Spray Foam Roof Insulation R Value

Closed cell foam can also add to the structural strength of the roof system which can make it a more appealing choice in locations that frequently endure high winds.

Spray foam roof insulation r value.

R values are additive so you can multiple the number of inches of insulation thickness times the r value to arrive at a total insulation value. It has a lower r value per inch than closed cell foam and is vapor permeable. Closed cell spray foam r values. The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13.

R value is a measure of insulation s ability to resist heat traveling through it. The higher the r value the better the thermal performance of the insulation. 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. Having an r value in the neighborhood of r 7 per inch and the ability for some products to be applied 5 inches at once high r value applications are easily achieved.

A typical 2 4 stud filled with open cell spray foam will have an r value. For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. For 6 inches r 15 or r 19 etc.

Traditional insulation such as cellulose or fiberglass is not comparable to spray foam insulation in r value as those insulation methods use r value of heat transfer. Since closed cell foam has a higher r value per inch installers generally spray 2 in walls and 3 in rooflines to meet the energy code requirements of r 13 and r 19 respectively. Open cell spray foams are between 5 and 1 lbs per cubic foot and have an r value of 3 0 4 0 per inch of insulation. 8 3 4 4 8 2 20.

I m not going to dive into the energy code here but these numbers apply to many climate zones the latter being allowed under the ua tradeoffs rule. Corrosion problems when in contact with steel roofing moisture. For example closed cell spray foam depending on brand can offer an r 6 or r 7 per inch. Insulation level are specified by r value.

Closed cell spray foam has a far better r value per inch than other less effective insulations like cellulose fiberglass or even open cell foam. R 0 77 30 phenolic foam insulation r values. 4 8 7 21. Open cell spray foam insulation is air impermeable and is applied with a minimum of 3 5 on average and can be used for attics interior floors walls and soundproofing.

Closed cell spray foam insulation. Very good air bypass leak sealing properties. 4 5 21. Why spray foam insulation is so effective in meeting code requirements is that it has a higher r value per inch of product used than batts.

However there are open cell spray foam insulation products actually offer r 3 7 per inch such as icynene classic and. The table below shows what levels of insulation are cost effective for different climates and.