German Architect/Construction Engineer/Prefab Construction Contractor here. Your videos are very informative about the US construction scene. But surely we wouldn’t ever do, what u guys are praising here. I advice anybody to check out the Eurocode Building Code on theese issues (available in Eng!). They are mostly created by German universities and Institutes, so they are pretty sound. For example interior insulation is something, everybody try’s to avoid for good reasons. U have literally no active Thermal mass and u will always have a dependency on artificial ventilation/dehydration methods, since there will always be a humidity problem as well. Also nobody is using oil based Foaminsulations in the interiors, for health reasons (except for slabs without possible connection to the air). IF u realy need to have a interior insulation, you always go here for a mineral based insulation like foamglass, which can be plastered with lime-cement plaster (natural desinfection of the wallsurface) and is beeing able to „breath“ humidity in‘n‘out to a certain degree. But if u build new, always try to avoid this stuff by using perimeter insulation on the outside of the basement, incl. a drainage plate and geotextile against the refill.
I'm building a new house now. We just finished the foundation. My wife's uncle is doing the site work and he's pushing hard for me to insulate under the slab before we pour in 2 weeks. I've been fighting against it thinking its a waste of a few thousand dollars. This video has me re-thinking my position.
I’m a spray foam contractor in Canada and we usually spray foam on top of the grave with closed cell foam it acts as the vapour barrier as well as the insulating factor. The big benefit of spray foaming rather than using insulation board is if there’s any voids it fills them in rather than spanning over
@@zzzzzzzzzzzzzzzz8635 think about it your right.the company's get the spray foam in large quantities at a discount then stiff the customers because they can.
What happens when the foam starts to degrade????? I don't get it, a foundation should last 150 years at least, that foam is good for 15-20 years... then what. Your foundation will either be floating and weak or completely collapsed... no?
Good building practice in Finland is to insulate the basement from the outside. We don't have many basements nowadays because it's cheaper to insulate the perimeter of the house with EPS or XPS rather than to build the basement below the frost line. Also post WW2 basements had inadequate drainage so there were a lot of issues with flooding so basements have bad reputation.
this. plus... doing a building with eps around the peremiter now. it's like -10*C for a month now... was sprayed -5*C. no heating what so ever, and it's been a constant 5*C inside. i imagine if it was underslab insulation, none of that free geo thermal heat would come through and it would be -10*C inside right now.
About to start work on a basement remodel in mixed humid climate. 50s house no slab insulation. Laying down deltaFL taped air tight - 3/4 iso foam - cement board. Steel studs 1” from wall, 2” closed cell up over band joist. Watching this - sounds like we’re pretty close. Matt and Steve, thank you.
Just a few comments from living north of 50 degrees latitude: (I'm not really an expert, so please feel free to disagree.) Bat insulation doesn't perform as well in basements as above ground, because the difference in temperature at the top and bottom of the foundation causes vertical air movement within the bat. In the dozen or so basements I've torn up, there are always some spots that have been continuously wet, even with proper vapour barrier & moisture seals, drainage, etc. Any kind of hollow wall construction in an exterior basement wall in a bathroom will cause problems. I prefer to attach foam board insulation directly to the foundation wall and drywall to the foam for these. I've only seen sub-slab insulation when there is in-floor heating, with the exception of one house about five hours north of Toronto that had full-height south windows that heated the slab in the winter.
From what i have seen and heard it is best to not have the foam directly to the concrete. They make a special drain mat you are supposed to attach to the wall behind the foam to allow the concrete to breath. The same style drain mat is attached to the outside of the foundation to direct moisture to the drain tile at the footings.
That "interior weeping tile" solution is designed for basement walls that still have some water leakage from outside. In such situations it is better to permanently fix the water infiltration problem on the outside of the wall. When you can't dig up the outside on a cost effective basis, e.g. due to a shared driveway with a nearby neighbor, then the interior weeping system can be used with a connection to a sump pump pit.
@@paulsp6371 I have done a lot of remodeling on houses that have open cell and closed-cell they have been holding water and rotting box plates sill plates top plates and is a climate for post beetles and termites what's on paper is one thing what's going on in the field is completely 100% true Owens Corning opening letterhead stated they will not get involved with spray Foams because they feel that it's the next asbestos material and we don't have enough technology to understand it at this point
@@gaylehiner9511 I could not find that letter. Do you have a link? I have seen another video where the foam needed to be removed/replaced due to poor application and serious air quality issues. Risky when you see some of the people that are installing this stuff. Not all are quality people.
Biggest mistake I made in my new house was not insulating under the slab! The tile floors in the bathrooms are uncomfortable in the winter due to cold radiating through the slab. Floor temps get down in the low 60's which makes the heat have to run more often. Great video!
@@stevenbaczekarchitect9431 LOL! I'm into Monolithic Domes and there the concrete is exposed on the inside. Why? Because of 3" of polyurethane insulation on the outside. It's like eating a Goose Down jacket to keep you warm... No, you put the insulation on the OUTSIDE.
dig out the perimeter of the slab, and slap some EPS boards around it. it'll do a good enough job, because soil is insulative and a thermal mass. you have infinite insulation on the bottom; it all escapes SIDE WAYS. the further down you run the eps boards, the more insulative it will be. varies a bit of course. say your soil is sand; sand has a r value of 7 per foot. run the EPS 4 feet in the ground, and the heat will have to go through R28 on the way down, and then another R28 on the way up to leak out to the surface.
This guy Steve, along with you Matt are absolute Geniuses when it comes to building super efficient, strong and safe homes ! I live in Ct and used to do insulation from the age of 18-27, and what a huge difference from then to now. This technique is beyond interesting and valuable and the way this house is being done should be a benchmark for all builders, thanks for showing and if you have anymore videos of this place, please show them. Thank you.
Thank you for insulating houses and basements and putting unfaced insulation in and covering with plastic it will keep my business going forever due to all the mold build-up you builders keep doing her and I'll just keep making my millions thanks
Awesome educational material, here given by two guys who are "national treasures" in my opinion. So no disrespect intended by my following comments. I am deeply grateful for EVERYTHING you do, and publish, so the rest of us can WATCH and LEARN. Especially, thank you for the warning of the "iceberg" moment that will wreak havoc if layering of building materials is mindlessly wrong! Meanwhile: 1) There is no mention of how deeply placed, below grade, this basement lies. 2) There is no quantification of the hydrostatic pressure exerted upon anything. 3) Is this on hilly, or flat, terrain? I've seen another of Steve+Matt videos, shot in Texas, where the surrounding land was shown, while a huge ground-water remediation project was poured. Egad that was awesome and mindboggling, to see that such countermeasures even exist. So many people (here in SoCal) just ignore geological issues. Not to mention all the SF-Bay people who live atop a powder keg... the San Andreas Fault. 4) I love the 10 inches of gravel, and the mention of French drains etc., in other words, this is a comprehensive solution; but: 5) If that gravel ever gets silted up, by any means over the next century or two, then really nasty things are gonna happen; so 6) Anyone who believes in, or uses, dry-well-type methods of sub-foundation water removal must contemplate the importance of all those air gaps between the gravel pieces. The gravel might hold up the building, but it's those air gaps that fill with water and allow an underground river to flow. Thank you for considering my comments.
keep in mind, a closed cell insulation, below grade, on an exterior wall is illegal in the Midwest which is why it is also illegal to use a vapor barrier or in some cases, not even faced insulation under those circumstances. The moisture needs to be able to evaporate vs. being trapped.
Yep, that wall has 2 sides, and there is no way to guarantee that they can keep moisture out of the concrete wall, thus it has to be able to dry to the inside.
I wondered about this...check some of the articles Building Science Corp and Fine Homebuilding about why this works. According to Joe Lstibirek, PhD, 3.5” of closed cell still has enough vapor transmission to allow it to dry to the inside. Anything over that could be an issue.
@@Shad0wC0mpany2 That's because I believe in airtightness, water management, and surface temps of condensing surfaces - with that vapor doesn't scare me at all
Great video!! I have designed basement slab insulation systems and never stopped to consider WHY we put the poly on top of the EPS. Makes total sense! Just say no to "iceberging"!
@@rotaxrider in my area (central canada) I have never seen a code showing specific order... I typically do poly on top for this exact reason... Building inspectors never question it.. they just want to see proof of foam thickness if the plans called for a specific thickness..
