R Value Of Attic Spray Foaam

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 of attic spray foaam.

Add insulation to attic. R value is a measurement of thermal resistance and measures the ability of heat to transfer from one side of an object to another. R value measures how well certain building insulation materials can resist heat. The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13.

Two inches of closed cell foam will provide r12 r14 of insulation. Existing 3 4 inches of insulation. The r value of closed cell foam is r 6 5. 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.

Open cell spray foam typically has an r value of 3 5 per inch and it should be noted that open cell does not form a tight air seal. As a benchmark one inch of solid wood has an r value of 1. Open cell spray foam absorbs and holds water. This is because the effects of thermal bridging are limited which also results in the elimination of melt lines on the roof surface in cold climates.

Recommended insulation levels for retrofitting existing wood framed buildings. Closed cell spray foam insulation. The higher the r value the greater the insulation performance. Spray foam isn t thick enough.

This is more common with closed cell foam but it happens with open cell foam too. Closed cell spray foams are between 2 and 4 lbs. Encapsulating the rafter or top truss chord roof framing members with spray foam will improve the energy efficiency of the attic space. So let s find out what you need and discuss how you can get there effectively but also cost efficiently.

Spray foam contracts and pulls away from framing. 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. It performs much better than any form of batt for stopping air flow but it is not as complete of an air seal as closed cell spray foam. 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.

It has a lower r value per inch than closed cell foam and is vapor permeable. Wood has an r value of about one per inch of thickness. Open cell spray foam r values. How long does spray foam r value last.

When determining how much insulation you need don t guesstimate calculate. Just like for open cell foam r values are additive. They sport an r value of 6 0 8 0 per inch of insulation about double their open cell foam counterparts.