I have trusses in my garage that are 26" appart. I can't find any fiberglass that is that size. I was thinking about using the rigid foam board to cut-to-fit in between the trusses or over tham to help keep the heat from coming through the garage's roof. I'd like to keep the open feel of the garage and not close off the ceiling/use blown in insulation. Any ideas? How did you insulate your garage roof?
insulation between trusses?
- Thread starter 1967marti
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matouse3
Well-known member
Spray foam would be my first choice. Its expensive, but worth it. Foam board would work, but its a hassle to cut and isn't cheap either.
I can do 3/4 foil backed foam board for under 150, spray was going to be around 3 per sq foot... I also would worry about if any leaks sprang up i would not be able to find them if everything was coated with spray foam.
I have designed out a fan/ducting system to pull air through the 4inch gap between the foam board and the underside of the roof underside that should all but eliminate any heat that would come through the roof. But I’m worried that I can’t see the forest for the trees and am over complication this issue. My biggest issue is that most solutions to this problem that I have been able to find are solved by adding a ceiling and blowing in insulation, this will not work for me as I like the open feel of the trusses and also plan on adding in a lightweight overhead trolley system in the near future. The roof is brand new and has white shingles, so construction wise I was shooting for a cool-roof design but I didn’t expect it to still be this hot in midsummer.
I have designed out a fan/ducting system to pull air through the 4inch gap between the foam board and the underside of the roof underside that should all but eliminate any heat that would come through the roof. But I’m worried that I can’t see the forest for the trees and am over complication this issue. My biggest issue is that most solutions to this problem that I have been able to find are solved by adding a ceiling and blowing in insulation, this will not work for me as I like the open feel of the trusses and also plan on adding in a lightweight overhead trolley system in the near future. The roof is brand new and has white shingles, so construction wise I was shooting for a cool-roof design but I didn’t expect it to still be this hot in midsummer.
matouse3
Well-known member
What kind of R value are you getting with that 3/4" compared to the spray foam? I would doubt you get much with the 3/5in board. The foil will help, but I question how much.
The leak issue is a concern with the spray foam.
Whats your geographical location- What kind of weather are we talking about?
The leak issue is a concern with the spray foam.
Whats your geographical location- What kind of weather are we talking about?
JakeKohl
Well-known member
I think that foil backed foam board is like an R3 insulation value...which is not much for a roof/attic. You'll need several layers of that to achieve any decent insulation value.
green.bubbly
Well-known member
I think it is a little higher with a proper air gap. I am installing 1" EPS under my steel roof. Cost me just under 8 bucks per sheet from my local lumberyard. Considerably cheaper than the big box stores.
How many square feet do you have?
Highbeam
Well-known member
How "open" can it really be with trusses 26" apart? My trusses are 12 feet apart and I wouldn't call it open.
Your desire to leave that framing exposed will cost you.
Your desire to leave that framing exposed will cost you.
Why not use the rolled paper backed insulation and cut it at 26.5 or 27 inches it will take a little longer but will get it done. You may want to throw some furring strips up also to help hold it in place if your intention is not to finish the ceiling any time soon.
Highbeam
Well-known member
Sounds like the intention is to staple batts to the top chord of the trusses. The kraft paper would allow you to reach 26" spacing. So even though the proper spacing is 24" for several reasons, the batts should work pretty well in a 26" space.
Beaumont67
Well-known member
I am going to use this, in my house reno.
http://www.insulation4less.com/Insulation4lessTechnicalArticles-24-Home-Insulation.aspx
Prodex Total Home Insulation keeps your home cool in summer, warm in winter and dry all the time....reduces your air conditioning and heating bills.
Prodex Total home insulation has a R-value of 15.67 (single layer), 21.10 (double layer), vapor and a radiant barrier component. The high R-value reduces your heating bills. The radiant barrier component of Prodex Total reduces you air-conditioning costs. The vapor barrier component protects your home from water damage, mold and mildew.
Attics and roofs: Heat gain is higher in the attic because the sun is beating down on it all day (it's not uncommon to have summer daytime temperatures in an attic cavity that exceeds 150 degrees F). Because heat rises, you'll have more winter heat loss through your attic roof than through your walls; therefore, it is more important having a higher R in the roof than the walls. The sun's heat is absorbed by a roof, heating the roof sheathing and causing the underside of the sheathing and the roof framing to radiate downward toward the attic floor. When a radiant barrier is placed above the roofing or directly underneath the roofing material, much of the heat radiated from the hot roof is reflected back out through the roof. This results in a cooler home and a reduction in your cooling costs.
Will the product hurt my shingles? No, absolutely not. There has been significant testing on this issue and it has shown that a radiant barrier installed in a residential attic will not harm the shingles.
http://www.insulation4less.com/Insulation4lessTechnicalArticles-24-Home-Insulation.aspx
Prodex Total Home Insulation keeps your home cool in summer, warm in winter and dry all the time....reduces your air conditioning and heating bills.
Prodex Total home insulation has a R-value of 15.67 (single layer), 21.10 (double layer), vapor and a radiant barrier component. The high R-value reduces your heating bills. The radiant barrier component of Prodex Total reduces you air-conditioning costs. The vapor barrier component protects your home from water damage, mold and mildew.
Attics and roofs: Heat gain is higher in the attic because the sun is beating down on it all day (it's not uncommon to have summer daytime temperatures in an attic cavity that exceeds 150 degrees F). Because heat rises, you'll have more winter heat loss through your attic roof than through your walls; therefore, it is more important having a higher R in the roof than the walls. The sun's heat is absorbed by a roof, heating the roof sheathing and causing the underside of the sheathing and the roof framing to radiate downward toward the attic floor. When a radiant barrier is placed above the roofing or directly underneath the roofing material, much of the heat radiated from the hot roof is reflected back out through the roof. This results in a cooler home and a reduction in your cooling costs.
