Generally speaking the rule of thumb is the higher the R-value, the greater the insulating power. Focusing on spray foam insulation materials, there is a difference between the two main types. According to industry publication, Fine Home Building , the R-value for open-cell spray foam is between R-3.5 – R-3.6 per inch.
Also, which is better open or closed cell foam insulation? Closed cell foam has a higher R-value than open cell foam, usually about 6.0 per inch. This higher rating makes closed cell foam better at keeping heat in or out of a structure. Open cell foams have an R-value of around 3.5 per inch.
Additionally, how many inches of closed cell foam do I need?
Now generically speaking, we usually recommend open cell spray foam to be 6-inches on a roof deck or ceiling and 3-inches in the walls. Closed cell spray foam should be 4- to 5- inches on the ceiling and 2- to 3-inches in the walls.
What is the R value of 2 inches of spray foam?
Open-cell spray foam absorbs and holds water. It has a lower R-value per inch than closed-cell foam and is vapor-permeable. The R-value is R-3.5 to R-3.6 per inch, so filling a 2×4 cavity yields about an R-13.