I am insulating the ceiling of a tuck-under garage as well as running new circuits to my garage. I’ve read this article but I have a few questions. I am in southern NH climate zone 5/6. https://www.finehomebuilding.com/2012/03/08/how-to-insulate-a-cold-floor
1. Can I use polyiso insulation here? I know the perm rating is much lower than EPS. Do I need to be worried about moisture getting trapped?
2. The rigid foam layer (if properly detailed) is the air control layer right? So I don’t need to worry about making the drywall air tight?
3. Does anyone have good examples of air sealing electrical penetrations through a rigid foam layer?
Replies
Yes, using polyiso insulation is suitable for your climate zone, but ensure proper vapor barrier installation to manage moisture.
Correct, a well-detailed rigid foam layer can act as an air control layer, but it's still wise to address any drywall gaps for added air tightness.
For air sealing electrical penetrations through rigid foam, use fire-rated sealants or gaskets, following local building codes or expert advice for specific product recommendations.