Spray Foam Attic Floor or Rafters: Which is Best to Insulate? | Foam University
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- เผยแพร่เมื่อ 21 ม.ค. 2020
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Is it better to put spray foam insulation in your attic rafters or floor? Learn more about this topic on this episode of Foam University.
Are you in a reading mood? Learn more about whether to spray foam the attic floor or rafters:
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#atticinsulation #atticrafters #atticflat #sprayfoam #sprayfoaminsulation #foamuniversity #foamu #professoroffoam #retrofoamofmichigan
Came for the pro's and cons of spray foam for my attic, stayed for the sensual red velour jacket.
The video information is great, but the jacket is the real star.
Great content Eric. Appreciate you sharing.
Im glad you thought so!
For new construction the best time to spray the roof deck is before any gypsum-board has gone up. The foam tech can easily spay down to the eaves without the fear of leaving voids, and it's easy to verify the foam has been installed correctly. The roof deck requires more square feet than the attic "floor" but the time and effort per square foot will be lower with no gypsum-board in the way. On the other hand spraying to the attic "floor" requires the gypsum-board be installed on the ceiling, light fixtures and other ceiling-mounted devices be installed, plus the foam tech must then must crawl around and possibly bang the back of their head on the points of roofing nails if the shingles have been installed. Since this is later in the overall build, that's a possibility.
Have spray foam on the attic floor from new construction. One thing I should have done when electrical and plumbing was being installed in the attic was to have it run a foot or so ABOVE the foam so it is not encased and difficult to find or make changes. Building 2 new straw bale structures and will do this simple adjustment. As far as temperature comfort in our house we love it! Our exterior walls are straw bale construction so incredible insulation values from that. Our attic space is very large and tall. We have the radiant backed roof decking under our Spanish tile roof. I did not want to condition this extra attic space so I had the floor sprayed. My builder-son says I essentially live in an igloo cooler with my walls and ceiling cap. When I do put the a.c, on the ambient temperature is quickly reached and will maintain the desired temp range for a day or 2 when it is over 95 degrees outside. We have a heater but never turn it on as it is not needed to be comfortable inside in the winter in San Diego.
That is awesome!
Depending on the type of spray foam used, for example if it is open cell, then the plumbing and electrical can be replaced with ease because the material is so pliable.
I live in Salem, Massachusetts. The summers are hot and humid and we have brutal winters. My attic has two bedrooms with crawl spaces on each side and small I unused area above. Those rooms have higher heat and humidity when it's sunny out. There's one gable vent and the soffits are closed.
In my opinion, I should add ventilation to the soffits, foam in the bedrooms from above and the sides and possibly add another gable vent on the other side of the house?
Building a home in western ma. Roofer is telling me he replaces rotten plywood from spray foam not allowing plywood to breath. Foam guy says he never gets complaints- roofer says he wouldn’t the roofer gets the call. Not sure what to do - Open cell on roof plywood or closed cell on floor install vents and cellulose on top of it. I will have HVAC trunk and hoses going to second floor rooms.
Absolutely true, I don't care what this slick guy says! The fact is that putting insulation on the bottom side of your raptors is not good for your roofing at all!
I have a home in N.Arizona completed in the summer of 2018. Beginning the winter of 2018 we stared noticing gaps opening up at the top of walls in several locations at the ceiling. This has been an ongoing issue and we have since learned that it is truss uplift. A bad drywall “patch” job by the builder has failed to address the issue. We have spray foam insulation on the floor of the attic and the attic is vented. Do you have any recommendations on how the attic could be insulated to help prevent this from reoccurring? Thank you.
I talked to a company today in Vermont that might get the job. I have a ranch house that is 30x60 ,and one option he suggested was 1 inch of closed cell on the sheet rock /ceilings followed by 12inches of blown cellulose . and that would give me R49. Thanks for your video.
Can be risky.. As closed cell has allot of power when it expands and if it gets between sheetrock and the beam.. It can push them apart. Good thing is..once it dries it glues them back together.
I currently have a ridge vent and soffits around the house. I want to spray foam my attic rafters. My goal is to keep the attic from getting excessively hot in the summer months. I live in CT. Hoping this would ultimately reduce my HVAC from over working at times. HVAC is in my basement. I would like to also spray foam my garage ceiling to help keep the kids room above stay a bit more warm in the winter. Your advise would help. Thank you
Spray foaming the attic roof deck would help keep the attic temperature close to the rest of the house. In this application, the vents would be sealed up.
Thanks great video I getting my attic foam insulated by doing the whole attic the moisture will keep out? Thanks again
If your attic has moisture issues you will want to identify where the issue is coming from first. If the roof is letting moisture in and using our spray foam over that, it will cause more problems.
In Miami, we have a very slight roof slope. Thinking of spray foam on the roof deck, but two questions:
1) how do you get into the tiny space when the slope of the roof is so slight? And removing the existing blown in insulation is going to be extremely difficult for the same reason.
2) When new roofing shingles are nailed down in Miami the inspectors want to see the nail points coming through the roof deck. With spray foam it will be invisible forever. How do you get around this?
