Closed Cell Spray Foam With 1 5 Mineral Wool In Attic

Insulating value and strength.

Closed cell spray foam with 1 5 mineral wool in attic.

Johns manville corbond iii closed cell spray polyurethane foam insulation offers and r value of r 7 per inch and can be applied in a single pass to a maximum of 3 5 inches providing superior thermal performance with seamless air sealing and moisture control in a single step. The r value of open cell spray foam is about 3 5 per inch although the r value can be different depending on the product. This is very important in situations where your code requires an r 21 for the wall but you only have a 2 4 stud because closed cell spray foam is the only way you would achieve the required r value to meet code. The inch of foam filling the gap between the courses of stud can be done more cheaply and uniformly using rigid polyisocycanurate and is higher.

As i noted in a different article air leakage through spray polyurethane foam open cell spray foam only needs to be 3 or 3 5 inches thick to form a decent air barrier. A full 2 5 of fluff or half pound open cell foam which would fully seal everything in the 2x3s will be substantially higher performance and costs about the same as an inch of closed cell foam. Mineral stone wool insulation batts are slightly better insulators than the off the shelf fiberglass batts sold at most lumberyards and home centers. Mineral wool batts for 2 4 walls have an r value of 15 while a standard fiberglass batt made to fit in a 2 4 wall has an r value of 11 or 13.

There are two main types of spray foam. Multiple immediate passes with no wait time may also be applied. In these humid attics the moisture is getting through the open cell spray foam by vapor diffusion not via air leakage. Open cell spray foam has a low density and is many times applied in interior walls and areas that are hard to reach in a home.

Open cell and closed cell each with different characteristics. With high yield and excellent adhesion it s an. Open cell foam has an r value of about 3 5 to 3 7 per inch while closed cell foam has an r value of about 6 per inch. Once applied closed cell foams become rigid and have an r value range from r 6 to.

Open cell spray foam has an r value of about r 3 7 per inch while closed cell spray foam has an r value that may be as high as r 6 5 per inch. That means if you used foam it green closed cell which is r 7 per inch it s r value for a 3 5 deep wall cavity would be r 24 5.