Spray Foam Insulation
Spray polyurethane foam forms into insulation and an air barrier on roofs, walls, and other surfaces. SPF insulation is best known for its heat transfer resistance and for its effectiveness at reducing air infiltration. Air infiltration is responsible for up to 40% of a building's energy loss. Spray foam seals all the gaps, holes, and air leaks that make your energy bills unnecessarily high.
There are two types of spray foam insulation (Open cell and Closed cell). Although their main purpose is to insulate, the job the foam will do once it is sprayed on a surface is different. That is because closed cell spray foam is a much denser material. Open cell spray foam usually has a density of .5 pounds per cubic foot, compared to 1.75 pounds per cubic foot or more that closed cell has. One is not necessarily better than the other, but understanding the differences between the two will help choosing the one that meets your needs.
Open-cell spray foam is a half pound density, non structural, spray-applied thermal insulation. It is used in wall cavities, ceiling and floor assemblies, and attic applications. Open Cell Spray Foam yields an R-value of 3.5-3.7 per inch. This insulation expands into hard to reach places, and not only does it insulate but it can also help soundproof homes.
Closed-cell spray foam is one of the most efficient insulation materials. Just like Open-cell, it is a spray-applied thermal insulation but has an R value of almost 7.0 per inch. When applied, it expands to about 1 inch. For that reason this insulation is perfect for places where there is not enough space to get the desired r-value. It is also ideal to use in places where moisture is a problem as it acts as a vapor barrier.
Here in Middle Tennessee, we recommend spraying 5.5" of open cell on roof decks and 3.5" of open cell on walls. Even when codes ask for a much higher R-value than what you will technically get with just 5.5 or 3.5 inches. It is not to make sales or deceive our clients. All of our jobs have passed inspection with a lesser R-value than required because inspectors understand how efficient spray foam insulation is compared to any other insulation on the market. If you analyze the chart above you can see that doing more than 5.5" will only give you about a 3% difference in heat flow reduction. Something we definitely do not recommend is doing more than 8" of open cell because after 8" you will not get any more real benefits when it comes to insulation.