I don't know about how to spray, but you should get PICTURES of the roof installation showing the size of the nails they use. Show the box with nail or staple size next to the guy using the gun and a close up. It happens all the time that inspectors cannot see everything. This would be one of those cases. But the pics should suffice. Or - being Miami - maybe a $100 bill.
i know your saying rafters need no ventilation. would it be a big issue to leave the ventilation and spray the rafters? i have soffit and ridge vents on mine now. there is fiberglass roles on the floor and 2 ac units and duct work in the attic. so other then the vents it sounds like rafter would be better for myself. i live in very hot climate 90+ most of the year. so i was thinking rafter insulation to keep the heat out and the vents will allow any heat to escape but i obviously cannot condition the air due to the vents. would this be any value? wouldn't the rafter insulation keep the transfer heat out and the existing floor insulation keep it more out of the house and the vents allowing heat to escape and still end up with a cooler attic space?
can i air seal with foam over the insulation that wraps the ducts (ducts are in the attic)?
I live in Arizona and would really like to keep the hot sun from heating my attic and making my AC work harder. I feel like spraying the rafters in my case is the right thing to do, but I am concerned about moisture issues (Even though we have VERY little rain and very low humidity, never hurts to be cautious 🤷🏻♂️), and the thought of having nothing on the floor doesn't sit right with me. I've talk to so many insulation contractors and none of them give me the same answer, some change their answer mid-conversation >.
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You will be able to find the closest retrofoam dealer to you and if they service your area. They will most definitely be able to help you out.
If you have any questions for us we would be more than happy to answer for you! You can email us at retrofoamofmichigan@gmail.com
The problem is that if the roof can't shed the heat indoors, then the roof shingles will get hotter and degrade faster. Also in the summer, a cold roof is better, so snow blows off the Cold Roof and doesn't melt and refreeze on the roof, damaging the shingles. Also, sealing in the roof can cause humidity get trapped and cause mold issues unless you have a dehumidifier up there. Put in an Attic Fan and Save your Roof. Insulate the floor if you wish.
If you have appliances in your attic (HVAC comes to mind) and you’re burning gas in the furnace, think hard about the combustion air supply and the burned gas exhaust - so you’ve sealed the soffit vents and the ridge vent… where’s the makeup air coming from? And the CO (carbon monoxide) and other gases venting?
I'm thinking ... do the attic roof (2×4), keep my 3 roof vents w option to close or open and do my attic floor (2×6). I'm using it for storage and plan to put down a 1/2 plywood floor. Both sound expensive but we have rebates that are huge so I'm like - why not. Aside from insullation for air and sound the foam stops bugs and for my 70 year old home will add to structure. I did the walls for $2,500.00 but got $900.00 back in rebate.
We recommend spraying either the roof deck or the floor because they are two opposing systems. If you decide to do the roof deck there would be no need for vents.
Thank you for this video and helping others. I'm in Texas with an HVAC system in the attic. The attic currently has vents on both gable ends and roof vents as well as soffit vents. If I decide to insulate the undersides of the roof deck, do these vents need to be closed up?
Hey Paul! If you choose to spray the underside of your roof deck we recommend closing off your vents. That area would become a conditioned space, making vents unneccessary.
If you currently have a traditional attic with soffit vents/ ridge vent and attic floor is fiberglass insulated... now you want to spray foam insulate the roof rafters, do you now need to remove the attic floor/ above your house ceiling fiberglass batt?
We have a gambrel roof on our shed & converting it to a guest cottage. (It has a ridge vent, shingles roof & log siding. No soffits. We want to use tounge n groove pine all the way up to the ceiling. Do we use close cell spray? Regardless what we use how do we work around the interior side of the ridge vent? Your advice/suggestions are appreciated. We are at a stand still, can't find info. Thx!
For this application, I would recommend using an Open Cell instead of a closed-cell foam. Closed Cell will hide any leaks which will cause extensive damage. Water can pass through the Open Cell making leaks detectable before any large amounts of damage has been done.
With our foam we would spray right over any vents and the little cottage would then be an unvented system!
I have a finish basement would just spray foam from the expose ceiling the knee wall to the soffit as a hot roof is a good idea and what options I have to spray foam the finish part do I really need to take down my finish ceiling. Thank you
Yes, the "hot roof" system is recommended for that. Cutting strips in the slanted ceiling section to spray foam is usually the best way to insulate and seal that area.
Thank you foam University, building a house in south west Florida thinking about foam insulation for the rafters. It is very humid also thinking of asphalt shingles would that be OK?
That shouldn't be an issue. Good luck with your project!
What about ridge rot with the opencell? I hear two different answers.
I live in the humid south! Thinking which would be a better option. It’s a new home my insulation is good it’s blown in and I have radiant barrier roofing. I feel like if I put the spray foam in the rafters it will be a good choice. I honestly don’t want to do the floor/ceiling of the attic I want to still be able to have that ease of adding electrical work without having to cut into $1,000s worth insulation. I have the vent ridge what would be your suggestion?
Our standard recommendation would be to remove any of the blown in insulation from the attic floor and spray foam onto the roof deck. Sealing off the vents. Install mechanical vent if ventilation is needed
I have a ranch with blown in fiberglass insulation, soffit vents and ridge vent. The blown in insulation has settled and we have alot of wind and some of the blown in insulation has been blown away from the windy side of the attic edge. I want to improve my attic insulation - should I add fiberglass batts without vapor barrier OR suck out loose fiberglass and spray foam roof rafter after sealing up roof vents. Money wise the batts are going to be cheaper - will the house sweat if the spray foam is used? What would you do?
We would recommend spray foam. Your house "sweating" really depends on your lifestyle and how well your house is mechanically vented.
If you foam the attic rafters and don’t have a vented room, then is it not recommended to have gas heat or gas hot water tanks? I’m a fan of the gas solution and am wondering if I would be able to do those with a vented roof if I spray foam the attic floor. Also if you foam the floor can you put cellulos on top of it to increase the R value?
