentives and promotional messaging (advertising) from government.
Great analysis, speaking from the UK. We have a history of government-incentivised unsuitable home improvement initiatives that later have to be undone. Also see cavity wall insulation and external wall insulation for examples.
Cavity wall insulation is 99% a good thing. There are a few examples of disasters, but millions of homes have been done with few problems. EWI is even more of a good thing because you have to really screw it up to cause problems. Mostly that comes from doing it on the cheap and using siliconed-on capping rather than extending rooflines, which of course practically guarantees a leak down the back eventually.
You are quite right that some of the shoddiest schemes have been done under grant-funding, and we've had far too many badly-done stop-start grant schemes. That doesn't mean that govt money to improve the housing stock is a bad things, nor does it mean that cavity wall insulation and EWI are bad things. We actually need dramatically higher rates of retrofit for buildings, and the more of them that are EWI-based the better IMHO. It's usually the best technically and lowest-risk major insulation intervention. But like everything in building, the detailing and design have to be right.
I worked in a building supply center in the Canadian prairies (think very cold) in the late 70's. The government had a program of rebates for increasing the insulation in your home. In addition to the standard fiberglass and styrofoam insulation people were using blown in insulation. The blown fiberglass insulation in the attics to increase the R value worked decently well. However in the walls there were two other types of blown insulation. The first was urea formaldehyde foam insulation (UFI) which was later banned in Canada. The fumes would literally poison the home. The only solution was to tear the walls out and scrape the insulation out. Needless to say these houses couldn't sell or get mortgages. The second type was cellulose insulation which was basically very finely ground up newspaper or wood pulp treated with a fire retardant. It work quite well. However over time the fire retardant would leach out (although the manufacturers say they have improved the process). Currently one manufacturer says the life expectancy of the insulation is 20-30 years (compared to fibreglass at 80-100 years). Another type of insulation for attics was vermiculite (Zonelite). This was a natural product that was later found in many cases (but certainly not all) to be contaminated with asbestos. Not good. Do your research and remember that sometimes the latest and greatest innovation isn't always the best.
Insulation in the UK is generally very poor to non-existent in many houses, and I don't mean to stereotype, but most people's solution is to just put on a sweater and drink a hot cup of tea.
I ought to be outraged by that comment … if I wasn’t sat here in a jumper with a brew whilst reading it. 😂
@@mattundercoat it is what i grew up with 😆the attic at my parents place had about 2 inches of glass wool insulation which was dong absolutely nothing. Quick trip to b&q and now they have 10 inches, and you could feel the difference immediately
Great video Matt. I was wondering about this.
I stopped watching Matt years ago when he said you want your house like a Yeti cooler. I cant even watch him now, I only came for the comments. My best guess is this dude will have a class action lawsuit by all the homeowners he's built for with his foam crap.
The predominant feature of UK climate (not that we have 'climate', we have weather) is the damp.
Relatively high cold temperatures feel bitterly cold due to the humidity.
We have a saying : too cold to snow. This comes from the times it gets really cold is when there aren't any clouds.
Matt may I suggest you reach out to Roger of the Skill Builder channel to understand how most UK houses are built
To quote Matt at 13:40 "...when an invariable leak possibly happens..." Exactly! Roofs WILL leak -- period! I've always felt that spray foam has no place in the rafters of a roof.
My reference was to older houses from the UK. You make a valid point though.
Matt, Robin Clevett is the one to meet.
Agreed
One huge error in your equation at around 8:00 is that the RH in the UK is way higher than you assumed. I just spent a year there and the average RH is around 60% there throughout the year (exterior during the winter is around 80% average, interior is in the 50-60% and yes they deal with tons of mold there), which makes the issue being talked about significantly worse.