Spray Foam R Value Required On Attic

R value measures how well certain building insulation materials can resist heat.

Spray foam r value required on attic.

Normally in occupied areas all spray foam must be covered by a 15 minute thermal barrier such as thick drywall per code requirements in irc section 316 4 and ibc section 2603 4. However there are open cell spray foam insulation products actually offer r 3 7 per inch such as icynene classic and. The higher the r value the better the thermal performance of the insulation. It has a lower r value per inch than closed cell foam and is vapor permeable.

Know exactly how much you need with our project calculators. A typical 2 4 stud filled with open cell spray foam will have an r value between 10 5 and 14. When determining how much insulation you need don t guesstimate calculate. Focusing on spray foam insulation materials there is a difference between the two main types.

Recommended home insulation r values. 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. Closed cell spray foam insulation. 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 higher the r value the greater the insulation performance. 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. The r value of some insulations also depends on temperature aging and moisture accumulation. R value is a measure of insulation s ability to resist heat traveling through it.

Insulation level are specified by r value. Installing more insulation in your home increases the r value and the resistance to heat flow. 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. 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.

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