Closed cell spray foam insulation has an approximate R-value of 6.5 per inch. Open cell spray foam insulation has an approximate R-value of 3.6 per inch. Compared with batt and blown in insulation alternatives made from fiberglass or cellulose, spray foam insulation has a greater R-value per inch.
When you choose spray foam insulation for your project, you are getting a three-in-one solution. Spray foam acts as a thermal barrier as well as an air barrier. In the case of closed cell foam, you are also getting a moisture/vapor barrier. While the cost for spray foam insulation might be higher than other types, if you factor in the greater benefits you get from a 3-in-1 product, the cost may be more comparable to traditional forms of insulation.
Other elements to factor into your insulation equation besides the initial cost of installing spray foam insulation have to do with the long term savings you will realize and the longevity of the product. Spray foam does save more money in energy costs than other types of insulation. Over time, you pay back your initial investment in spray foam much more quickly than with traditional insulation because of the greater savings each month. Furthermore, it is good to know that spray foam is a permanent solution to insulation. When fiberglass or cellulose get wet, they lose their insulating value. Also, over time, each of these alternatives to spray foam lose their effectiveness due to settling and compression leading to the necessity of a complete removal and replacement. With foam, you have a lifetime product and most manufacturers of foam offer a limited lifetime warranty on their products if installed correctly. Few home improvements can claim an eighty-plus year useful life.
Foam is a home improvement that also has value to future buyers. A home that has been insulated properly with spray foam has lower utility bills and never needs new insulation. These are attractive features of a home for the next buyer since competing homes they might be looking at will have higher bills and the prospect of replacing insulation at some point in the future.