I need to insulate and seal some cantilevered overhang areas on my house and am wondering about the best way to do it considering performance and cost. Fiberglass batt was originally installed above soffit board and in between the joists with no air sealing. When you pull the soffit board you can see evidence of air infiltration by way of the dirt-stained fiberglass insulation. I plan to remove the fiberglass (maybe) and install some sort of foam.
I'm sure spray foam would be the best in performance but its a small area and bringing in a contractor would be expensive. I've priced out DIY foams kits but the price seems outrageous, roughly 4x that of sheet foam. I put together a spreadsheet with R values, costs of materials, etc. and found that sheet goods provide much more value if you compare how much volume per dollar you get while taking into account R values per inch thickness.
My question: does anyone see any problem with using sheet foam to fill the joists bays in successive layers while using canned spray foam to seal the installation?
I may even put in a few layers of foam and then fill the remaining bay space with some of the fiberglass that I've removed.
Alternatively, I could pull the original fiberglass down temporarily, seal the seams above it, reinstall the fiberglass and then install foam board below it, in between joists, sealing the gaps with spray foam or caulk. I'd then replace the soffit board. (As of actually typing this post I'm now liking this option the best).
I'm sure spray foam would be the best in performance but its a small area and bringing in a contractor would be expensive. I've priced out DIY foams kits but the price seems outrageous, roughly 4x that of sheet foam. I put together a spreadsheet with R values, costs of materials, etc. and found that sheet goods provide much more value if you compare how much volume per dollar you get while taking into account R values per inch thickness.
My question: does anyone see any problem with using sheet foam to fill the joists bays in successive layers while using canned spray foam to seal the installation?
I may even put in a few layers of foam and then fill the remaining bay space with some of the fiberglass that I've removed.
Alternatively, I could pull the original fiberglass down temporarily, seal the seams above it, reinstall the fiberglass and then install foam board below it, in between joists, sealing the gaps with spray foam or caulk. I'd then replace the soffit board. (As of actually typing this post I'm now liking this option the best).