The R-value of closed-cell foam is a popular choice for contractors who need to insulate beneath slabs, ceilings, walls and roofs. It provides an excellent air barrier, resists moisture and retards steam. Open-cell spray foam has an R-value of approximately R-3.7 per inch, while closed-cell spray foam has an R-value that can be as high as R-6.5 per inch. The R-values are additive, so you can multiply the number of inches of insulation thickness by the R-value to get a total insulation value.
Closed-cell aerosol foams weigh between 2 and 4 pounds and have an R-value of 6.0-8.0 per inch of insulation, about twice as much as open-cell foams. When it comes to spray foam insulation, the R-value doesn't mean the same thing as it does for cellulose or fiberglass. Insulating a roof covering with R-20 spray foam exceeds the performance of the R-38 so much, that even in climatic zones where R-49 is required, it also exceeds the performance factor in those areas. There is not much difference in the R-value of the entire wall between a wall insulated with open-cell spray foam and one insulated with closed-cell spray foam.
Closed-cell spray foam has the advantage of not requiring a vapor and moisture barrier and, in addition, it has a very high R-value, making it the ideal choice for insulating basements (and both on the first and second floors). This is because heat takes longer to transfer through closed-cell spray foam due to its denser composition. Mentioning a poor application of spray foam has nothing to do with the exceptional performance of correctly used spray foams. Fiberglass and cellulose only work to prevent conduction, while spray foam acts to stop conduction and convection, or air movement.
The R-value of spray foam insulation may vary by product, manufacturer, and other variables. In a nutshell, R-Value is how professionals and customers compare apples to apples when deciding which foam is right for them. Therefore, if you install a closed-cell foam insulator with a high R-value per inch between the posts, you don't really get the full value of the investment. Before deciding to install spray foam, check with your installer to confirm the product's R-value.
If you're looking for a durable, energy efficient solution for your metal building, spray foam insulation may be the answer you've been looking for. If you're interested in installing spray foam insulation in your home, check out this short guide on how to understand the R-values of spray foam insulation. Knowing what kind of insulation you need and what its R-value is can help you make an informed decision about which type of insulation is best for your home or business.
