stickshift
Well-known member
I'm going to replace the very old, worn down insulation on my attic floor, but before I install R23 5-1/2" (joist height) stone wool batts (and then I'll lay another layer of batts perpendicular that will cover the joists and mitigate thermal bridging through the joists), I want to air seal the attic floor. Had some questions for guys who have already air sealed their attic floor or looked into doing so.
What are the IRC rules regarding use of canned spray foam, around attic floor penetrations? Do I have to use fire rated spray foam for all of the air sealing, even though it's the same product as the regular spray foam but with orange dye?
For where the walls below meet the drywall ceiling, I was thinking of using caulk instead of spray foam, largely because temps are below spray foam application temps, and while I can raise localized temp for smaller applications such as wiring penetrations (as well as raise temp of spray foam can) using a heat gun, this is not practical for an entire wall-ceiling junction. Maybe an outdoor rated silicone caulk (not so much for water resistance, but for very cold temp tolerance) would be good for this?
What about chases and flues like plumbing vent pipe and kitchen exhaust pipe? Some of the holes cut into the attic floor are way oversized for these. Maybe cut a strip of aluminum sheet to fill most of the gap and then spray foam inner and outer edges to secure the alu sheet to both pipe and attic floor?
All my ceiling lights are recessed LED (no retrofits). Some are the deeper style (similar in height to older non-LED ceiling lights) while others are wafer style. Both are insulation-contact rated. I've seen people use Tenmat covers, but these are outrageously expensive (~$20 each) if you have a lot of lights. Are there commercial alternatives that are so expensive or DIY alternatives that are not very time consuming?
What about ceiling fans? How to air seal those?
What are the IRC rules regarding use of canned spray foam, around attic floor penetrations? Do I have to use fire rated spray foam for all of the air sealing, even though it's the same product as the regular spray foam but with orange dye?
For where the walls below meet the drywall ceiling, I was thinking of using caulk instead of spray foam, largely because temps are below spray foam application temps, and while I can raise localized temp for smaller applications such as wiring penetrations (as well as raise temp of spray foam can) using a heat gun, this is not practical for an entire wall-ceiling junction. Maybe an outdoor rated silicone caulk (not so much for water resistance, but for very cold temp tolerance) would be good for this?
What about chases and flues like plumbing vent pipe and kitchen exhaust pipe? Some of the holes cut into the attic floor are way oversized for these. Maybe cut a strip of aluminum sheet to fill most of the gap and then spray foam inner and outer edges to secure the alu sheet to both pipe and attic floor?
All my ceiling lights are recessed LED (no retrofits). Some are the deeper style (similar in height to older non-LED ceiling lights) while others are wafer style. Both are insulation-contact rated. I've seen people use Tenmat covers, but these are outrageously expensive (~$20 each) if you have a lot of lights. Are there commercial alternatives that are so expensive or DIY alternatives that are not very time consuming?
What about ceiling fans? How to air seal those?