Yes. you can use gas appliances with an unvented attic system. You could put cellulose over the top of spray foam. However you will not see a reasonable cost return if you do that.
In Connecticut, my 45 year old attic has a central air handler, no soffits so no soffit vents, I do have gable vents and a ridge vent. Choice of insulating attic deck or floor. Either requires the foam have ignition barrier sprayed on at added cost. How about spraying 2” of closed cell foam on attic floor (to air seal and insulate) then cover foam with rock wool batts (for ignition barrier and insulation)?
We do not recommend a flash and batt system. That is prone to moisture issues. For your situation I would recommend open cell foam on the roof deck, followed by the appropriate barrier. An adequate mechanical vent in the living space should exhaust excess humidity out of the house.
I probably know the answer, but I’ll ask anyways. Do you spray the gable walls, when spraying the roof deck?
Yes, we would spray the gable walls when spraying the roof deck.
It seems to me that having spray foam between the rafters AND fiberglass between the ceiling joists would provide improved overall insulation of your heated floor space of the house. As an example, I had a house (built in 1969 in Albuquerque, NM - the desert) that had fiberglass ceiling insulation, a wood roof deck, and asphalt shingles. Summer attic temperature reached 137 degrees Fahrenheit. Later I moved into a new house in a similar weather environment (the summer temperatures were up to 103 degrees (F) in both places. The new house had similar insulation, but the new house had a radiant barrier under the roof decking. The attic temperature in the new house never exceeded 117 degrees (F) even in 103 degree sunny days. What a difference the radiant barrier seems to make. If the heated floor space is 70 degrees and the attic is 117 degrees, it should be easier and cheaper to maintain a comfortable environment in the living area of the house. If one were to add spray foam under the roof decking of the new house with radiant barrier, wouldn't it further reduce the attic temperature in the attic, thus reducing the temperature differential between the living space and the attic and making it easier and cheaper to cool the house in the summer (and heat it in the winter). That is my reasoning on the issue. Why, then, do you recommend removal of the fiberglass insulation between the ceiling joists after installing spray foam under the roof deck? Just curious...
because you don't need it anymore with the rafters/decking insulated with spray foam. you want the air from below to reach into the attic without added obstruction in its way (i.e., insulation).
We would never recommend putting insulation on the roof deck and the flat. They are two different systems and require different air flow/circulation. I would also never recommend covering radiant barrier It needs to reflect heat. Here's another video that goes into this more th-cam.com/video/DswkpbHPWi0/w-d-xo.html
I had spray foam installed on my attic rafters/roof deck. was to be 3 inch but some places is only an inch, is this a problem? Also is there specific range for the Dew Point to be in a sealed attic space? I was told it should be 0 but mine is much higher. Also with a sealed attic does existing insulation on the floor deck cause any issues?
Can I foam the attic joist floor and then later foam under the roof decking if I remove the vented soffits and ridge vent?
We always recommend one or the other, but not both. If you want to use the attic as storage or a second room, then spraying the roof deck is ideal. In this case, you don't need soffit or ridge vents and instead use mechanical ventilation.
If you spray the attic flat, you will still need the vents.
So I’m thinking about re-insulating my attic removing all the blown insulation and then sealing off my soffit and rafters with foam.
I do have a gas furnace do I need some type of ventilation for that??
Also would you recommend open cell or close cell
Your furnace should vent to the outside. Your furnace venting can be separated from the attic. We recommend sealing the soffit for an unvented attic system and using open cell spray foam, but every project is different. The article below goes into more detail about this.
www.retrofoamofmichigan.com/blog/vented-vs-unvented-attic-which-is-better
Would you recommend us putting in the electrical and hvac before spraying the walls. This was a really great video by the way. It was well produced.
Thank you so much for the awesome feedback!
We definitely recommend putting in the electrical and HVAC in before spraying the walls. It just makes the process for each one of these things so much easier.
I had my attic rafters and walls sprayed foamed (closed cell) a few yrs ago. Surprisingly I didn’t notice much reduction on heating costs. I’m thinking of insulating the attic floor, with fiberglass, (kind of thinking I should have went that route instead of heating the entire attic which is unused). I guess my question is, will that help and if I do should I now vent the attic since it will be completely insulated 360 degrees?
If you had your roof deck sprayed with foam, you don't need vents as it is now part of the conditioned space.
We never recommend doing both the attic roof deck and flat.
The best suggestion here would be to contact your insulation contractor to come out and take a look to see if there could be an air leak somewhere else in the house or possibly a spot was missed on the roof deck.
What was the outcome
Is it bad for the shingles to have insulation on the rafters? I'm concerned about the high temperatures here in Dallas, Texas.
The term we use for that is called a hot roof, which is one of the most common misconceptions of foam insulation. These are very dated ways of thinking about spray foam. Spray foam is actually considered a barrier between the heat and AC you pay for and the outside temperatures. Our main goal is to seal the building envelope and keep outside temps out and inside temps in! If you would like to dive a little deeper into this, you can visit this article on our website! www.retrofoamofmichigan.com/blog/does-spray-foam-damage-roof-shingles
Should I spray foam my rafters after I install my new roof or before....OR does it matter at all?...I live in northern Maine...and if I spray my rafters do I need a ridge vent on the new roof..?
We usually recommend spraying the underside of the roof, or the rafters, after the new roof has been installed. With this method, there is no need for any ridge vents because the attic is now part of the building envelope, meaning it will be a conditioned space just like the rest of your home.