I'm planning to (owner) build a home in northern NH next year and want to achieve a very high efficiency level. All these videos are going to serve me well. Very much appreciated.
Daniel, tread lightly. Demand MSDS sheets on all foams you consider. Most off gas, killing anyone inside during a fire. Many breaks down from the elements and time, eventually turning to dust. Some shrink as much as 36%. Others detach when sprayed on concrete. In short, if any of these problems concern you, it's best you get it in writing. If they can't show you an "aging test" or off-gassing test or shrinkage test or loss of R-value test, then assume they can't pass one.
@@larrymaloney877 Thank you for that tip, that makes complete sense. I'm guessing that extreme temperature changes like we have, would only worsen those issues. I'm also very suspicious of the tapes being used to seal exterior sheathing/foam. Unless it's chemically bonding with the substrate, I don't see how that could last a century or more.
I worked making fresh salsa for several years. We ran our production line at sixty degrees and operated out of an old freezer warehouse. We chose the building exactly for that reason. The floor and related substructures were probably a little over four feet thick. Concrete, foam and stone, then another series of concrete, foam and stone. Pretty impressive construction.
My personal notes: 1: can rebar Concrete foundation walls be poured with the below grade rebar basement foundation slab as a monolithic pour to prevent air gaps? 2: for my 2x8 wall frame beams, I must learn from this video by distancing them a few inches from the concrete wall so I can pour closed cell foam exact same way as is taught to me here in this video. 3: Why does he say the walls aren’t structural? Are the concrete walls the only structural component? 4: Steve also like me thinks it’s a good idea to have a hydro break aka he pours 10 inches of leveled stone with a perimeter drain running around the foundation so that water never is in constant contact with the foundation like most houses. 5: Above the stone but under the concrete he has 4 inches of a special Type 9 EPS styrofoam that is rated for at least 25 PSI so it won’t break when the concrete above it is poured.
Insulation outside the slab is best, as the thermal mass remains inside the home. It’s why my 3600sqft brick Victorian only need 4 tons of in SE Iowa cooling despite tons of windows and no insulation. It just changes temperature too slowly. Most AC runtime is shifted to nighttime as the brick remains warms for hours. In the hottest part of the day the brick is still warming up.
Fascinating ! Did I get this right?? 8-10" rock A french drain around the floor edge 4" foam//25 psi rated 10mm moisture barrier 4" concrete pour How deep is the basement?? 10-12'? What about plumbing/sewer? Thanks Matt !!
I'm just doing my basement walls. spray foam was going to be about $7000.00. I put R28 batt insulation in for $1200.00. I did get the rim joists sprayed for $1700.00 so it cost me $2900 instead of $8700. The house walls are R24 and the ceilings are R55. We have triple pane windows too. I put rigid foam under the concrete floor which has heating pipes in it. It would have been good to sprayfoam but $5800 will buy a bunch of heat. Sometimes you have to do what you can afford.
I’ve got 2-3 feet of stone with tile in it , Polly and 6” of concrete on top . My coal stove is in the basement and yes it takes a day or two to heat everything up but one the concrete is warm everything evens out . In the summertime you put a box fan on the floor and it blows across that concrete - your gonna freeze ! Blankets in August !
You can insulate after. Insulating pumped screeds are available now. I wouldn't bother personally though. It's much better to pour concrete on grade than foam that will creeep.
I love the budgets Steve has to work with, my clients don't have the $'s for these luxuries also the loss of space would be problem for many referring to the shots of the double framed. I do love all he does, I just wish my customers had the money.
Todd, it is always a challenge to get clients to see the value. Most of them are not knowledgable. It is our job to make them see the light, and I know this, they ALWAYS have the money
Steve... they don’t always have the money. Not unless they are building custom with a finance of $850,000 CAD or more. To add all that extra care & work would be about $20,000 where I live (on a large home). On a large addition say 18’x40’ it would be about half that just to start. Basically building costs about $100-250/sq. ft. And that $100/square is for traditional framing meeting code with cheap Home Depot cupboards.
Also see the Insuladd interior paint additive. A guy using it inside a boat told me about it, to take up less space for existing construction. It is made from ceramic beads, a byproduct from burning coal.
Matt, I've got to say....I love these northern climate segments! This video was too short! This is some great info on basements and slabs. The only thing I would add is that XPS is a far superior under slab insulation. While his capillary break of 8-10" of free draining stone should keep water away from the foam, the vapor barrier is above the EPS (which I agree is better to prevent "iceberg " affect). The under slab insulation will still be exposed to moisture from the ground that migrates up and will degrade to R value over time. XPS will also hold up better over the life of the slab. I would also add that XPS should be used UNDER the footings and up the sides to meet the slab insulation....it all in the details! I thoroughly enjoyed this segment. Thx!
Sonny Lloyd - yes it would be allowed. Very good undisturbed soils are at most 3000 psf, with an average assumed compaction of 2500 psf for residential. XPS foam has a minimum compressive strength of 5000 psf and can exceed 12,000 psf. So XPS foam easily exceeds the soil compressive strength a footing would bear on. An example is a bridge project on I-5 only 10 minutes from my house where they are using EPS foam to build up 40' of depth for the road bed instead of using compacted structural fill.
understood. but i literally just tried this two months ago with a "frost protected shallow foundation" and inspector didn't allow it. maybe if i had tried your argument and provided some test data from XPS manufacturer i would have had better luck. for me in Canada, under the slab yes, under the footing no.
Micah, EPS foam has a faster wet to dry value than Xps foam, the gravel and venting provide a drying action under the slab, also long term Xps foam releases their blowing agents for ever while shrinking in size. Steve designed a residence based on a styrofoam ice chest which holds your beer cold or chicken wings hot just don't put them in the same chest or you have oven ice cubes.
Being a remodel of a basement, the closed cell foam makes sense. However, if this was new construction why wouldn't the goal be to apply the insulation to the exterior prior to backfill? This complements the use of insulation under the slab. I plan to use a rockwool product because it also deters termites and does not degrade in the presence of moisture.
Matt, I don't have a basement, and I'm sure as heck not a construction expert, but these are just so informative that I can't help but watch you ONnn the BUILD SHOW :D
Lots of good ideas here. We vary somewhat from what's done here. Poly isn't used because it has permeability. Stego or Husky as vapor barrier has zero perm. When a slab is already in place we use Radon seal for water, radon, eveything protection. No vapor of any kind gets thru. Then, after that with an existing slab we would put 2" of continuous closed cell foam as a thermal break and double layers of 1/2" plywood in opposite directions top of that. This assembly looses 3"
Keep these northern climate videos coming! I love what you do, but I have been dying for some videos that pertain to the "other half" of the country. I think you will really expand your audience.
The one issue with the slab assembly is bringing that vapour barrier up 18" above the floor slab and then spray foaming over that. Closed cell spray foam can't adhere to the vapour. it will actually start to separate and case breaks within your spray foam (which is now the walls vapour barrier). also remember to specify type of spray foam to be 2lb polyurethane spray foam - anything else (0.5 and 1.5lb) are open cell products so there's a higher risk of condensation forming on the assembly (which is why it's also not code compliant in Canada). using rockwool insulation, and continuing the vapour barrier from the slab (with gasket below the parition sill plate), is another effective way to go. just a pain to seal around the joists. great video!
Question on under slab insulation! Where there is a column that is carrying load to a footing, is foam usually capable of carrying through that load from the column to the footing? Appreciate all that you guys do!
Tell me about the cross section of 2x material under the floor joists above. Where I live, most contractors insulate between the floor joists and drywall directly to the floor joists above (uusing blocking to stabilize the floor joists.). What is the benefit of the 2x lumber attached and running perpendicular to the floor joists I see in most of your videos? I live in NE Pennsylvania.
This concept is awesome, making that basement air tight. Out west here in Colorado and SD we have issues with Radon Gas, I would think this would negate the need for a radon gas removal system saving a ton of bucks.
Radon (and radon mitigation systems) is pretty common in Boston area. I'm sure the building the foundation this way is more expensive than radon mitigation. And radon seeping through the concrete so it would need to be installed anyway.
my slab currently is sitting between 72 and 75, i'm mid remodel and so some portions of my concrete walls are exposed on the inside that are above ground outside on the side that gets afternoon sun, here in the middle of the night that section of concrete is just shy of 79 and I can say for sure that concrete is not insulated on either side. current outside temps around 70, yesterdays high was 90-93 and ground temp for my area is around high 70's at 8 inch deep
interesting twist on closed vs open is if you have a cinder block foundation you should think about open cell. it will potentially allow the moisture to move which could save the block and mortar from deteriorating (assuming a retro fit old block foundation which may not be well sealed on the outside.
