Spray Foam Roof Insulation R Value

A typical 2 4 stud filled with open cell spray foam will have an r value.

Spray foam roof insulation r value.

The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13. 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. 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. If you install 2 inches of iso board r 11 and 3 inches of spray foam r 19 8 you ll be over an.

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. 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. The higher the r value the better the thermal performance of the insulation. 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.

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. For example closed cell spray foam depending on brand can offer an r 6 or r 7 per inch. Recommended home insulation r values. 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. Insulation level are specified by r value. Closed cell spray foam r values. Focusing on spray foam insulation materials there is a difference between the two main types.

However there are open cell spray foam insulation products actually offer r 3 7 per inch such as icynene classic and. 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. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. Most of the time spray foam can be directly applied to existing roofing systems but in some cases a polyiso board is needed.

It has a lower r value per inch than closed cell foam and is vapor permeable. 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. 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. The table below shows what levels of insulation are cost effective for different climates and.

For 6 inches r 15 or r 19 etc. R value is a measure of insulation s ability to resist heat traveling through it. 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.