I need to insulate the roof cause I turned my attick space into a room, what’s the best thing to go with ? My contractors covered the walls with sheet rock. I also have an AC unit put in here
Spray foam insulation is the best option.
How about spraying both, the attic raffters and attic floor ?. Could I get a better insulation like that?. Also I guess will need ventilation for sure , right?.
The biggest thing to keep in mind is that if you decide to insulate the attic floor, then you're going to need ventilation. Insulating the attic rafters creates a conditioned space where your attic is the same temperature as the rest of your home. You don't need ventilation if you decide to spray foam the rafters. This article from our Learning Center contains some additional information on this topic that you may find helpful: www.retrofoamofmichigan.com/blog/spray-foam-attic-floor-or-rafters
How important is sealing the switch boxes and light cans with a roof foam job?
This is definitely important because a lot of drafts could happen around these areas. We talk about insulating around can lights in this video th-cam.com/video/Y14b3HmwURY/w-d-xo.html
Building a home in south west Florida near the gulf cost could the spray foam be installed under side
Of the roof before or after the the tamko shingles are installed.
Builder said that he is having a hard time getting shingles but installed peal and seal on the roof and wants to install spray foam under
Side first to keep the project going l believe the shingles will come in shortly?
Hey Robert! As long as there is decking it should be fine.
Do you need to take out floor blown in insulation after close foam is installed
We always recommend removing any existing insulation before the attic is sprayed. Even if you're spraying the roof deck and you have blown-in insulation on the attic flat.
I'm going to closed cell spray foam my roof deck in my garage with an open ceiling to keep it warmer in the winter. Now for the summer should I put in vents that are are to open and close, open for summer to release moisture, closedfor winter or is that unnecessary?
Because you're going to spray the roof deck, you won't need any vents! An unvented system relies on an air seal to make the attic a conditioned space, and that's exactly what you will do when you spray foam that roof deck.
If you'd like some more information, you should check out this article from our Learning Center: www.retrofoamofmichigan.com/blog/vented-vs-unvented-attic-which-is-better
Have seen many older homes spray foamed with the ridge vent left open. Seems to work extremely well. Is it recommended? Iam an hvac contractor here in Houston Tx.
It depends on what the homeowner plans to use the attic for.
If they plan to use the attic as storage, we recommend spraying the roof deck. If they don't have any plans on using the attic, then the attic floor would be the better choice.
If the roof deck is sprayed, there is no need to have the vents anymore.
They plan to use the attic. The ridge vent was left open for combustion for a standard 80 afu gas furnace, water heater....etc
We were thinking about offering it as a package deal when they purchase new hvac equipment. After we do a load calculation .
I am wanting to know about spray foaming and older house that has traditional fiberglass insulation in it. Do I have to remove the insulation on the ceiling joist when I spray foam the rafters. I have been told both ways. Which is best and why?
The old fiberglass does need to be removed.
One reason is that it is old, dirty, and has retained any allergens and pollutants that have moved through it.
Another reason is that the spray foam needs a clean space to adhere to.
This article has a lot more details about the "why" it should be removed.
www.retrofoamofmichigan.com/blog/remove-old-insulation-before-installing-new
Is a fire barrier required for either floor or rafters installation. Does the answer change if there are appliances in the attic?
A thermal barrier may be required if there are mechanicals in the attic. It would be best to discuss with your local building inspector.
Also spraying the hole house rafters would that be ok with no ventilation?
If you are spraying the roof deck no ventilation is necessary. This turns the attic into a conditioned space.
In Georgia, have a home with a tongue and groove ceiling between the main level and the attic. No insulation currently, it's a 1950s remodel. Soffit vents, gable vents, and ridge vents are already there. We plan to put sheetrock over the tongue and groove for the ceiling but want to leave the tongue and groove as an "attic floor" below the studs and for stability. We do not plan to use the attic for anything other than light storage and possibly HVAC system (it's currently in the crawlspace). What is the best way to ventilate?
Hey Andrew! We recommend spray-foaming your roof deck and closing off all vents.
If you’re going to move the HVAC unit up into the attic, and you have a gas burning furnace in the HVAC system, you’re going to consider what you will do about makeup air for the furnace, and what you will do about the exhaust gases. In other words, you’ll probably need a vented attic. Why not just leave the HVAC in the basement?
By the way, a plaster ceiling would probably be a better choice rather than the Sheetrock. Plaster “breathes” and will pass water vapor. It’s a little more work and money, but over the long term save yourself mold, mildew, and rot problems down the road, seeing as you intend to keep the tongue and groove lumber
I'm about to build a pole barn, can you insulate the ceiling floor with spray foam? I only have seen the roof sprayed with insulation.
You can spray the ceiling floor, but we usually recommend spraying the roof deck.
No one has mentioned what is does to the shingles when you trap the heat from the shingles above and don't allow cooler night air to cool the underside of the roof deck at night. Premature aging of the shingles.
This is actually a common misconception. Check this article out. www.retrofoamofmichigan.com/blog/does-spray-foam-damage-roof-shingles
@@RetroFoamofMichigan Thank you! I have a 12/12 pitch roof so it still didn't make sense to spray the roof deck at twice the cost. I sealed the ceiling and blown insulated on top of that for an r-60 ceiling. My roofer was the most adamant not to spray the roof deck. He said it would shorten the life of the shingles by approx 10 years. If it has been about 20 years that spray foam has been used on the roof deck it may still be a few years before we see a downside?
