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Types of Liquid Foam Insulation
Today, most foam materials use foaming agents that don't use chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs), which are harmful to the earth's ozone layer.
There are two types of foam-in-place insulation: closed-cell and open-cell. Both are typically made with polyurethane. With closed-cell foam, the high-density cells are closed and filled with a gas that helps the foam expand to fill the spaces around it. Closed-cell foam is the most effective, with an insulation value of around R-6.2 per inch of thickness.
Open-cell foam cells are not as dense and are filled with air, which gives the insulation a spongy texture. Open-cell foam insulation value is around R-3.7 per inch of thickness.
The type of insulation you should choose depends on how you will use it and on your budget. While closed-cell foam has a greater R-value and provides stronger resistance against moisture and air leakage, the material is also much denser and is more expensive to install. Open-cell foam is lighter and less expensive but should not be used below ground level where it could absorb water. Consult a professional insulation installer to decide what type of insulation is best for you.
Available liquid foam insulation materials include:
Some less common types include Icynene foam and Tripolymer foam. Icynene foam can be either sprayed or injected, which makes it the most versatile. It also has good resistance to both air and water intrusion. Tripolymer foam—a water-soluble foam—is injected into wall cavities. It has excellent resistance to fire and air intrusion.
Liquid foam insulation -- combined with a foaming agent -- can be applied using small spray containers or in larger quantities as a pressure-sprayed (foamed-in-place) product. Both types expand and harden as the mixture cures. They also conform to the shape of the cavity, filling and sealing it thoroughly.
Slow-curing liquid foams are also available. These foams are designed to flow over obstructions before expanding and curing, and they are often used for empty wall cavities in existing buildings. There are also liquid foam materials that can be poured from a container.
Installation of most types of liquid foam insulation requires special equipment and certification and should be done by experienced installers. Following installation, an approved thermal barrier equal in fire resistance to half-inch gypsum board must cover all foam materials. Also, some building codes don't recognize sprayed foam insulation as a vapor barrier, so installation might require an additional vapor retarder.
Liquid foam insulation products and installation usually cost more than traditional batt insulation. However, liquid foam insulation has higher R-values and forms an air barrier, which can eliminate some of the other costs and tasks associated with weatherizing a home, such as caulking, applying housewrap and vapor barrier, and taping joints. When building a new home, this type of insulation can also help reduce construction time and the number of specialized contractors, which saves money.
Foam insulation is very effective in the development of a super tight building enevelope. It will stop air leakage and enable more total control of the interior living space. This present potential problems in that our living and breathing in the living space generates moisture.
Traditional building construction practices are precisely the opposite and utilizes the concept of venting in the attic and in the crawl space whereby the area above and below the living envelope allows for the eveporation of moisture.
In designing a super tight envelope that is totally sealed there should be careful thought and concern for moisture in the enclosed area. Because foam is so effective at sealing drafts, the space should be thoughtfully designed as a whole house system, with exhaust vents for all areas of the house that generate moisture, and consideration should be given to installing an Energy Recovery Vent (ERV) to normalize the humidity between exterior and interior, to avoid the potential of developing a sick hoiuse syndrome.
Open cell is advisable in attic applications where you want moisture to freely move through when a roof leak developes, to avoid major structural damage over time. Close cell is most advisable in the peremeter of the crawl space or basement area where concern is for a more dense insulation product with more structure. (I have seen it done but advise against, applying foam on the bottom side of flooring since doing so seals all of the mechanical systems into the muck and makes maintainence profoundly troublesome and wretched for the future).
Bob Windom, Windom Construction Co. Inc. Atlanta
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