Why is foam insulation not recommended for use between studs in the wall?
Frank writes from Gaithersburg, Maryland: “I recently observed a neighbor doing some remodeling in his house. His choice of insulation was Foamular Pink XPS, which he carefully cut and fit between the studs, caulking around the edges for air sealing. He used 2 layers – 2″, and 1.5″, filling out the 3.5” stud cavity. Doing my math this adds up to an R-Value of 17.5, which is much better than the R-11 one would get with fiberglass. I had never seen this before so I decided to search on the net about this, and all I could find was that it “Is not recommended,” but no information on why. Can you comment on using this product in this manner? If it is not recommended, can you explain why?” Answer: Owens Corning manufactures FOAMULAR® rigid foam insulation as insulation sheathing. The company also makes FIBERGLAS™ insulation batts that can achieve a R-15 at 3.5 inches, which meets building codes. If the foam product is used as you describe, additional labor is needed that can be avoided with
