Spray Foam Roof Insulation R Value

A spray foam roofing system has an r value of 6 6 per sq.

Spray foam roof insulation r value.

Focusing on spray foam insulation materials there is a difference between the two main types. 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. 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. Closed cell spray foam insulation.

Closed cell spray foam r values. 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. A typical 2 4 stud filled with open cell spray foam will have an r value. R value is a measure of insulation s ability to resist heat traveling through it.

Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value. 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. 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. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation.

The higher the r value the better the thermal performance of the insulation. However there are open cell spray foam insulation products actually offer r 3 7 per inch such as icynene classic and. For example closed cell spray foam depending on brand can offer an r 6 or r 7 per inch. For 6 inches r 15 or r 19 etc.

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. 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. Insulation level are specified by r value.

If you install 2 inches of iso board r 11 and 3 inches of spray foam r 19 8 you ll be over an. 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 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. Most of the time spray foam can be directly applied to existing roofing systems but in some cases a polyiso board is needed.

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. Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces. Recommended home insulation r values.