I'm confused about the closed cell on the basement walls. In the floor you have EPS then poly then the slab. Why not have EPS and poly on the outside of the walls to decouple the foundation walls from the earth outside, insulate the walls, and keep the moisture barrier on the outside of the walls instead of the inside. Aside from the thermal issues, it seems that hydraulic pressure from moisture coming through the foundation walls is eventually going to push the closed cell away from the walls, and pool water between the walls and the foam. Looks like the right idea in the floor, but backwards in the walls.
Patrick It's a terrible construction, but the US can't build concrete housings. Look how it's done in Germany, they know how to build massive. Never use sprayed PU foam on the inside. It contains harmful substances. Keep the concrete on the inside, it will hold the temperature and moisture constant for good room climate.
My guess is the outside foundation walls were also waterproofed. The issue with eps on outside is in cool climates the earth expands and contracts and eventually will destroy the foam. This is why it is now required in many areas to have a 6 mil Poly between earth and eps to act as a slip but this never works in reality. The technique they are using is a very good and cost effective solution if building this way. I only build with icf which solves all these issues with ease
@@paulnovak833 How is the foam exterior of an ICF block any more resistant to those foam-destroying forces than sheetfoam or sprayfoam applied to a block or form-poured basement wall?
Alaska requires special foundation insulation detailing so you don't melt your permafrost subgrade. Everywhere else, the basement slab is a nice cool element in the summer and should only need insulation when close to an exterior face (at 2 ft from an exterior face the soil itself will give you an R-value of 12 to 24).
Was hoping ,based on the title this was a renovation. Would be a lot of jack hammering to insulate the floor this way in an existing home unless you had a huge ceiling height and could just cover over the existing. Love Steve both in these videos and in person!
How do you know where the moisture is condensing in between the closed-cell foam and the foundation wall? Seems like trapping moisture in there might cause degradation of the foundation wall over time.
Mr. Rissinger, I am not a builder, I have been thoroughly geeking out on your channel for the last 6 months trying to absorb everything you share with modern building science. I am curious, since the walls are poured before the slab, how do you moisture/thermal-insulate the foundation walls at the bottom and exterior so they aren't a heat loss/moisture-wick?
You can wrap the whole foundation in XPS, They should have insulated the exterior, but for some reason they wanted to spend the extra money and time for a less temp stable room...
Steve doesn't like the Outro? Come on that is the best part! I am getting ready to install insulation before my slab goes down. Doing that same technique.
My only thought here is that there needs to be some planning for how much vertical space that slab system takes up. If you really want your 8 or 9 foot ceiling then you'd have to account for (conservatively) the 20-22 inches of space used up by a system like that. Really solid and good, but make sure the rest of the foundation is poured low enough to account for this loss of space.
our hydronic system rests on top of 3 inches of yellow closed cell foam board. Pex is stabled to the foam board. Perimeter foundation has 3 inches yellow foam board insulating 3 feet below grade. Our slab floats within the perimeter of the foundation walls. Has not cost us over $600 per heating season so far.
It's better to have the thermal mass (concrete, blocks, wood, metal) on the inside of the insulation, not on the outside. This helps smoothing out the internal temperature and keeps the structural materials from being exposed to temperature changes. As it also puts it behind the moisture/vapor barrier it's also protected from water and other things like radiation (on which side of the insulation your vapor barrier goes depends on your climate). Matt said it himself in one of his other videos about brick-veneer on the outside being a dumb idea. Same applies here. If you look at the Building Science Corporation website and search for 'the perfect wall', they will also give you the perfect slab and the perfect roof, which are nothing else than that very same perfect wall, just oriented horizontally - and the insulation is on the outside, every time.
Steve just said, it takes the condensation from the cement block and transfers it to the foam. What good is that? Roll out and attach Platon or DMX Air Gap on the walls and floors first! Then insulate. There won't be ANY condensation! TRUST ME... spray foaming directly on the concrete is NOT how to do it. With Platon installed, you could have a problem basement with an active moisture problem and it won't be an issue. Moisture can freely flow in the isolated space created by the dimpled Platon/DMX material. BONUS: It's extremely reasonable in cost and easy to install.
Love your channel, been watching for years! Our 1956 Minnesota rambler has 12" block and we will be insulating the walls with closed cell just like this. We had to install drain tile and a sump system around the entire foundation and the foam will act as a vapor and air barrier for radon and moist. However, I would never insulate under the slab in this climate since the "cold" floor is 50 to 70 degrees WARMER than the winter air outside. Makes it easier to heat the house in the winter and cool in the summer.
Great idea in the North. Foam of any kind in contact in the south is a nightmare. Over time termites will tunnel through the foam and leave the slab almost floating causing major cracks
Interesting, not sure I totally agree. I had a house in New England and purposely did not insulate the slab. I used ground as part of my heating system relying on that big thermal mass. My house was over 100 years old two story that I added insulation to , including the cellar walls. When my furnace stopped do to electrical outage the cellar never went below 55 , first floor was just below 50 and second floor 39, outside was below zero. Why was second so cold when heat rises? Well with 24 windows the controlling factor was the outside air . If I had insulated my slab I would broken that 55 degree natural ‘heat pump’. Just saying that you may want to think twice on this point. Then I’m a Boy Scout and a bit of a prepper with the need to ‘be prepared ‘ drilled into me. Another plus was that we moved family into the basement and with the people , candles and such working the cellar went up to the low to mid 60’s.
There are good and bad things to high thermal mass. If you are aren't actively heating the space it has the advantage as you say here. It will help keep the temperatures up significantly higher then the outside air. However, if you are actively heating that space it has a huge downside. While the ground temp might be 55F the thermal mass is gigantic so your interior ~75F heated air can transfer thermal energy to it practically indefinitely and the temperature will never rise because the thermal mass is so great. You are effectively pouring energy into the ground.
Unless you live in the most Northern climates (like Alaska) basements provide essential cooling in the summer. I'm thinking insulating the basement floor in the winter can be just as easily achieved (and probably more economically) by using a carpet with a thick foam pad.
If you want it for cooling basically using no energy in the summer, it would be better with no insulation. But if you want to stay warm and save energy you will basically freeze without the insulation. That concrete will never ever heat up unless you had a raging fire, even then, 10 feet away the concrete would be super cold because your actively fighting with the earth's natural temperature. The idea about thermal mass is, you want direct control of the "mass" temperature, so it will stay that temperature longer, without insualtion you have little to no control over the "mass". If you would have insulated your slab or not, it's still going to be 55 degrees regardless but the difference is how long it takes for it to change temperature.
Yes, it is a thermal mass. It's also a major source for heat to leave your structure. So you get the benefit of it staying warmer longer down there at the cost of increased heating at all other times. Congratulations? Thermal mass needs to be insulated from the external environment to be of any real benefit. That's why those underground homes you see have massive plastic sheets buried underground overtop of them. The soil is a thermal mass, and the sheet keeps the soil around the house dry. Dry soil is a good insulator. Wet soil, not so much.
once was looking to buy a home, and decided to determine what the house sat on. Slab? Basement? Nope. Now, I've also seen a "rubble" foundation, but no. What was the house sittting on? What kept it above the ground? River rocks! I could see, as they were redoing the kitchen floor. Shocking. The home sat on a handful of rocks, each the perfect size to skip across the lake. Coming into the home, you could see most of the home sat on a giant slab of shale. Looking under the kitchen plywood, you got a feeling the home predated plywood. I could find nothing to indicat that anything other then weight kept the home bolted down.
Many homes in New England have issues with radon. It's easily solved with a mitigation system that could have been installed in the basement and home walls before this project was wrapped up. it's basically just a vent tube with an air pump.
This is one of the best videos I have seen on basement insulation. Is a sump required with this setup or would it be redundant? How would a French drain be applicable?
Good idea, but I spray closed cell on the outside of the foundation, below grade, which will waterproof, insulate and proved space inside for more batts.