In theory that is possible. However, all the anecdotal evidence over the past 20+ years points to that not happening.
I'm building a house and have already installed a roof vent and the soffit is vented but I'm looking into installing foam to the rafters. What do I need to do to get myself ready for foam? Is there an easy way, other that replacing the soffit to get ready?
For the soffit, the spray foam installer should be able to block off/seal the soffit so no foam gets through it.
This is also true for the roof vent.
I get way no “air” venting is needed if make attic a conditioned space but should there still be some type of vent at the highest roof ridge to allow for vapor/moisture to escape. I have read about ridge rot over time.
One more question... if I spray the rafters should I remove the fiberglass insulation on the floor.....
We always recommend removing the old insulation in the attic when getting spray foam. If you're spraying the roof deck, the old fiberglass isn't really adding anything. Plus it is old and dirty, so it's always best to get a fresh start.
What ventilation do I need if I'm using spray insulation in the ceiling deck rafters
Hey Karen! If you are talking about your roof flat (attic floor) you would need soffit vents and baffles.
Can you spray the rafters and have blown in cellulose on floor? Any pros/cons of doing this?
You will not want to keep the cellulose. It will cause a huge mess while the installers are trying to spray the foam.
I have furnaces in the attic but the builder put the insulation is on the floor of the attic when the home was built 28 years ago. I'm going to reinstate the attic, so should I switch to have the insulation in the rafters?
We would recommend having your roof deck done. With traditional insulations most of the time they have no other option but to put it on the flat.
Can I spray insulation between rafters even though my attic floor is insulated with old insulation with flooring installed over? The house is 100 yrs old so the insulation isn’t the greatest and I get really bad ice damming.
You can have the rafters spray foamed. With that said, you will want to remove that flooring so the existing insulation can be taken out.
If spray foam open cell, wall and ceiling, not roof rafters. Will I still have humidity problems and worries of air infiltration, such as range hood,bathroom vents. Ceiling joists rot. Or did I move all spray foam problems to the main living area and will still need separate dehumidifiers??
If you spray open cell on the attic flat, you're essentially sealing the attic off from the rest of the conditioned space of the home. You would still need to have vents in that case.
If you want to spray the roof deck, then the attic becomes part of the conditioned space in the home, and venting up there isn't needed.
Creating an air seal throughout the entire home can take care of any humidity issues you're having.
Gentlemen pls help, I have a 1920 colonial that I just finished gutting the attic and removed fiberglass insulation from the 60's or 70's and now I want to spray the rafters with open cell foam , but I keep hearing that the life of the roof shingles will be less because the roof can not breath ??second can't rafter vents/baffles in conjunction with foam help this issue
You will want to seal off the building envelope, so either insulate the flat and have vents or the rafters and go ventless. Here are some other articles we have on these topics: www.retrofoamofmichigan.com/blog/spray-foam-attic-floor-or-rafters and www.retrofoamofmichigan.com/blog/does-spray-foam-damage-roof-shingles
Here's an off the wall (no pun intended) question. What if you do both the roof and the floor in the attic with closed cell foam and use an active soffit system, instead of passive. Where you're using an air exchanger, that also helps with getting rid of excess humidity but at no cost of thermal inductive mass being pushed into the attic space.
I've seen some pretty exotic solutions over the years and wonder if you've seen, heard or even installed them.
Active vents are fine, although I would not recommend doing both the flat and the roofdeck. Those two systems will not work well together.
Great info, currently I have a HIP Truss Roof, with R-30 batt fiber glass. I want to air seal more than anythijng else. No appliances in the attic. Currently has ridge vent and soffit vents. Company wants to spray the rafters(trusses?). Attic is not used for anything, not even storage because its truss. company wants to spray the rafters, should I consider it or just have a company come and air seal under the insulation? Thanks.
It wouldn't make sense to pull the insulation back to spray under it. We would suggest that the insulation is removed completely and then sprayed. Once the air seal is done the existing insulation becomes unnecessary as air can not pass through the foam. There must be a reason this company is wanting to do the roof deck. We suggest contacting them and having them explain to you exactly why that area.
@@RetroFoamofMichigan Thanks, the company basically said because they are a small company they only do the rafters, I think because they dont have workers to remove all the old insulation. Sounds like a small mom and pop shop but very highly rated, so IDK what to think. It sounds like you feel since my attic is already heavily vented and no appliances in the attic (I may add a 2nd air handleer up there down the road though) doing the floor makes more sense?
Also, they use close cell foam and based on your other video, it sounds like open cell would be better. Also, I am getting solar panels on the roof soon, so when you said closed cell would hide any leaks that was a big concern since I wont know if the solar installers cause leaks and will be very hard to figure out where the leak is if there is one.
Thanks much.
@@mark33545 Yes, we suggest that any area inside the home is done with Open Cell since closed cell does have that possibility to hide leaks and other issues. With open cell it can pass through that foam.
I want to spray foam my rafters in my attached garage the mechanical ventilation doesnt extend to the garage, will I need ventilation in this scenario
That would depend on your specific area. If you live in a more humid state you would want that ventilation as an extra precaution. If you have any other questions let me know! I am happy to help!
If I am wanting to add spray foam to the rafters but I already have vents in the attic due to the insulation originally being batting on the floor, is that a problem?
It's not a problem, we would just recommend having those vents removed or covered before spray foam is applied.
Question...having the roof deck (underside of roof) sprayed with closed cell. There are 3 vents. What should be used to cover the vents to create that envelope?
