Closed Cell Spray Foam With 1 5 Mineral Wool In Attic

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

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

Open cell spray foam r values. In this case the typical expense of spray foam insulation installation is 2 128. Open cell spray foam typically has an r value of 3 5 per inch and it should be noted that open cell does not form a tight air seal. It can be used between wood framed walls and in the attic floor.

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. 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. Spray foam insulation is available in open cell and closed cell. Open cell spray foam costs typically 0 25 to 0 50 per board foot and closed cell spray foam ranges from 0 90 to 1 50 per board foot.

The main drawback is high cost. 1 5 mineral fiber insulation. 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. It ties with rock wool batts for an stc of 50 in a laboratory test environment.

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. Spray foam with air. But the spray foam is still exposed to the attic and needs an ignition barrier. Mineral stone wool insulation batts are slightly better insulators than the off the shelf fiberglass batts sold at most lumberyards and home centers.

Two types of spray foam insulation exist namely open cell and closed cell. The foam must be thick enough to meet minimum code requirements. First spray foam has the best stc rating of all the options. Most ceilings are made of 1 2 drywall.

Oregon shepard add boric acid sodium pentaborate dehydrate and a proprietary component that includes a natural protein last i checked with them. It performs much better than any form of batt for stopping air flow but it is not as complete of an air seal as closed cell spray foam. In this case you have a choice of several prescriptive materials approved by the code as ignition barriers. Black mountain natuwool which is 95 wool with 5 polyester binder and is treated with borax.

However in real construction a batt would be cut to fit around utilities and boxes leaving sound transfer cracks.