The slab looks like it's floating. It appears as if there is a small (one or two inch) gap between the gravel and the foam layer, with the concrete poured right on top of the foam. How is this? Or is it that the is foam resting right on top of the gravel and the gravel has been moved away slightly from underneath the foam in the cutout you used to show the layers? I can't figure out why it appears this way, and if there is any significance at all.
Check out above Matt at end of video the closed cell insulation is pulling/shrinking away from stud. This would be a major air leak. An issue I always think of where spray foam is applied and soon after gyproc covers the wall and there is over time the shrinking insulation that is allowing the air to enter building. Should a vapor barrier (plastic sealed wrap) be installed and tape sealed as an assurance against this type of incident?
I'm wondering which town outside of Boston. I build in central Mass and in the basement I need a fire break every 10ft to pass inspection. Usually either PT or Roxul. Also we usually have r18 minimum so would need another r3-4 not by choice. And sometimes when using closed cell we get forced to use 5/8 sheetrock or 1/2 blueboard and plaster also for fire. Thanks for visiting the area! 😊
Been wondering if this same slab detail could be used with no concrete and the 2 layers of Advantek instead. And instead of Type 9 EPS, to use something like Rockwool comfortboard 80 or 110. Although that EPS is probably going to be the most cost effective.
Very well done, I know with the stone, insulation and vapor barrier being under slab there is little chance of capillary wicking of water from slab/footer. My question is since you run the spray foam insulation up into the M joist do you fully cover the M joist or leave some exposed to the inside so that in case any water wicks up in can diffuse though the m joint into the basement so the m joist doesn't rot/mold?
I was wondering the same thing. If the M joist is fully sealed inside, but not insulated and sealed on the exterior, it will wick moisture and not dry during the northern fall-winter-spring.
I live in Southern Minnesota and think about foundations and slabs a lot. This video's slab insulation process looks more complicated than it needs to be, at least from my thinking. I've been thinking about a good six inches of sand that is leveled and compacted on top of packed earth. I would then lay down one inch of dense foam and pour my slab on top of that. It's just something I've been thinking about and I'm not sure it's a good idea. What about painting the outside of the poured walls with roofing tar and glue on one inch dense foam board before back-filling with gravel and sand, finished with clay and top soil.
Hy-Tech aluminized paint for concrete along with radiant barrier under the slab keeps my “unheated” basement 6degrees warmer in winter than the main floor, which has radiant heating. My basement is a rectangular pizza box
Are the walls not insulated on the outside? If they are, is the inside insulation needed or is it just giving you 'extra'? Wish my slab was done like this (or done in any competent way..). For our daylight basemetn foundation walls i used Insofast panels as we weren't going to spray foam and didn't want to use the space to foam panels and stud wall.
Matt, love the videos. Q: Is there a separate radon barrier that turns down at footing in addition to that 10 mil turning up the wall? Or does the CCF keep the gasses from infiltrating the basement?
From up north, too bad more builders don't insulate properly. Why not insulate on the outside of the basement concrete walls? Provides a thermal block and keeps the basement and main level floors way warmer...
Hey Matt, can you address any questions or issues people may have with their insulated slab cracking? Apparently many people doing this are having problems with their slab cracking all over. Any info would be great. Thanks.
The concrete cures too fast from the surface and shrinks faster than on the bottom. The plastic underneath the slab slows down the curing, since the water can evaporate only upwards from the concrete. Cover the surface with a tarp to slow down the curing.
The most common concern I had when I was in redi-mix was concrete being placed too wet. Contractors were known to ask for more water added on the job. While it makes it easier to work in the moment, the loss of cured strength and shrinkage cracks are high prices to pay. The above comment about the poly seal below requiring all of the moisture to migrate upwards bears true. Keeping the surface of concrete damp as it cures is never a bad idea.
I have an older home with cinder block walls that have seepage. I don't think this would be advised for someone in my situation. I had to break concrete and run internal drain tile and drill weep holes at the bottom of the block.
Here in utah there int any homes that have anything under the slabs other than 1/2-1" crushed rock, if a slab has hydronic heating then it'll have 2" of polystyrene but if it doesn't have the slab heating then it's just rock.
If you are building new and you intend the finish the basement. Why wouldn't you use insulated concrete forms? Basement insulation is installed as part of the wall forms with ICF.
In the South, would it be better to not insulate on the inside of the foundation wall to keep the thermal mass of the concrete wall within the conditioned space?
So what if you already have the slab down and want to insulate the floor? I did xps on the walls and framed on that. Next is batting and astic covering....but the floors?
I agree with other ppl icf is the way to go then you have a continuous vapour barrier and insulation. You dont lose any r value between the floor and the walls. Spray foam is a good alternative for retrofit applications.
I insulated my basement floor with 1" of XPS foam, 5/8" OSB on top secured with concrete screws. Works well and much, much cheaper than those insulated basement floor tiles. Losing an inch and 5/8 headroom is not that big of a deal.
Great video. What's the purpose of the square opening in the basement floor? And why is there a gap between the foam and the rock. Shouldn't the foam be resting on the gravel?
I have a house built in the 40's, grandfather used cinder block walls as the outer retaining walls in the basement, how would I go about sealing them from moisture and help against collapsing? They have started to crack and bow in. im in northern texas, we don;t get a lot of rain but the humidity is always high.
Skinny Mcdoogin , look into Rhino Carbon Fiber wall straightening system installed over hydraulic cement , this will make your foundation good as new. Then install InSoFast insulation great dyi product.
German Architect/Construction Engineer/Prefab Construction Contractor here. Your videos are very informative about the US construction scene. But surely we wouldn’t ever do, what u guys are praising here. I advice anybody to check out the Eurocode Building Code on theese issues (available in Eng!). They are mostly created by German universities and Institutes, so they are pretty sound.
For example interior insulation is something, everybody try’s to avoid for good reasons. U have literally no active Thermal mass and u will always have a dependency on artificial ventilation/dehydration methods, since there will always be a humidity problem as well. Also nobody is using oil based Foaminsulations in the interiors, for health reasons (except for slabs without possible connection to the air). IF u realy need to have a interior insulation, you always go here for a mineral based insulation like foamglass, which can be plastered with lime-cement plaster (natural desinfection of the wallsurface) and is beeing able to „breath“ humidity in‘n‘out to a certain degree.
But if u build new, always try to avoid this stuff by using perimeter insulation on the outside of the basement, incl. a drainage plate and geotextile against the refill.
I know you're from down south but I'm loving these segments about building strategies in the Northern climates, they really apply to me.
same here...
me too, minimum code is R-10 for basements here, and they've already beat it!
Ditto. So helpful!
I'm building a new house now. We just finished the foundation. My wife's uncle is doing the site work and he's pushing hard for me to insulate under the slab before we pour in 2 weeks. I've been fighting against it thinking its a waste of a few thousand dollars. This video has me re-thinking my position.
Always worth insulating
I’m a spray foam contractor in Canada and we usually spray foam on top of the grave with closed cell foam it acts as the vapour barrier as well as the insulating factor. The big benefit of spray foaming rather than using insulation board is if there’s any voids it fills them in rather than spanning over
But can't it get into the gravel and stop the movement of any water.
@@robertgregory2618 I would think it would only makes its way into the gravel by an inch or two before it sets up.
I can't imagine that you would ever recoup the additional cost in energy savings over board insulation.
@@zzzzzzzzzzzzzzzz8635 think about it your right.the company's get the spray foam in large quantities at a discount then stiff the customers because they can.
What happens when the foam starts to degrade????? I don't get it, a foundation should last 150 years at least, that foam is good for 15-20 years... then what. Your foundation will either be floating and weak or completely collapsed... no?
Good building practice in Finland is to insulate the basement from the outside. We don't have many basements nowadays because it's cheaper to insulate the perimeter of the house with EPS or XPS rather than to build the basement below the frost line. Also post WW2 basements had inadequate drainage so there were a lot of issues with flooding so basements have bad reputation.
What if you cannot insulate a cold celler from outside? Any possibility to insulate from inside without risks of mould or moisture?
@@vickzin If I had to insulate from the inside I would leave a vented gap between the wall and insulation.
this.
plus...
doing a building with eps around the peremiter now. it's like -10*C for a month now... was sprayed -5*C.
no heating what so ever, and it's been a constant 5*C inside.
i imagine if it was underslab insulation, none of that free geo thermal heat would come through and it would be -10*C inside right now.
