Information for Home Insulation
Insulation is a building material used to prevent air transfer and heat loss through the walls and roof of the home. Proper insulation can have a number of benefits for homeowners, including lower energy bills, more comfortable houses, and a reduced level of environmentally-harmful emissions. According to the U.S. Energy Star program, homeowners who insulate their homes according to Energy Star guidelines can save 20 percent on heating and cooling costs each year.
R-Value
The ability of a material to resist heat flow is known as "R-value." The higher the R-value of an insulating material, the more effective it will be at providing thermal resistance through exterior walls. R-value is generally measured in terms of thermal resistance per inch of material use. For instance, 1 inch of rigid foam insulation has an R-value ranging between 4 and 6, while 1 inch of batt insulation has an R-value of between 1 and 2. Different types of insulation can be combined to achieve the desired thermal resistance rating.
Wall Insulation
Most wall insulation is installed as the walls are built. This means that the insulation is placed between the wall framing and exterior sheathing or siding. This type of installation offers the most flexibility for choosing materials. For new construction, homeowners may choose fiberglass batts or rigid foam boards. While fiberglass or cotton batts are generally the more economical option, they provide less thermal resistance per inch than rigid foam boards made from urethane or polystyrene. In addition, rigid foam tends to cover the entire wall cavity more completely and result in fewer air leaks.
Attic and Roof Insulation
Because of the amount of direct sun exposure they are in contact with, roofs and attics tend to require high levels of insulation. Often, attics and crawlspaces are insulated using loose-fill materials, such as rock wool or cellulose. These products are blown into difficult to access areas and are relatively affordable. Because they are loosely filled, however, they tend to provide low R-values, even when large quantities of material are used. When insulating roofs, rigid panels may be attached directly to the framing system, or may be installed over the interior surface of the roof itself.
Spray Foam
To insulate an existing home, the most popular option is spray foam. This material is made starts as a liquid and is made from polyurethane or polystyrene. It is sprayed into small holes, which are drilled into the walls by professional installers. Once sprayed, the foam expands to fill the entire wall cavity. It can act as a means of structural support for the home's framing, as it becomes rigid and will not sag. Spray foam is one of the most effective types of insulation because it allows for few gaps that air can pass through.
Structural Insulated Products
Several new structural insulated products are gaining popularity with homeowners, especially those concerned with green building technology. Structural Insulated Panels (SIPs) are made of sheets of OSB sandwiched around layers of rigid foam insulation. SIPs take the place of traditional framing and sheathing systems and offer superior insulating properties. Another product, insulated concrete forms (ICFs) is used to construct foundations and basement walls and floors. Traditional concrete is poured into these forms, which contain integral foam insulation. The forms are then left in place and help to prevent cold air from entering the home.
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