Residing a small addition with vinyl and after a lot of research including FHB #181 I have a question about using rigid foam insulation and Tyvek.
I am stripping the old siding off, replacing doors and windows and then my plan was to wrap in Tyvek. Interior is already insulated (R13), this isn’t really about gaining any R value. After that I was going to wrap all window, door and fascia trim in aluminum with proper over lap flashing. Normally I would then begin to side but I want to add 1/4″ rigid insulation (typical siding fanfold siding stuff) to fur out everthing to make a lot of my transitions easier. My question is – am I creating a bad situation with vapor barriers? Should I just scrap the insulation? My research online yielded about 50% each way being the absolute correct way
Thanks in advance, Chuck
Replies
1/4" rigid "insulation" is typically perforated to eliminate any vapor retention problems it might cause (and about half it's meager insulation ability). Its only valid use is to provide a flat surface when residing over existing siding -- you don't need it.
Better to just do a very good job with the house wrap, carefully taping all joints and around windows/doors, to provide an infiltration barrier. (Note that house wrap does not comprise a vapor barrier.) Cutting down infiltration vastly improves the effectiveness of existing fiberglass insulation.
You say this really isnt about insulation,but why not? If it were mine I would consider
adding 1" pink or blue foam ....since you are replacing all the doors and windows
anyway, the trim is no big deal plus it would add R5 to your R13 wall.
Cost is not that much for a small addition.