Insulating in the corner of a pyramid roof

[Bob Coleman]

Hi All,

I'm planning to drywall my ceiling in the garage this weekend and I'm having trouble figuring out how to get proper insulation and venting into the corners. The garage has a very shallow pyramid roof (~3' rise in 10') and once the drywall is up I'm afraid I won't be able to access the cavity to insulate it. I'm also afraid that the insulation (I'm planning to use fiberglass) will block any ventilation into the space above the soffit.

I have considered just filling the entire space (including above the soffit) with foam before putting up the sheetrock.

Any advice is appreciated! Thanks.

[Peter Rawlings]

You're wise to think of it now. What you have is called a hip roof. No need to worry about the little bit of venting that corner might provide. I'd foam the blocking at the wall line and put some insulation in there before sheetrock....no need to fill the soffit.

If it were mine, I'd insulate the whole ceiling before rock, gonna be real hard to get into that area after. Low pitch and no heel on trusses/framing(?) is a booger. You could also have it blown after rock, but it's still a booger to get to. Assuming you've got vents up near the peak, be sure to put chutes in bays so you don't block vent path.

There's more we could talk about, I'll leave it at that for now.

[Joe Wiliams]

I have a similar situation coming up... I had been planning to just use blown in insulation after hanging the sheet rock. Now i'm contemplating using batts and putting them as the sheet rock goes up. Thinking it will be easier to access the shallow areas.

[Peter Rawlings]

In an ideal world the full depth of attic insulation would carry to the outside plane of the exterior wall, thus giving no loss of R value at perimeter. But it's almost always impossible. So think in terms of getting as close to the ideal as practical. Your working room in shallow pitch roofs is tight. Dancing on ceiling joist edges is hard enough,combine it with low headroom and it's just no fun.

One could put batts in the perimeter and then blow the rest after rock is up. You could also drop a ceiling to provide more working space, often not a workable solution, though. One other possibility would be to install mesh on the bottoms of joists, strap perpendicular to them, blow from bottom, then install drywall to strapping.

[Doug Carpenter]

I would just install kraft faced fiberglass batts in the corner I would not foam it or the gap between the 2 by and the roof deck. Might as well let it breathe a little. Hip roofs are difficult because they don't allow as much natural air movment like a regular roof. I would also install some baffles in the truss bays down above the walls so that the air flow doesn't get blocked by the insulation.

I can't tell by your post if you are blowing in fiberglass after the drywall. Or if you are planning on installing batt insulation before or after drywall. Definately address those corners from below before drywall.

[Bob Coleman]

Thanks for the input, Peter and Doug. I'll be using batts, so I guess I'll see how getting the insulation into that corner goes.

One quick follow-up: What do you mean by baffles and chutes in the bays? I have soffit vents and peak vents and I'm planning to leave the gaps above the wall blocking open to allow air flow. Do I need to do anything else?

Thanks again.

[Peter Rawlings]

One quick follow-up: What do you mean by baffles and chutes in the bays? I have soffit vents and peak vents and I'm planning to leave the gaps above the wall blocking open to allow air flow. Do I need to do anything else?


Bob, you want to leave a clear path for venting and not block with your batts for two reasons. Convective air flow from eve to peak, also airflow through insulation renders reduced R value. Pics worth a thousand words,


http://www.southface.org/web/resources&services/publications/factsheets/25_insulateceilings_4pdf.pdf

[Ed Griner]

Bob, My shop is a recycled 120yrs.old train station,with visible space in the walls and the floor.Roughed in the whole bldg and had it foamed including 10"in the floor.Its as tight as a drum,heats very easy(left the steel frame windows in for historical purposes,so it leaks just enough) and allows me to apply finishes even when its 10 degrees F out.To save money,buddied with a neighbor,had his cellar done and we both got a nice break on the price.


Good Luck/Ed

[Bob Winkler]

Bob, My shop is a recycled 120yrs.old train station,with visible space in the walls and the floor.Roughed in the whole bldg and had it foamed including 10"in the floor.

Ed, I am also looking at sprayed on foam. Can you tell me what type you used?

Bob

[Ed Griner]

Hi, The foam I used was Icy-ne-ne.Their were three adds in the yellow pages.Make sure you check them out!!! When I ask to look at some of their work only one would agree to it.There are other types of foam available,some water based. I have wooden floor,after foaming got it sanded,this stuff really hangs on. I would do all again,its great stuff. The one that showed me his work got the job. Ed



PS:This product has overspray that why i sanded the floor after.eg

[Joe Wiliams]

Thanks for the input, Peter and Doug. I'll be using batts, so I guess I'll see how getting the insulation into that corner goes.

One quick follow-up: What do you mean by baffles and chutes in the bays? I have soffit vents and peak vents and I'm planning to leave the gaps above the wall blocking open to allow air flow. Do I need to do anything else?

Thanks again.

Here's an example of baffles/chutes...

http://www.homedepot.com/Building-Materials-Insulation-Accessories/h_d1/N-5yc1vZ1xhiZbmgs/R-100537404/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

[Tom Godley]

ED - Would you PM with the name of the people you used. I used a closed cell system on my last project but I did get one estimate from ICY -- but they were a little difficult.

I would like to get an open cell estimate for an upcoming project