Plastic over the vent then spraying over that would be best. I would recommend open cell for the attic.
@@RetroFoamofMichigan Why open cell instead of closed? If the rood develops a leak the water would permeate the open cell.
@@sanmurillo Open cell does not retain water and can actually move through the foam easier. Closed Cell can hide the water leaks and cause more of a problem in the long run.
@RetroFoamofMichigan is that tested or hear say or theory open vs closed roof deck.
I'm planning to build a house. I would like to do a fully sealed house, including an unvented attic. What are the code requirements for closed cell foam adhered to the underside of the roof deck?
My local building inspector is saying it still requires r49. Is that right? Or are there different requirements for cathedral ceiling applications like this? (I'm in climate zone 6, we Idaho)
My house is relatively new and is energy star certified with R60 open cell foam under the roof deck. If you are planning a new house, in my opinion there is no better investment than insulation, so I wouldn't worry about high R-value requirements.
I'm glad you found your answer on our other video!
That is awesome, Dave! We couldn't agree with you more.
I have a slate roof, would it be OK to insulate the attic rafters with spray foam? Also, I have a small attic fan in my roof. Once the spray foam goes in, how can the attic fan be replaced if need be?
You can absolutely add spray foam to the attic roof deck if you have a slate roof. There's no problem.
When it comes to your attic fan, you can build a box around it that can be sprayed over. That way, if it needs to be replaced, you can still access it.
I have sprayed under-my roof deck with open cell, but my house still get very hot in the summer time, i have been considering spraying the top ceiling Joist too... would I need to ventilate my attic too? Or is this something you recommend?
I dont have central air, I have mini ductless units in my house
Open cell spray foam on the roof deck should have you covered for that space. This is also an unvented attic system, so you wouldn't need any ventilation.
If the insulation in the rest of your home is lacking, this could be why you're still experiencing comfort issues.
Below I have linked our article about unvented vs. vented attics that you might also find helpful.
www.retrofoamofmichigan.com/blog/vented-vs-unvented-attic-which-is-better
Unfortunately what you really need is to ventilate the upper roof deck. What I mean is you need an additional roof OVER your original roof, with an air space between the two roof systems. What’s happening now is that your roof covering (shingles, probably) and the plywood roof deck are absorbing the sun’s heat and transferring it into the attic. Doesn’t matter that the rafters are insulated. There are many ways to make an unventilated roof work, but the most effective is the over-roof with air flow under it.
By the way, since your attic isn’t ventilated, it’s probably really really hot in there; maybe 150-170° degrees? That heat is burning the back of your asphalt shingles, if that’s what you have.
I live in a townhouse (4 plex). We now have rolled out insulation on the attic floor which rodents are currently enjoying. We are thinking of removing that insulation and using either spray foam or blown in for insulation. I don’t think we have the ventilation for spraying the floor. Any suggestions? I’d like to get rid of the rodents at the same time.
Any pest issues would need to be taken care of before you add any insulation.
Typically speaking, ventilation is relatively easy to add to an attic space.
My roof is metal and I have sprayed-foamed the rafters. I also have installed fiberglass insulation on the floor of the attic areas. So, do i need to vent the attic space or not?
If the gables and vents are sealed then the fiberglass needs to be removed.
@@RetroFoamofMichigan I don't have vents yet. my question is do i need vents?
@@ronkelley415 No, venting is not necessary if the attic is sealed (gables and all)
If you insulate rafters don’t you need baffles to keep wood dry and help cool between shingles and insulation to keep shingles from baking?
A roof deck application should also be a ventless system, so there's no need for baffles.
So what happens if you already have vents in the attic but want to go with spray foam?
Spray foam in the attic is a ventless system so they would seal up any of the vents!
Wjat happens if you do the roof deck and the floor?
We don't recommend doing so. Not only is it a waste of money, but it could potentially cause moisture or air pressure issues.
I have gable and ridge vents. House built in 1905. Would foam board on the floor cause moisture issues from inside the house? I live in a mixed area, meaning heat in winter, cool in summer. Central wa state. Thanks!!!
Hi Dan, The house will likely need some form of mechanical ventilation. A bathroom fan might work just fine.
@@RetroFoamofMichigan appreciate that. Over thinking things seems to be my new normal with learning about insulation. I want to air seal the attic floor but not vapor barrier from what I’m reading
Insulation can definitely be a lot to learn about. We also have articles that go more in-depth on some topics if you want to check them out! www.retrofoamofmichigan.com/blog/spray-foam-attic-floor-or-rafters
@@RetroFoamofMichigan I’ll take a read. Thanks so much
If you have appliances in your attic (HVAC comes to mind) and you’re burning gas in the furnace, think hard about the combustion air supply and the burned gas exhaust - so you’ve sealed the soffit vents and the ridge vent… where’s the makeup air coming from? And the CO (carbon monoxide) and other gases venting?
The HVAC system itself should exhaust any combustion gas.
I want to spray foam my roof rafters. However, thinking of getting a new roof in about 2 years. Should I wait for new roof to be installed before spraying?
Yes, you should wait to add the spray foam until after you get your new roof.
@@RetroFoamofMichigan thanks.
No problem at all!
Just had an ugly cellulose/fiberglass missmatch replaced with foam on the attic floor. Just looking around TH-cam to make sure I didn't do something incorrect. (already had the venting)
Was it any difference
@@DR-um2bv Do you mean between the "cellulose/fiberglass" and the foam? I don't know the quality of foam, but we don't have a missmatch anymore and everything is covered. It's a lot easier to breathe up there and to move around.
