Question re: rigid foam board insulation
Question: I am putting on a new 2nd story addition (removing existing attic space); exterior wall framing is 2×4, with fiberglass insulation on inside. I am considering installing 1/2 inch rigid foam board insulation (foil faced) on the exterior side of the 2x4s and then installing the 1/2 inch sheathing on top, followed by house wrap and fiber cement siding. Good idea? Bad idea? Goal: thermal break, greater sound insulation, greater insulation value (foam board has R value of 3.6. Concerns: vapor barrier in wrong location/trapping moisture, difficulting fastening sheathing/fiber cement siding. Any thoughts welcom
Replies
two things wrong with your proposal
> it takes away from shear strength in wall frame assembly by separating the sheathing from the studs.
>> the vapor bar is on the wrond side of the wall if this is in a moderate or northern climate - it belongs on the inside of the wall.
Excellence is its own reward!
Where do you live...climate-wise?