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.

With high yield and excellent adhesion it s an. Spray foam insulation is available in open cell and closed cell. 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. If you want to install spray foam in a stud wall and price is no object then it would seem to make sense to specify closed cell spray foam right.

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. Mineral stone wool insulation batts are slightly better insulators than the off the shelf fiberglass batts sold at most lumberyards and home centers. Multiple immediate passes with no wait time may also be applied. Open cell foam is soft and spongy impermeable to air but permeable to moisture and according to the doe has an r value per inch ranging from r 3 6 to r 4 3.

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. 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. 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. There are two main types of spray foam.

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. In these humid attics the moisture is getting through the open cell spray foam by vapor diffusion not via air leakage. 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. 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.

Open cell and closed cell each with different characteristics. 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.