If they spray foam the attic floor will they spray the soffitt vents if I have gable vents?
If the attic floor is sprayed, then the installer wouldn't spray over the vents. It's only in an unvented system that the foam is sprayed over the vents.
@@RetroFoamofMichigan Is it more expensive to spray the attic floor and will they fill the whole cavity to get it up to an R60? Rough ballpark for attic floor spray foam?
It all comes down to the size of the attic. Sometimes it can be cheaper to spray the floor because the roof is steep.
The other thing to consider is the air seal that foam creates. Blocking airflow with foam supersedes the R-Value.
This article talks more about the amount of foam that is recommended to be sprayed.
www.retrofoamofmichigan.com/blog/spray-foam-insulation-thickness-requirement
Open cell or closed cell foam for an attic floor?
We recommend open cell spray foam for the home, including the attic, open walls, rim joist, and crawl space.
@@RetroFoamofMichigan - I thought closed cell offers better water protection
@@vancouver4sure closed cell spray foam doesn't allow water to move through it. That seems great in theory, but that also means that it hides the leak which can lead to more damage. Open cell still allows water to move through it without doing any damage to the foam and also alerts the homeowner where the leak is located.
Is it ok to apply spray foam insulation when the attic is 110 degrees? Will it fully cure? Or will it off gas forever?
If the substrate is in good condition, yes, it would be fine to apply spray foam under these conditions.
I have a victorian house from 1900 with only 1xs, tar paper and then 50 year shingles on the roof. there are 3 whirling attic vents at the top of the steep roof and a 24x30 louvered gable vent. Currently there is plywood on top of modern 2x4s and then r19 insulation between the very old true 2x6 ceiling joists. Heat pump, trunk line and flex vents will be installed in the attic to service the second floor. Trying to decide whether to add more fiberglass between the ceiling joists or to go with open cell foam on the attic roof. If I go with the foam, I will have to have a supply and return in the attic due to the insulation top and bottom of that space. thank you
Hi Katie,
I would recommend removing the old insulation on the floor and installing open cell spray foam on the roof deck.
If spraying the rafters, Will it cause a shorter life cycle of the shingles on the roof?
Good question. We wrote an article about that here: www.retrofoamofmichigan.com/blog/does-spray-foam-damage-roof-shingles
Yes it does! Roofer speaking here, in fact there are a few videos on here that show entire roofing systems damaged by doing spray foam to the underside of a roof. The Heat is made to disipate through the ceiling of the roof, however without proper ventilation the roof can delaminate or the shingles adhesive stops sticking to other shingles causing whole sections of the roof to lift and fly in the wind. There are also manufactureres that have Ok'd the use of rafter insulation. But they are few, most Insulation Manufactures Void the Roof Warranty without proper roofing ventilation.
@@david9797 We have never seen any of our projects have these roof issues. Keep in mind there will always be many factors that can lead to roof failures, including installer error.
@@david9797 so basically the shingles are just getting hotter and breaking down quicker?
Don't if you spray the rafters, over time (5+ years) it will trap moisture in the plywood between the singles and the insulation- causing it to rot?
Over the 20 years we have been insulating homes, we have not run into this problem.
I bought a house 1 year ago that has spray foam insulation on the rafters with an open floor in the attic. I'd never had a house with spray foam insulation on the rafters, but it works GREAT. Question, the builders blocked off the garage when applying the insulation, therefore, there's NO insulation over the garage -- either on the rafters of the ceiling floor. Therefore, the garage gets very hot in the summer. What's the best way to fix this problem? Add spray foam insulation on the rafters?
Yes, we would recommend adding Spray Foam to the garage as well.
And look at all the foam being used in mattresses! Damn! For me, it's too hot! And what are the long term health effects? I can't find a mattress without foam in it! Yes, I'm still looking!
That's not really in our wheelhouse as we only provide foam insulation. The products we use are non-toxic and environmentally friendly.
Would you ever do both? Is there ever a situation where you would? My climate ranges from +30c to -30c. Thanks!
We would never recommend to do both because once you did one you'd already have the air seal plus it would be a waste of money. Now, which method you choose comes down to what you'd like to do with the attic space. If you want to use it for storage, then the roof deck is the way to go. If you don't plan to use the attic at all, you could do the floor and seal it off from the rest of the house.
@@RetroFoamofMichigan Thanks for the info. My house already has fiberglass insulation on the attic floor, but thinking of adding foam to the attic deck. Still, wouldn't recommend it? My house built in 2004, so naturally insulation has settled, and it's 100*+ now in the summer here in south Texas! AC unit in the attic.
@@reydelagarza2953 similar situation here. Hoping for a response
@@RetroFoamofMichigan Doesn't it cost you more in energy to do the rafters since your are heating the attic space too? I need to insulate for real cold, a R-49 at least. So I would need 7" of closed cell foam, right? So isn't 7" on the attic floor the best way to go? I won't be using the attic for anything.
@@jeffwilliams7164 no, it doesn't use more energy overall. You are heating more volume, but it is doing so more efficiently. It also helps protect and prolong the roof and attic area. Also, instead of trying to hit that R-49 prescriptive measure, I would recommend using a performance method to meet code. Here's an article that goes more in-depth.
www.retrofoamofmichigan.com/blog/spray-foam-insulation-code-requirements-pass-without-meeting-prescriptive-r-value
Can someone insulate their rafters and attic floor? Would ventilation be required?
