Foam Vs. Foil Home Insulation

Foam

• Foam insulation is usually applied as a "spot" insulation material in homes, to prevent drafts of air from seeping through crevices and cracks in walls and ceilings. For example, you might use foam in homes around ductwork for HVAC pipes or around electrical work to keep out drafts of cold air. Spray-on foam is often used for residential applications, while expandable foam and foam boards are used for commercial and industrial insulation, more than they are inside homes. Because you can spray it, foam is good for tight areas like corners. Because it dries it adheres permanently and does not move or shift like loose insulation materials that you blow in.

Foil

• Foil is an effective insulation material because it can both radiate heat in the winter and reflect heat in the summer. Foil used for insulation has aluminum on two sides. This allows the insulation to keep heat out in the summer, by directing it back outside, and to keep heat in during the winter, by radiating heat to inside areas. As a result, your furnace and HVAC system operate more efficiently and you save money on energy.

Similarities

• Foil and foam are supplementary types of insulation and not typically used as the main or sole type of insulation for homes. They are combined with other types of insulation such as batt blankets of fiberglass, mineral wool or blow-in cellulose, which are used as the main insulation. Foil and foam are also applied first. Foil is attached to rafters and joists or the ceiling of an attic, and foam is sprayed into cracks and crevices. After that, the main insulation is installed on floors, walls and ceilings.

Differences

• Foil and foam are distinctively different in how they look, how they are applied, efficiency ratings and how they function. Foil is designed to reflect heat back outside or radiate heat inside. Foam's job is to block air from seeping through cracks or crevices. Foams are liquids that are sprayed on and allowed to dry. Foil insulation is a sheet material that comes in rolls, so you can cut and staple the foil to surfaces. Foam and foil also differ in their R-value ratings in terms of efficiency. Foil has an R-value rating of 7.0 and spray-on foam has an R-value rating of 5.9.