Each foam we are going to talk about today has a blowing agent which forms the cells and then fills them with gas. All open cell foams use water as the blowing agent and when this water is mixed with the “A” Chemical, called isocyanate, it produces carbon dioxide as the insulating gas within each little cell (Tip: Break open the foam after it’s applied to see the size of these cells). Open cell foam is affordable as the yield from a set (two 55 gallon drums) is about 16,000 board feet (Board Foot = 12″ L x 12″ W x 1″ H). The blowing consists of mainly water and the bubbles are very large.
All closed cell foams on the market today use water and some other chemical as their blowing agent and depending on what this chemical, can be very expensive. Closed cell foam produces very small bubbles (Tip: Break open the foam after it’s applied to see the size of these cells). The yield from a set of closed cell foam (two 55 gallon drums) is only 4,000 board feet.
It’s also possible to have a closed cell foam with only water as a blowing agent. But pay attention to the aged r-value of the foam – not the initial r-value – as the aged value is obtained 30 days after initial application. Always ask your contractor what the aged r-value is in writing, or through company literature. The higher your aged r-value, the better.
The typical aged r-value for closed cell foam is about r-6.2. The initial r-value is anywhere from r-6.4 to r-7.0 and is a product like soy spray foam.
A typical r-value for an open cell foam at application might be r-4.4 and the aged value might be r-3.4 which is considerably less than the closed cell foam. Because of this we don’t recommend or use open cell foam and tell people to use cellulose or batt insulation for soundproofing.
You may also hear open cell foam referred to as 1⁄2-pound foam and the closed cell foam as 2-pound foam. The higher the r-value the more insulating power the foam has, and in some cases you might only be able to spray closed cell foam in the cavity based on size and desired r-value.
For these reasons we recommend only closed cell foams at Act Green Spray Foam.
Dr. Spray Foam (Mark Gugino)