About to start work on a basement remodel in mixed humid climate. 50s house no slab insulation. Laying down deltaFL taped air tight - 3/4 iso foam - cement board. Steel studs 1” from wall, 2” closed cell up over band joist. Watching this - sounds like we’re pretty close.
Matt and Steve, thank you.
I've never built anything more complicated than a dresser, no idea why I watch this but I enjoy it so much!
It's wild how Steve seems like he's not going to do well on camera until he starts talking and then is just awesome.
Its the sign of a guy who's in his environment, and knows his shit.
@@justinclark216right on. He is a professional
Just a few comments from living north of 50 degrees latitude: (I'm not really an expert, so please feel free to disagree.) Bat insulation doesn't perform as well in basements as above ground, because the difference in temperature at the top and bottom of the foundation causes vertical air movement within the bat. In the dozen or so basements I've torn up, there are always some spots that have been continuously wet, even with proper vapour barrier & moisture seals, drainage, etc. Any kind of hollow wall construction in an exterior basement wall in a bathroom will cause problems. I prefer to attach foam board insulation directly to the foundation wall and drywall to the foam for these. I've only seen sub-slab insulation when there is in-floor heating, with the exception of one house about five hours north of Toronto that had full-height south windows that heated the slab in the winter.
From what i have seen and heard it is best to not have the foam directly to the concrete. They make a special drain mat you are supposed to attach to the wall behind the foam to allow the concrete to breath. The same style drain mat is attached to the outside of the foundation to direct moisture to the drain tile at the footings.
That "interior weeping tile" solution is designed for basement walls that still have some water leakage from outside. In such situations it is better to permanently fix the water infiltration problem on the outside of the wall. When you can't dig up the outside on a cost effective basis, e.g. due to a shared driveway with a nearby neighbor, then the interior weeping system can be used with a connection to a sump pump pit.
@@paulsp6371 I have done a lot of remodeling on houses that have open cell and closed-cell they have been holding water and rotting box plates sill plates top plates and is a climate for post beetles and termites what's on paper is one thing what's going on in the field is completely 100% true Owens Corning opening letterhead stated they will not get involved with spray Foams because they feel that it's the next asbestos material and we don't have enough technology to understand it at this point
@@gaylehiner9511 I could not find that letter. Do you have a link? I have seen another video where the foam needed to be removed/replaced due to poor application and serious air quality issues. Risky when you see some of the people that are installing this stuff. Not all are quality people.
@@gaylehiner9511 The next "asbestos" is already here it is called "fiberglass"
Owens Corning makes foamboard...
Biggest mistake I made in my new house was not insulating under the slab! The tile floors in the bathrooms are uncomfortable in the winter due to cold radiating through the slab. Floor temps get down in the low 60's which makes the heat have to run more often. Great video!
Thank you sir, I agree, if only the knuckleheads above would listen to reason...
@@stevenbaczekarchitect9431 LOL!
I'm into Monolithic Domes and there the concrete is exposed on the inside. Why? Because of 3" of polyurethane insulation on the outside.
It's like eating a Goose Down jacket to keep you warm... No, you put the insulation on the OUTSIDE.
dig out the perimeter of the slab, and slap some EPS boards around it. it'll do a good enough job, because soil is insulative and a thermal mass. you have infinite insulation on the bottom; it all escapes SIDE WAYS.
the further down you run the eps boards, the more insulative it will be. varies a bit of course. say your soil is sand; sand has a r value of 7 per foot.
run the EPS 4 feet in the ground, and the heat will have to go through R28 on the way down, and then another R28 on the way up to leak out to the surface.
Steve seems to be a humble and very knowledgeable architect, thanks for sharing!
Extremely lol!!!
This guy Steve, along with you Matt are absolute Geniuses when it comes to building super efficient, strong and safe homes ! I live in Ct and used to do insulation from the age of 18-27, and what a huge difference from then to now. This technique is beyond interesting and valuable and the way this house is being done should be a benchmark for all builders, thanks for showing and if you have anymore videos of this place, please show them. Thank you.
Thank you for insulating houses and basements and putting unfaced insulation in and covering with plastic it will keep my business going forever due to all the mold build-up you builders keep doing her and I'll just keep making my millions thanks
Yup...i always groan when I see that in a home. So common.
This basement will not grow mold!!!
Awesome educational material, here given by two guys who are "national treasures" in my opinion. So no disrespect intended by my following comments. I am deeply grateful for EVERYTHING you do, and publish, so the rest of us can WATCH and LEARN. Especially, thank you for the warning of the "iceberg" moment that will wreak havoc if layering of building materials is mindlessly wrong! Meanwhile:
1) There is no mention of how deeply placed, below grade, this basement lies.
2) There is no quantification of the hydrostatic pressure exerted upon anything.
3) Is this on hilly, or flat, terrain? I've seen another of Steve+Matt videos, shot in Texas, where the surrounding land was shown, while a huge ground-water remediation project was poured. Egad that was awesome and mindboggling, to see that such countermeasures even exist. So many people (here in SoCal) just ignore geological issues. Not to mention all the SF-Bay people who live atop a powder keg... the San Andreas Fault.
4) I love the 10 inches of gravel, and the mention of French drains etc., in other words, this is a comprehensive solution; but:
5) If that gravel ever gets silted up, by any means over the next century or two, then really nasty things are gonna happen; so
6) Anyone who believes in, or uses, dry-well-type methods of sub-foundation water removal must contemplate the importance of all those air gaps between the gravel pieces. The gravel might hold up the building, but it's those air gaps that fill with water and allow an underground river to flow.
Thank you for considering my comments.
sot he house if fucked?
keep in mind, a closed cell insulation, below grade, on an exterior wall is illegal in the Midwest which is why it is also illegal to use a vapor barrier or in some cases, not even faced insulation under those circumstances. The moisture needs to be able to evaporate vs. being trapped.
Rob Fischer I noticed that they mentioned NOTHING about moisture barriers in this video...
Yep, that wall has 2 sides, and there is no way to guarantee that they can keep moisture out of the concrete wall, thus it has to be able to dry to the inside.
I wondered about this...check some of the articles Building Science Corp and Fine Homebuilding about why this works. According to Joe Lstibirek, PhD, 3.5” of closed cell still has enough vapor transmission to allow it to dry to the inside. Anything over that could be an issue.
Why is moisture in a concrete wall a bad thing? do you think it is going to rot?
@@Shad0wC0mpany2 That's because I believe in airtightness, water management, and surface temps of condensing surfaces - with that vapor doesn't scare me at all
Great video!! I have designed basement slab insulation systems and never stopped to consider WHY we put the poly on top of the EPS. Makes total sense! Just say no to "iceberging"!
So poly on top of insulation and not underneath?
Is this how code wants it?
@@rotaxrider in my area (central canada) I have never seen a code showing specific order... I typically do poly on top for this exact reason... Building inspectors never question it.. they just want to see proof of foam thickness if the plans called for a specific thickness..
I'm planning to (owner) build a home in northern NH next year and want to achieve a very high efficiency level. All these videos are going to serve me well. Very much appreciated.
Great!!
Daniel, tread lightly. Demand MSDS sheets on all foams you consider. Most off gas, killing anyone inside during a fire. Many breaks down from the elements and time, eventually turning to dust. Some shrink as much as 36%. Others detach when sprayed on concrete. In short, if any of these problems concern you, it's best you get it in writing. If they can't show you an "aging test" or off-gassing test or shrinkage test or loss of R-value test, then assume they can't pass one.
@@larrymaloney877 Thank you for that tip, that makes complete sense. I'm guessing that extreme temperature changes like we have, would only worsen those issues. I'm also very suspicious of the tapes being used to seal exterior sheathing/foam. Unless it's chemically bonding with the substrate, I don't see how that could last a century or more.
Matt you jsut get it man. Love your info and tutorials. Im a DYI'er and your info helps tremendously. .
I worked making fresh salsa for several years. We ran our production line at sixty degrees and operated out of an old freezer warehouse. We chose the building exactly for that reason. The floor and related substructures were probably a little over four feet thick. Concrete, foam and stone, then another series of concrete, foam and stone. Pretty impressive construction.
My personal notes:
1: can rebar Concrete foundation walls be poured with the below grade rebar basement foundation slab as a monolithic pour to prevent air gaps?
