Spray Foam Roof Insulation R Value

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.

Spray foam roof insulation r value.

Closed cell spray foam insulation. A typical 2 4 stud filled with open cell spray foam will have an r value. A spray foam roofing system has an r value of 6 6 per sq. 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.

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. Focusing on spray foam insulation materials there is a difference between the two main types. The higher the r value the better the thermal performance of the insulation. For 6 inches r 15 or r 19 etc.

Insulation level are specified by r value. 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. These r values are a sum meaning this should be the total r value once you add up the entire depth 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.

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 r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13. 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.

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. Closed cell spray foam r values. The table below shows what levels of insulation are cost effective for different climates and. 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.

Recommended home insulation r values. 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. It has a lower r value per inch than closed cell foam and is vapor permeable. Most of the time spray foam can be directly applied to existing roofing systems but in some cases a polyiso board is needed.

Install a spray foam roofing system. However there are open cell spray foam insulation products actually offer r 3 7 per inch such as icynene classic and. 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.