98995.1
I’m in a short half story (6’4″tall for the four center feet then sloping at 22º +/- to the 3’6″ knee wall). The location is the finger lakes area of New York, cold climate. The rafters are 4×4 (no ridge circa 1900). I’ve installed 2″ TUFF-R rigid foam, foil both sides, with airspace above and below. I’ll fill accessible gaps with expanding foam. QUESTION 1: Should I caulk the edges were I can’t insert the tip of the foam dispenser? QUESTION 2: what is the minimum thickness worth applying to break up thermal bridging through the rafters? Keep in mind that the room is small and short, every 1/4 inch counts! QUESTION 3: Having just spent the time sealing all gaps at the main insulation; is it worth applying a full surface of thin insulation under the drywall vs a strip on the rafter’s edge?
I eagerly await your responses! (except, of course, those of you who want to tell me I should rip it out, rebuild the roof, install exterior insulation, foam in the entire air cavity, use SIPs, tear the house down…..)
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I'd be surprised if your rafters will be straight enough to put dry wall on. If you find that to be the case, strap them with 1x stock and then foam between the strapping. Dont put foam between framing and drywall, the cushion will cause nail pops.
The rafters are sistered and drywall ready. I'll be screwing the drywall on so nail pops are a non-issue. It's really insulation value that is the heart of my question.
Nails or screws, doesn't matter. Just make sure your drywall is directly against framing. Any cushion type material will promote pops.
I routinely install foamboard over studs, held in place with horizontal strapping...never had a screw pop.I do use plenty of PL300 and screws. I also make the 1x3 stock I use from 3/4" plywood. Plywood straping is more dimensionally stable than most framing so it may be less prone to pops.
yeah thats good , I just mean keep drywall in direct contact with wood , not over a compressible foam. Strapping, framing , doesn't matter. Rich
I have a similar roof detail ( 1800's log home, 4'' Dia cedar rafters and 4x4 split ash as well) what I did was sister a 2x6 first. Then infill with 1" thick foil/fiberglass duct board ( free) then 2" foamular pink insul, then 2 more inches..it all squeezes into the bay.
Then foil/bubble/foil stuff stapled and taped to seal it all in..BTW ths is anon vented steel roof. Then 1x3 strapping and a layer of 3/4" foam between the strapping. Then sheetrock and or T&G panneling.
Maybe a R30, but the point is air sealing and some reflectivity.
That's all I got for ya..foaming the edges can't hurt, but I skipped it except for where the gaps were extreme.
Spheramid Enterprises Architectural Woodworks
"Success is not spontaneous combustion, you have to set yourself on Fire"
Thanks, I did sister and add rafters (spacing was 32" to 38" oc). I tapered them from 4" at the knee wall to 8" at the ridge.
I left 2 airspaces (roof side and interior): interior for winter heat in, exterior for summer heat out. That's a done deal.
I would think the 2" of foam and air sealing would make condensation a non issue?
So, bubble or closed cell foam over the whole interior?
Bubble wrap is a waste of money for insulation in most cases
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Yeah, but it shure looks cool, esp when its free..Same guy that gets me the duct board, can get rolls of that from where he works. That and taping it with the foil tape has made a difference here at least.Spheramid Enterprises Architectural Woodworks
"Success is not spontaneous combustion, you have to set yourself on Fire"