If you're looking to insulate your attic, you can either go with a vented or an unvented system. Spraying the attic floor creates a vented system, which is great for resisting heat transfer and allows for airflow. Spraying the roof deck (the rafters) creates an unvented system, which relies on an air seal to make the attic a conditioned space.
This article from our Learning Center contains some additional information you may find helpful: www.retrofoamofmichigan.com/blog/vented-vs-unvented-attic-which-is-better
@@RetroFoamofMichigan Thank you so much for the reply. To rephrase my question, if both the floor and rafters are insulated, there is just dead space, i.e zero ventilation. Is that a bad thing?
Yes, it wouldn't be the best. Because foam insulation creates an air seal, spraying both the attic flat and the rafters would cut off your attic from the rest of your home. You wouldn't be able to get in or out of it, and it would just trap hot/cool air. It would be completely useless, unfortunately.
I hope that made sense! We're here to answer all of your questions.
@@RetroFoamofMichigan this is a space where there are trusses on trusses so the space won't be used. The builder wants to insulate the roof but I believe in insulating the living space directly. Also I think the soffits and roof and currently vented as insulating the roof is a plan change.
Yes, insulating the roof deck (with foam) should be a ventless system. That means that, yes, there may need to be some changes to what the house has currently.
If insulating the attic rafters, using open cell foam, what do you do with the big triangular vents on each end of a gable roof? How do you make it air tight without getting the foam wet in a heavy rain?
Also, won’t moisture vapors transfer into the attic, from outside, though open cell foam? I live in north Florida if that makes any difference.
Gable vent would be covered and sprayed over if there are big gaps in or around them. Also we have never had any issue with moisture coming through the foam (outside of a roof leak or other major penetration).
If you insulate the floor - the stairwell or drop ladder will not have the same level of insulation as a roof insulation.
What about the safety of spray foam insulation? I have seen horror stories and documentaries in which the homeowners have been driven out of their houses due to the spray foam vapor leaking into the house and causing serious health issues..
We address this question specifically in this video: th-cam.com/video/nS4lfHjmP1k/w-d-xo.html
Wouldn’t the floor, and roof, of the garage attic need to be foamed, to not only seal the whole attic, but to keep car exhaust fumes from getting into the conditioned space? There is no simple way to separate the attic space over the garage from the attic space over the living area.
If there is a bonus room over the garage, yes the bonus room floor (garage ceiling) needs to be insulated/sealed.
@@RetroFoamofMichigan , what I’m thinking is that with the attic roof sealed, exhaust from the cars, in the garage, will slowly build up in the attic. This is because the garage attic is open to the rest of the attic. Therefore, the home’s A/C unit will begin pulling the exhaust into the living space, as the attic is now part of the conditioned space.
This would also, in my mind, be the case with the hot air in the garage (I live in Florida), being drawn into the conditioned space. So, why wouldn’t the attic floor also be sealed, to prevent both of these situations?
Thanks again
@@Detectken Simplest solution; add a mechanical vent on an outer wall.
I need help my downstairs is always closed which installation will be good for my house is about 19 years olds.
We compare some of the most common home insulation types here www.retrofoamofmichigan.com/blog/foam-fiberglass-cellulose-best-insulation-existing-house
Spray foam in crawl spaces just as bad it encapsulated the rafters and beams trapping moisture in wood leading yo rotting the wood
We like using open cell spray foam as it will allow any moisture to pass through the foam.
If you do the floor you won’t have easy access to wiring if need e
Joe, Open Cell is very easy to cut through which is why we recommend Open Cell for areas that need access. You can easily cut out the chunk you need then replace it back afterwords.
Spray foaming the rafters is just dumb. If there's a problem with your roof, say a few years after installation, diagnosing it has now become that much harder because all that crap adheres to the roof structure. You'll love seeing your minimal energy cost savings go bye-bye as roofers take four times as long to find and fix a problem area after which you have to pay to have new foam sprayed in. Living in one of the coldest areas of the country I think I can say with some knowledge that sacrificing a little R-value in the attic and finding efficiencies elsewhere that don't compromise the most critical component of your home is the smart thing to do.
This is why we recommend open cell for all living spaces. Open cell is a lot more manageable than closed cell. As for leaks and roof damage, water can pass through the open cell so it does not hide any leaks. The foam is easily removed and it is best to go with a reputable contractor that has a lifetime warranty. We offer a warranty on all of our work and product for the lifetime of that structure. If a customer has a roof leak and has to remove a small part of that foam to repair the roof, we would come back and respray that portion covered by the warranty. Hope this clears up some confusion.
Should insulate floor joists and rafters. #TheEnd
Stop being cheap people and build properly.
When adding foam insulation, you wouldn't need to do both. Generally, we recommend insulating the roof deck because it helps protect against ice dams and makes the attic part of the conditioned space of the home.
@@RetroFoamofMichigan Yup. I agree about roof decking. How do you all create a 1 inch air gap between the decking and insulation? Assuming the house has radiant barrier decking.
We don't create that air gap because, with spray foam on the roof deck, it is a ventless system.
Is anyone else's first question, what in the world is he wearing?? That suit jacket is hideous.
I have come to accept that not everyone appreciates the red velvet jacket...
I'm having a company spray foam my attic along the underside of the roof sheathing. Right now there is currently fiberglass insulation in the ceiling, should I remove that insulation to help the attic be at a more constant temperature?
We always recommend removing any existing insulation when adding spray foam to the attic, whether it's the roof deck or the attic flat.