2: for my 2x8 wall frame beams, I must learn from this video by distancing them a few inches from the concrete wall so I can pour closed cell foam exact same way as is taught to me here in this video.
3: Why does he say the walls aren’t structural? Are the concrete walls the only structural component?
4: Steve also like me thinks it’s a good idea to have a hydro break aka he pours 10 inches of leveled stone with a perimeter drain running around the foundation so that water never is in constant contact with the foundation like most houses.
5: Above the stone but under the concrete he has 4 inches of a special Type 9 EPS styrofoam that is rated for at least 25 PSI so it won’t break when the concrete above it is poured.
Insulation outside the slab is best, as the thermal mass remains inside the home. It’s why my 3600sqft brick Victorian only need 4 tons of in SE Iowa cooling despite tons of windows and no insulation. It just changes temperature too slowly. Most AC runtime is shifted to nighttime as the brick remains warms for hours. In the hottest part of the day the brick is still warming up.
Save so many hours of extra labour and material if you use ICF walls!
Fascinating !
Did I get this right??
8-10" rock
A french drain around the floor edge
4" foam//25 psi rated
10mm moisture barrier
4" concrete pour
How deep is the basement?? 10-12'?
What about plumbing/sewer?
Thanks Matt !!
I'm just doing my basement walls. spray foam was going to be about $7000.00. I put R28 batt insulation in for $1200.00. I did get the rim joists sprayed for $1700.00 so it cost me $2900 instead of $8700. The house walls are R24 and the ceilings are R55. We have triple pane windows too. I put rigid foam under the concrete floor which has heating pipes in it. It would have been good to sprayfoam but $5800 will buy a bunch of heat. Sometimes you have to do what you can afford.
I’ve got 2-3 feet of stone with tile in it , Polly and 6” of concrete on top . My coal stove is in the basement and yes it takes a day or two to heat everything up but one the concrete is warm everything evens out . In the summertime you put a box fan on the floor and it blows across that concrete - your gonna freeze ! Blankets in August !
You can insulate after. Insulating pumped screeds are available now. I wouldn't bother personally though. It's much better to pour concrete on grade than foam that will creeep.
I love the budgets Steve has to work with, my clients don't have the $'s for these luxuries also the loss of space would be problem for many referring to the shots of the double framed. I do love all he does, I just wish my customers had the money.
Todd, it is always a challenge to get clients to see the value. Most of them are not knowledgable. It is our job to make them see the light, and I know this, they ALWAYS have the money
Steve... they don’t always have the money. Not unless they are building custom with a finance of $850,000 CAD or more. To add all that extra care & work would be about $20,000 where I live (on a large home).
On a large addition say 18’x40’ it would be about half that just to start. Basically building costs about $100-250/sq. ft.
And that $100/square is for traditional framing meeting code with cheap Home Depot cupboards.
Also see the Insuladd interior paint additive. A guy using it inside a boat told me about it, to take up less space for existing construction. It is made from ceramic beads, a byproduct from burning coal.
This was great, good to see more about cold climates and more about basements.
Matt, I've got to say....I love these northern climate segments! This video was too short! This is some great info on basements and slabs. The only thing I would add is that XPS is a far superior under slab insulation. While his capillary break of 8-10" of free draining stone should keep water away from the foam, the vapor barrier is above the EPS (which I agree is better to prevent "iceberg " affect). The under slab insulation will still be exposed to moisture from the ground that migrates up and will degrade to R value over time. XPS will also hold up better over the life of the slab. I would also add that XPS should be used UNDER the footings and up the sides to meet the slab insulation....it all in the details! I thoroughly enjoyed this segment. Thx!
in my area, insulation UNDER the footing would not be allowed because the footing has to bear on undisturbed.
Sonny Lloyd - yes it would be allowed. Very good undisturbed soils are at most 3000 psf, with an average assumed compaction of 2500 psf for residential. XPS foam has a minimum compressive strength of 5000 psf and can exceed 12,000 psf. So XPS foam easily exceeds the soil compressive strength a footing would bear on.
An example is a bridge project on I-5 only 10 minutes from my house where they are using EPS foam to build up 40' of depth for the road bed instead of using compacted structural fill.
understood. but i literally just tried this two months ago with a "frost protected shallow foundation" and inspector didn't allow it. maybe if i had tried your argument and provided some test data from XPS manufacturer i would have had better luck. for me in Canada, under the slab yes, under the footing no.
Micah, EPS foam has a faster wet to dry value than Xps foam, the gravel and venting provide a drying action under the slab, also long term Xps foam releases their blowing agents for ever while shrinking in size. Steve designed a residence based on a styrofoam ice chest which holds your beer cold or chicken wings hot just don't put them in the same chest or you have oven ice cubes.
Rock wool/Roxul better solution subslab - avoids outgassing, moisture damage, shrinkage
Being a remodel of a basement, the closed cell foam makes sense. However, if this was new construction why wouldn't the goal be to apply the insulation to the exterior prior to backfill? This complements the use of insulation under the slab. I plan to use a rockwool product because it also deters termites and does not degrade in the presence of moisture.
steve knows his shit. thanks Matt
Matt, I don't have a basement, and I'm sure as heck not a construction expert, but these are just so informative that I can't help but watch you ONnn the BUILD SHOW :D
Lots of good ideas here. We vary somewhat from what's done here. Poly isn't used because it has permeability. Stego or Husky as vapor barrier has zero perm. When a slab is already in place we use Radon seal for water, radon, eveything protection. No vapor of any kind gets thru. Then, after that with an existing slab we would put 2" of continuous closed cell foam as a thermal break and double layers of 1/2" plywood in opposite directions top of that. This assembly looses 3"
Radon is rare. I wouldn't get too worked up over it. I guess from a marketing standpoint it's handy though.
Keep these northern climate videos coming! I love what you do, but I have been dying for some videos that pertain to the "other half" of the country. I think you will really expand your audience.
The one issue with the slab assembly is bringing that vapour barrier up 18" above the floor slab and then spray foaming over that. Closed cell spray foam can't adhere to the vapour. it will actually start to separate and case breaks within your spray foam (which is now the walls vapour barrier). also remember to specify type of spray foam to be 2lb polyurethane spray foam - anything else (0.5 and 1.5lb) are open cell products so there's a higher risk of condensation forming on the assembly (which is why it's also not code compliant in Canada).
using rockwool insulation, and continuing the vapour barrier from the slab (with gasket below the parition sill plate), is another effective way to go. just a pain to seal around the joists.
great video!
Question on under slab insulation! Where there is a column that is carrying load to a footing, is foam usually capable of carrying through that load from the column to the footing? Appreciate all that you guys do!
Any columns go directly to a footing - structure before energy
Tell me about the cross section of 2x material under the floor joists above. Where I live, most contractors insulate between the floor joists and drywall directly to the floor joists above (uusing blocking to stabilize the floor joists.). What is the benefit of the 2x lumber attached and running perpendicular to the floor joists I see in most of your videos? I live in NE Pennsylvania.
Steve at the end made this my favorite episode!!!
Thank you!!!
This concept is awesome, making that basement air tight. Out west here in Colorado and SD we have issues with Radon Gas, I would think this would negate the need for a radon gas removal system saving a ton of bucks.
Radon (and radon mitigation systems) is pretty common in Boston area. I'm sure the building the foundation this way is more expensive than radon mitigation. And radon seeping through the concrete so it would need to be installed anyway.
my slab currently is sitting between 72 and 75, i'm mid remodel and so some portions of my concrete walls are exposed on the inside that are above ground outside on the side that gets afternoon sun, here in the middle of the night that section of concrete is just shy of 79 and I can say for sure that concrete is not insulated on either side. current outside temps around 70, yesterdays high was 90-93 and ground temp for my area is around high 70's at 8 inch deep
interesting twist on closed vs open is if you have a cinder block foundation you should think about open cell. it will potentially allow the moisture to move which could save the block and mortar from deteriorating (assuming a retro fit old block foundation which may not be well sealed on the outside.
One of the best builders.. homeowners lucky to have you on the project
I'm confused about the closed cell on the basement walls. In the floor you have EPS then poly then the slab. Why not have EPS and poly on the outside of the walls to decouple the foundation walls from the earth outside, insulate the walls, and keep the moisture barrier on the outside of the walls instead of the inside. Aside from the thermal issues, it seems that hydraulic pressure from moisture coming through the foundation walls is eventually going to push the closed cell away from the walls, and pool water between the walls and the foam. Looks like the right idea in the floor, but backwards in the walls.