Will the product hurt my shingles? No, absolutely not. There has been significant testing on this issue and it has shown that a radiant barrier installed in a residential attic will not harm the shingles.
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toyotadriver
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I have a shop building that has trusses placed on 48 centers. In my area, most buildings have trusses placed on 60 inch centers but I specified 48 inches. I put 1.5 inch foam sheets between the purlins and then double bubble foil and then the metal. I then covered the purlins and the foam sheets on the inside of the building with 1.5 inch foam sheets.
That left the trusses open for me to use for storage.
I am VERY impressed with how it insulates. We've had some upper 80s and a few 90+ degree days with the sun shining directly on the building. I went to the shop and checked the temp inside. It was about 68 degrees....about the same temp as the concrete floor. Basically, there is very little heat gain in the summer and so the shop building stays very comfortable even completely closed up. I'm a BIG believer in foam sheets. 3 inches of foam prevents most of the heat gain/loss.
1.5 inches of foam isn't quite enough by itself...there is still some heat transfer through the 1.5 inches foam...but 3 inches is more than plenty for most climates.
Here's a pic as it was going up:
That left the trusses open for me to use for storage.
I am VERY impressed with how it insulates. We've had some upper 80s and a few 90+ degree days with the sun shining directly on the building. I went to the shop and checked the temp inside. It was about 68 degrees....about the same temp as the concrete floor. Basically, there is very little heat gain in the summer and so the shop building stays very comfortable even completely closed up. I'm a BIG believer in foam sheets. 3 inches of foam prevents most of the heat gain/loss.
1.5 inches of foam isn't quite enough by itself...there is still some heat transfer through the 1.5 inches foam...but 3 inches is more than plenty for most climates.
Here's a pic as it was going up:
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Falcon67
Well-known member
The kraft insulation for 24" OC construction is cut at 22 1/2" with maybe 1" of extra backing on each side. It will not fit over a 26" gap. I had a few spaces like this under windows and it required extra insulation to fill the gap.
Motofixxer
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1" foil styrofoam has an R7 or so. You could also just sister a 2x4 etc to the side of your bottom truss chords to make it narrower.
Highbeam
Well-known member
Not concerned with the insulation but the paper. It is much wider than the batt. The 26" OC spacing makes a 24.5" cavity. This means you only need one inch of paper on each side and you know there is much more than one inch of paper.
i could cut up rolls of batts to fit between the trusses or use two 15" batts and some wire to hold it up... Even though the trusses are close together i like the open feeling and the ability to toss some stuff up there if needed...
I'm thinking of installing a fan on the peak of the gable first and see what that does for me, but i would still like to cut down on the heat that goes throught the roof.
I'm thinking of installing a fan on the peak of the gable first and see what that does for me, but i would still like to cut down on the heat that goes throught the roof.
Find a place local to you that supplies insulation for pole barns/metal bldgs. They can make up insulation any width you wantand thickness. Backing material is your pick. You do the research. Home depot is not the only place to get bats.
It came to me that every time I lose a dog they take a piece of my heart with them. And every new dog who comes into my life, gifts me with a piece of their heart. If I live long enough, all the components of my heart will be dog, and I will become as generous and loving as they are.” ~Unknown
It came to me that every time I lose a dog they take a piece of my heart with them. And every new dog who comes into my life, gifts me with a piece of their heart. If I live long enough, all the components of my heart will be dog, and I will become as generous and loving as they are.” ~Unknown
Motofixxer
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You would notice a huge improvement in the comfort level in the heat and cool season with even a little bit of insulation in the trusses. Insulate above before the side walls.
Drinkin-N-Thinkin
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I have a shop building that has trusses placed on 48 centers. In my area, most buildings have trusses placed on 60 inch centers but I specified 48 inches. I put 1.5 inch foam sheets between the purlins and then double bubble foil and then the metal. I then covered the purlins and the foam sheets on the inside of the building with 1.5 inch foam sheets.
That left the trusses open for me to use for storage.
I am VERY impressed with how it insulates. We've had some upper 80s and a few 90+ degree days with the sun shining directly on the building. I went to the shop and checked the temp inside. It was about 68 degrees....about the same temp as the concrete floor. Basically, there is very little heat gain in the summer and so the shop building stays very comfortable even completely closed up. I'm a BIG believer in foam sheets. 3 inches of foam prevents most of the heat gain/loss.
1.5 inches of foam isn't quite enough by itself...there is still some heat transfer through the 1.5 inches foam...but 3 inches is more than plenty for most climates.
Here's a pic as it was going up:
I have a metal pole building and will be insulating soon and was considering something along the lines of what you did on the roof; but how did you handle venting (it appears from your photo, the eaves and ridge are sealed on the inside, but is there an air space above that to provide air flow to a vent? Did you ever peek in there to check for condensation on a cold day that warmed up suddenly? With a metal roof (that is not standing seam) I feel the rubber washers used to attached the roof panels eventually will cook out with the temperatures up there and eventually become leak points--this is one reason I've decided against putting closed cell spray foam directly on my metal roof (walls & ceiling: yes).
Now if I were smart, I would have put plywood over the perlins, tar paper, furring strips to provide a gap, vents top and bottom, then standing seam metal and spray foam on the underside (but too late for me now)!
