Spray Foam R Value Required On Attic

When determining how much insulation you need don t guesstimate calculate.

Spray foam r value required on attic.

The r value of some insulations also depends on temperature aging and moisture accumulation. The higher the r value the greater the insulation performance. Closed cell spray foam insulation. This is very important in situations where your code requires an r 21 for the wall but you only have a 2 4 stud because closed cell spray foam is the only way you would achieve the required r value to meet code.

Installing more insulation in your home increases the r value and the resistance to heat flow. Recommended home insulation r values. When calculating the r value of a multilayered installation add the r values of the individual layers. 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.

R value measures how well certain building insulation materials can resist heat. R value is a measure of insulation s ability to resist heat traveling through it. It has a lower r value per inch than closed cell foam and is vapor permeable. The higher the r value the better the thermal performance of the insulation.

Focusing on spray foam insulation materials there is a difference between the two main types. Intumescent coatings are not always needed to coat spray foam in the attic in order to meet code thermal barrier requirements. Insulation level are specified by r value. Know exactly how much you need with our project calculators.

The r value of fiberglass insulation is approximately 2 2 per inch so much thicker fiberglass insulation is required to achieve the same r value of 38. 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. The r value of spray foam insulation is approximately 6 per inch so those using spray foam as their insulator will need about 6 3 inches of thickness to reach r 38.

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. 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. That means if you used foam it green closed cell which is r 7 per inch it s r value for a 3 5 deep wall cavity would be r 24 5. However there are open cell spray foam insulation products actually offer r 3 7 per inch such as icynene classic and.