Patrick It's a terrible construction, but the US can't build concrete housings. Look how it's done in Germany, they know how to build massive. Never use sprayed PU foam on the inside. It contains harmful substances. Keep the concrete on the inside, it will hold the temperature and moisture constant for good room climate.
I agree you have to keep the moisture out. With that design the concrete walls will be constantly damp.
My guess is the outside foundation walls were also waterproofed. The issue with eps on outside is in cool climates the earth expands and contracts and eventually will destroy the foam. This is why it is now required in many areas to have a 6 mil Poly between earth and eps to act as a slip but this never works in reality. The technique they are using is a very good and cost effective solution if building this way. I only build with icf which solves all these issues with ease
@@paulnovak833 How is the foam exterior of an ICF block any more resistant to those foam-destroying forces than sheetfoam or sprayfoam applied to a block or form-poured basement wall?
@James Bloom icf block isn't going to move, nor would spray foam fornthat matter
Alaska requires special foundation insulation detailing so you don't melt your permafrost subgrade. Everywhere else, the basement slab is a nice cool element in the summer and should only need insulation when close to an exterior face (at 2 ft from an exterior face the soil itself will give you an R-value of 12 to 24).
Was hoping ,based on the title this was a renovation. Would be a lot of jack hammering to insulate the floor this way in an existing home unless you had a huge ceiling height and could just cover over the existing. Love Steve both in these videos and in person!
How do you know where the moisture is condensing in between the closed-cell foam and the foundation wall? Seems like trapping moisture in there might cause degradation of the foundation wall over time.
Always seal the outside of your concrete walls from water penetrating down to drainage system and sleve drainage piping from sediment buildup.
@@Eger7law011 Doesn't answer the question
I'm a big fan of Steve! He seems to enjoy his job so much.
#lovewhatyoudo
Mr. Rissinger, I am not a builder, I have been thoroughly geeking out on your channel for the last 6 months trying to absorb everything you share with modern building science. I am curious, since the walls are poured before the slab, how do you moisture/thermal-insulate the foundation walls at the bottom and exterior so they aren't a heat loss/moisture-wick?
You can wrap the whole foundation in XPS, They should have insulated the exterior, but for some reason they wanted to spend the extra money and time for a less temp stable room...
SunRa l
What?
Josh Herzberger , Check out Matt's video on Icf waterproofing.
Steve doesn't like the Outro? Come on that is the best part! I am getting ready to install insulation before my slab goes down. Doing that same technique.
My only thought here is that there needs to be some planning for how much vertical space that slab system takes up. If you really want your 8 or 9 foot ceiling then you'd have to account for (conservatively) the 20-22 inches of space used up by a system like that. Really solid and good, but make sure the rest of the foundation is poured low enough to account for this loss of space.
our hydronic system rests on top of 3 inches of yellow closed cell foam board. Pex is stabled to the foam board. Perimeter foundation has 3 inches yellow foam board insulating 3 feet below grade. Our slab floats within the perimeter of the foundation walls. Has not cost us over $600 per heating season so far.
Curious if you wanted a cold cellar in the basement would you do this or would you not do the section of the cold cellar?
It's better to have the thermal mass (concrete, blocks, wood, metal) on the inside of the insulation, not on the outside. This helps smoothing out the internal temperature and keeps the structural materials from being exposed to temperature changes. As it also puts it behind the moisture/vapor barrier it's also protected from water and other things like radiation (on which side of the insulation your vapor barrier goes depends on your climate).
Matt said it himself in one of his other videos about brick-veneer on the outside being a dumb idea. Same applies here.
If you look at the Building Science Corporation website and search for 'the perfect wall', they will also give you the perfect slab and the perfect roof, which are nothing else than that very same perfect wall, just oriented horizontally - and the insulation is on the outside, every time.
So this kind of concrete block would be perfect to make basement or even exterior wall. th-cam.com/video/loNqPTQqdNQ/w-d-xo.html
People don't put brick-veneer on their buildings for thermal reasons.
@@seigeengine
I know.
I'm an engineer, form follows function for me ;-)
Steve just said, it takes the condensation from the cement block and transfers it to the foam. What good is that? Roll out and attach Platon or DMX Air Gap on the walls and floors first! Then insulate. There won't be ANY condensation! TRUST ME... spray foaming directly on the concrete is NOT how to do it. With Platon installed, you could have a problem basement with an active moisture problem and it won't be an issue. Moisture can freely flow in the isolated space created by the dimpled Platon/DMX material. BONUS: It's extremely reasonable in cost and easy to install.
Question... is the hole left open to serve an an access hatch to the drainage bed below the insulation and floor slab?
Tub trap
Love your channel, been watching for years! Our 1956 Minnesota rambler has 12" block and we will be insulating the walls with closed cell just like this. We had to install drain tile and a sump system around the entire foundation and the foam will act as a vapor and air barrier for radon and moist. However, I would never insulate under the slab in this climate since the "cold" floor is 50 to 70 degrees WARMER than the winter air outside. Makes it easier to heat the house in the winter and cool in the summer.
Consider insulating OUTside the foundation, That thermal mass can make a much more temp stable living space.
@@joe4324 Excavation is too costly.
Great idea in the North. Foam of any kind in contact in the south is a nightmare. Over time termites will tunnel through the foam and leave the slab almost floating causing major cracks
Nothing better than a audio book and good cans to drown out shop noise.
Matt, Can you comment on the concerns on off gassing of closed cell foam and is there anything that can be done to reduce this concern
Interesting, not sure I totally agree. I had a house in New England and purposely did not insulate the slab. I used ground as part of my heating system relying on that big thermal mass. My house was over 100 years old two story that I added insulation to , including the cellar walls. When my furnace stopped do to electrical outage the cellar never went below 55 , first floor was just below 50 and second floor 39, outside was below zero. Why was second so cold when heat rises? Well with 24 windows the controlling factor was the outside air . If I had insulated my slab I would broken that 55 degree natural ‘heat pump’. Just saying that you may want to think twice on this point. Then I’m a Boy Scout and a bit of a prepper with the need to ‘be prepared ‘ drilled into me.
Another plus was that we moved family into the basement and with the people , candles and such working the cellar went up to the low to mid 60’s.
There are good and bad things to high thermal mass. If you are aren't actively heating the space it has the advantage as you say here. It will help keep the temperatures up significantly higher then the outside air. However, if you are actively heating that space it has a huge downside. While the ground temp might be 55F the thermal mass is gigantic so your interior ~75F heated air can transfer thermal energy to it practically indefinitely and the temperature will never rise because the thermal mass is so great. You are effectively pouring energy into the ground.
What you pour into the ground in the winter you gain back in the summer. Ac will be working harder to cool the house in the summer.
Unless you live in the most Northern climates (like Alaska) basements provide essential cooling in the summer.
I'm thinking insulating the basement floor in the winter can be just as easily achieved (and probably more economically) by using a carpet with a thick foam pad.
If you want it for cooling basically using no energy in the summer, it would be better with no insulation. But if you want to stay warm and save energy you will basically freeze without the insulation. That concrete will never ever heat up unless you had a raging fire, even then, 10 feet away the concrete would be super cold because your actively fighting with the earth's natural temperature. The idea about thermal mass is, you want direct control of the "mass" temperature, so it will stay that temperature longer, without insualtion you have little to no control over the "mass". If you would have insulated your slab or not, it's still going to be 55 degrees regardless but the difference is how long it takes for it to change temperature.
Yes, it is a thermal mass. It's also a major source for heat to leave your structure. So you get the benefit of it staying warmer longer down there at the cost of increased heating at all other times. Congratulations?
Thermal mass needs to be insulated from the external environment to be of any real benefit. That's why those underground homes you see have massive plastic sheets buried underground overtop of them. The soil is a thermal mass, and the sheet keeps the soil around the house dry. Dry soil is a good insulator. Wet soil, not so much.
Any exterior foundation wall installation?
1:30. Some shelving to recover the lost space would be great.
Was the exterior basement wall insulated? That seems to me like the place to start.
Steve knows how to build!!!
