The use of insulating foam is growing in popularity owing to its ease of installation in pitched and cathedral roofs as well as in framed walls and because it fills cracks and other hard-to-access spaces. Many prefer wet-blown cellulose foam to polyurethane foam because it is cheaper and has sound-proofing attributes. Polyurethane foams are more efficient but are criticized for their purported release of fluorocarbons into the atmosphere.
Foam insulation is blown into floors, walls and ceilings using special equipment. This is ordinarily done by professionals, making it more expensive than insulation that comes in strips or battens installed by carpenters.
When comparing the efficiency of different types of foam insulation, pay attention to the R value. This is a measure of the resistance to heat and cold provided by the insulation. The larger the number, the more efficient the insulation.
Cellulose foam insulation is made from recycled newspaper that is wet-bound and blasted into open wall cavities between studs and joists. Wet-blown cellulose foam is densely packed. The fibers knit together over time, stopping air and deadening sound. A wet-spray cellulose foam that is allowed to dry properly gives an R rating of about 3.4 per square inch. Boron or other chemicals are added to repel insects and act as a fire retardant; boron is preferred. Wet-blown cellulose foam should be allowed to dry completely to prevent the growth of fungi and mildew.
Polyurethane foam expands to fill voids and cracks, forming a tight barrier in floors, walls, ceilings and attics. It provides higher R values than cellulose foam, often 3.6 and higher. R ratings of 6 to 7 have been reported. It is impervious to moisture and reduces pollen and dust allergens.
Polyurethane insulating foams contain CFS (chlorofluorocarbons) and HCFS (hydro chlorofluorocarbons) that release chlorines into the atmosphere, allegedly contributing to the depletion of the ozone layer. As polyurethane foam releases CFS and HCFS, these gases are replaced by air, reducing the R rating of the insulation.
The amount of fluorocarbons released and their danger to the environment is a matter of contentious debate between manufacturers and the Environmental Protection Agency, which has been conducting ongoing tests of polyurethane foam.
A thicker layer of foam generally increases the R value.
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