Why Not Spray Foam In My Attic?
Sprayed foam insulation, often referred to by the commercial name Icynene®, is often touted as a superior solution to insulating homes. While it has many good qualities, we do not recommend its use. This note provides some insight as to why you should carefully consider all factors before purchasing Icynene-like products.
What Is Sprayed-Foam?
Sprayed-foam is a chemical product, similar to polyurethane, that is sprayed like paint using equipment much like that used by professional painters. When applying the product, the worker must wear protective clothing and a full-face respirator to ward off the toxic fumes. Initially, the chemical goes on like paint but rapidly expands, filling nooks and crannies. The insulating capability of sprayed foams comes from the air trapped in cells - bubbles - created during expansion, and from the material itself. Icynene is an “open-cell” foam, meaning that the cells that are created are not completely enclosed — like a sponge; other foams are “closed-cell” products, where the cells are completely enclosed bubbles.
The foam is usually applied to the underside of the roof rafters, just under the roof decking, and along any vertical walls in the attic. This forms a relatively tight air barrier, limiting air leaks, as well as providing excellent insulation values. The amount and quality of insulation is not in question.
What are the downsides?
First, you don’t live in your attic. Insulating the top and sides of the attic space will prevent heat from escaping through your roof. However, heat will still leak through your ceiling into the attic. As the heat rises, it would collect in the attic and form a warm space there that is not usable. Why should you spend your energy dollars to heat areas where you don’t spend your time?
Second, the cost of Icynene and similar products is relatively expensive. The chemical itself costs more than fiberglass, and the application process is more complicated and labor-intensive. The raw material of fiberglass is sand, one of the most common materials on earth.
Third, the chemicals that are used in the material must emit gases in order to form the bubbles or cells. The emission of these gases continues for some time after the foam is installed. Some people have unpleasant, or unhealthy reactions to these gases. Fiberglass does not emit gases.
Fourth, applying insulation to the underside of the roof decking limits the ability of the roof to shed heat generated by the sun. Normally, heated shingles radiate heat up and away from the roof, as well as down and into the attic (that’s what causes the attic to get warm.) Ventilating the roof gives the shingles a path to dump some of the heat and stay cool. Applying insulation to the back side of the shingles shuts off that cooling path, leading to hotter shingles and a reduced roof life.
Fifth, open-cell foams are like sponges and will soak up water. Any leak in your roof will be retained by the foam, and hidden from view, resulting in premature rotting of roof decking and rafters. It could also be a breeding space for mold. Fiberglass does not retain water.
For these reasons, NRG SVRS does not recommend spray foam products.
*Icynene is a registered product of the Icynene, Inc, company.
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Disclaimer: The information presented herein is provided for informational purposes only. Technical descriptions, specifications, details, requirements, and limitations expressed do not constitute an endorsement, approval, or acceptance of the subject matter by NRG SVRS. There are no warranties, either expressed or implied, regarding the accuracy or completeness of this information. Full reproduction is not permitted. ©2011,NRG SVRS, LLC.