Thank you
once was looking to buy a home, and decided to determine what the house sat on. Slab? Basement? Nope. Now, I've also seen a "rubble" foundation, but no. What was the house sittting on? What kept it above the ground? River rocks! I could see, as they were redoing the kitchen floor. Shocking. The home sat on a handful of rocks, each the perfect size to skip across the lake. Coming into the home, you could see most of the home sat on a giant slab of shale. Looking under the kitchen plywood, you got a feeling the home predated plywood. I could find nothing to indicat that anything other then weight kept the home bolted down.
The poly is also required for radon underslab control.
Mass Code requires piping installed under slab
What about off-gassing? Long term air quality studies?
I suspect that's in God's hands. ;-)
Many homes in New England have issues with radon. It's easily solved with a mitigation system that could have been installed in the basement and home walls before this project was wrapped up. it's basically just a vent tube with an air pump.
@@chrishuyler3580 Thanks. Good info
8:09 wow! Can't get enough of this.
he should smile more. GOOD SMILE.
This is one of the best videos I have seen on basement insulation. Is a sump required with this setup or would it be redundant? How would a French drain be applicable?
Good idea, but I spray closed cell on the outside of the foundation, below grade, which will waterproof, insulate and proved space inside for more batts.
good vid Matt, glad this wasn't another infomercial....stay real , stay unique ..
The slab looks like it's floating. It appears as if there is a small (one or two inch) gap between the gravel and the foam layer, with the concrete poured right on top of the foam. How is this? Or is it that the is foam resting right on top of the gravel and the gravel has been moved away slightly from underneath the foam in the cutout you used to show the layers? I can't figure out why it appears this way, and if there is any significance at all.
Check out above Matt at end of video the closed cell insulation is pulling/shrinking away from stud. This would be a major air leak. An issue I always think of where spray foam is applied and soon after gyproc covers the wall and there is over time the shrinking insulation that is allowing the air to enter building. Should a vapor barrier (plastic sealed wrap) be installed and tape sealed as an assurance against this type of incident?
How do you insulate the slab when you are using Superior Wall prefab basement walls?
I'm wondering which town outside of Boston. I build in central Mass and in the basement I need a fire break every 10ft to pass inspection. Usually either PT or Roxul. Also we usually have r18 minimum so would need another r3-4 not by choice. And sometimes when using closed cell we get forced to use 5/8 sheetrock or 1/2 blueboard and plaster also for fire. Thanks for visiting the area! 😊
This was down on the Cape, feel free to contact me thru my website if you'd like to chat more. I'm actually from Western MA
Been wondering if this same slab detail could be used with no concrete and the 2 layers of Advantek instead. And instead of Type 9 EPS, to use something like Rockwool comfortboard 80 or 110. Although that EPS is probably going to be the most cost effective.
Of course have done that detail a number of times
How are the horizontal poly seams sealed together below the concrete slab or are they just overlapping?
Very well done, I know with the stone, insulation and vapor barrier being under slab there is little chance of capillary wicking of water from slab/footer. My question is since you run the spray foam insulation up into the M joist do you fully cover the M joist or leave some exposed to the inside so that in case any water wicks up in can diffuse though the m joint into the basement so the m joist doesn't rot/mold?
I was wondering the same thing. If the M joist is fully sealed inside, but not insulated and sealed on the exterior, it will wick moisture and not dry during the northern fall-winter-spring.
Dries to the outside
I live in Southern Minnesota and think about foundations and slabs a lot. This video's slab insulation process looks more complicated than it needs to be, at least from my thinking. I've been thinking about a good six inches of sand that is leveled and compacted on top of packed earth. I would then lay down one inch of dense foam and pour my slab on top of that. It's just something I've been thinking about and I'm not sure it's a good idea. What about painting the outside of the poured walls with roofing tar and glue on one inch dense foam board before back-filling with gravel and sand, finished with clay and top soil.
007vsMagua the roofing tar will eat the foam. The sand will hold water and not have big enough gaps of air to dry under slab which is important.
Hy-Tech aluminized paint for concrete along with radiant barrier under the slab keeps my “unheated” basement 6degrees warmer in winter than the main floor, which has radiant heating.
My basement is a rectangular pizza box
Are the walls not insulated on the outside? If they are, is the inside insulation needed or is it just giving you 'extra'?
Wish my slab was done like this (or done in any competent way..). For our daylight basemetn foundation walls i used Insofast panels as we weren't going to spray foam and didn't want to use the space to foam panels and stud wall.
Matt, love the videos. Q: Is there a separate radon barrier that turns down at footing in addition to that 10 mil turning up the wall? Or does the CCF keep the gasses from infiltrating the basement?
From up north, too bad more builders don't insulate properly. Why not insulate on the outside of the basement concrete walls? Provides a thermal block and keeps the basement and main level floors way warmer...
Also, imagine all the extra SPACE you get to have! [1:30 > super space hog]
That’s where my 2” rigid insulation is on my basement!
I assume it is. Under the slab is insulated, so why wouldn't the walls be? This is just a mega house
What do you insulate the outside basement walls with?
Yeah its the vest way, but cost more. People just see the price tag unfortunately
Hey Matt, can you address any questions or issues people may have with their insulated slab cracking? Apparently many people doing this are having problems with their slab cracking all over. Any info would be great. Thanks.
The concrete cures too fast from the surface and shrinks faster than on the bottom. The plastic underneath the slab slows down the curing, since the water can evaporate only upwards from the concrete. Cover the surface with a tarp to slow down the curing.
The most common concern I had when I was in redi-mix was concrete being placed too wet. Contractors were known to ask for more water added on the job. While it makes it easier to work in the moment, the loss of cured strength and shrinkage cracks are high prices to pay. The above comment about the poly seal below requiring all of the moisture to migrate upwards bears true. Keeping the surface of concrete damp as it cures is never a bad idea.
@@jamesharder5643 so it would prob be prudent to wet cure a slab that is poured over foam and plastic?
I have an older home with cinder block walls that have seepage. I don't think this would be advised for someone in my situation. I had to break concrete and run internal drain tile and drill weep holes at the bottom of the block.
Cinder on grade or below?
@@konjiki240sx below grade.
Here in utah there int any homes that have anything under the slabs other than 1/2-1" crushed rock, if a slab has hydronic heating then it'll have 2" of polystyrene but if it doesn't have the slab heating then it's just rock.
Wow, that's some nice Detail! ...but curious about the foam Between the concrete layer? 2" slab, foam, 2" additional slab?
If you are building new and you intend the finish the basement. Why wouldn't you use insulated concrete forms? Basement insulation is installed as part of the wall forms with ICF.
In the South, would it be better to not insulate on the inside of the foundation wall to keep the thermal mass of the concrete wall within the conditioned space?
How flammable is that insulation? Is pulling the studs off the wall a fire blocking issue?
No the vertical height of a cavity is limited to 12'
In older New England houses with a rubble or stone foundation rather than poured concrete, spraying foam isn’t recommended. Is there another solution?
So what if you already have the slab down and want to insulate the floor? I did xps on the walls and framed on that. Next is batting and astic covering....but the floors?
38tech , Call InSoFast and glue down to slab, then install subfloor and finish floor. Fast dyi.
I agree with other ppl icf is the way to go then you have a continuous vapour barrier and insulation. You dont lose any r value between the floor and the walls. Spray foam is a good alternative for retrofit applications.
I insulated my basement floor with 1" of XPS foam, 5/8" OSB on top secured with concrete screws. Works well and much, much cheaper than those insulated basement floor tiles. Losing an inch and 5/8 headroom is not that big of a deal.
Yup..and XPS is a nice vapor barrier!
Great video. What's the purpose of the square opening in the basement floor? And why is there a gap between the foam and the rock. Shouldn't the foam be resting on the gravel?
Maybe a sump pump? Also, it probably is, it just doesn't look like it here.
To answer a question from below, the hole is either for a sump pump or a radon vent pipe. (sump pump to pump out excess water if needed)
I have a house built in the 40's, grandfather used cinder block walls as the outer retaining walls in the basement, how would I go about sealing them from moisture and help against collapsing? They have started to crack and bow in. im in northern texas, we don;t get a lot of rain but the humidity is always high.
Skinny Mcdoogin , look into Rhino Carbon Fiber wall straightening system installed over hydraulic cement , this will make your foundation good as new. Then install InSoFast insulation great dyi product.
Do you put the EPS on the footing as well or do you terminate it before the footing?
2" of the 4" rides atop the footing