Heat loss through walls, windows, roofs and basements is known to be a significant drain on heat efficiency and household budgets. Spray foam insulation is perhaps the cheapest and most effective way to retrofit an existing house for higher energy efficiency. In the long run, good insulation will save thousands of dollars every year in heating costs.
There are two main types of foam insulation: closed cell and open cell. Open cell insulation is foam that expands (up to 100 times its compressed volume) and fills with air. Closed cell insulation, on the other hand, fills with a special gas that’s already included in the spray.
Open-cell insulation is much cheaper, and very effective at blocking sound. Closed-cell insulation is more expensive, but provides improved insulation as well as excellent moisture and vapor resistance, and even rigid structural support. Depending on your budget and insulation needs, you may select either type for your home.
Heat resistance is measured numerically with a variable called the R-value, which is the ratio between temperature difference across an insulator and heat transfer per unit area. The higher the R-value, the better the insulator efficiency. Open-cell foam typically has an R-value between 3.6 and 4.5 per inch of thickness. Closed-cell insulation has an R-value between 5 and 7 per inch.
For comparison, the R-value of traditional fiberglass “batt” insulation ranges between 3.1 and 4.30 per inch.
Some builders recommend hybrid insulation – a layer of foam, covered with fiberglass batt. While an interesting idea in theory, it’s very difficult to achieve in practice, the main problem being moisture accumulation due to the different permeability properties of the two materials. This is why EcoLogics does not recommend the use of hybrid insulation – either go with 100% foam, or 100% fiberglass batt.
It’s difficult to give meaningful numerical estimates for savings, since energy costs are unpredictable and every home has different characteristics. A sample estimate prepared by EcoLogic for a home in Darien, CT has found significant energy savings, especially in winter.
The estimate was for house measuring 7,000 sq. ft., with 61,000 cubic feet of conditioned volume, and heated with natural gas, based on 2009 fuel prices. The estimate compared fiberglass insulation with open and closed-cell foam. It found that total heating and cooling costs for the house amount to:
This resulted in estimated annual savings of $3,149!
All in all, the house would end up using 44% less energy than a comparable house built to code with fiberglass insulation.
soy-based spray foam has recently gained renown and market share among people who are concerned about non-renewable resources and pollution. While supply of soy foam products is still limited, it’s increasing in response to growing consumer demand.
For any organic-based material, mold and other pests are always a concern; however, soy-based spray foam is no more susceptible than polyurethane to mold, since it provides a barrier against mold spores just as non-organic foam. Soy-based foam is also an unfriendly medium for mold growth. The main challenge with soy-based foam products is finding a brand that is true to its claims – some manufacturers resort to using a token amount of soy derived ingredients in order to claim to be environmentally friendly, even though most of their product is still made from petroleum.