By Betty Stephens
Insulation forms a thermal blanket around your home, saving money and improving comfort. The maximum thermal performance or R-value of insulation is very dependent on proper installation. Homeowners can install some types of insulation notably blankets and materials that can be poured in place. Other types require professional installation.
When insulating your home, you can choose from many types of insulation. To choose the best type of insulation, you should first determine the following:
• Where you want or need to install/add insulation.
• The recommended R-values for areas you want to insulate.
Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and its density. In calculating the R-value of a multi-layered installation, the R-values of the individual layers are added.
Types of Insulation
There are four basic types of insulation out there: bats/blankets, spray foam, loose fill and rigid board. The most appropriate kind to use is going to depend on where you're installing insulation. Different kinds of construction and the extent of rehabilitation will affect what you need, as will code requirements. While pink blanket insulation is the most familiar, you should remember that there are a lot of other options.
This type of insulation is made up of a loose pellet or fiber mix, and is blown into the building using special types of equipment. It can be synthetic, or made of a natural material like recycled cotton and wool from the fiber industries. Benefits of this kind of insulation include easier filling of small spaces and better sound insulation. However, it's also costlier and can get everywhere. The most common type is cellulose fiber, chemically treated to prevent rot and fire dangers. Make sure the material meets regulations in your areas. There are also fiberglass and rock wool loose fill insulation, which are blown into the open stud cavities. Generally, loose fill types of insulation have R values of about R-3 to R-4 per inch of depth, while cellulose has about thirty percent more insulating value than a rock wool variety.
Blankets and Batts
These are the least expensive types of insulation and probably the most common if you're installing insulation at home. Made either from processed fiberglass or rock wool, they're used to insulate the areas above ceilings, below floors, and inside walls. Carefully installing this insulation is important if you want it to work effectively. This is a type that's best for standard stud, joist, and rafter spacings, since it's cut in widths that securely fit between the members. Some have radiant barrier backing, while other brands are merely backed with paper. Batts are usually four to eight feet long, while blankets come in long rolls that are cut to fit. R values for this kind of insulation are about R-3 per inch in thickness.
Usually made from polyurethane, fiberglass or polystyrene, this substance comes in many thicknesses and has an extremely high insulating value of about R-4 to R-8 per inch of thickness. This type of insulation is commonly used for reproofing work on flat roofs, as perimeter insulation at the edges of concrete slabs, and in basement walls. It may also be used to provide insulation in cathedral ceilings.
When used in interior installations, it has to be covered with a building code approved material, such as half inch gypsum board, to achieve the desired amount of fire safety. When installing insulation of this type outside, you'll need to cover it in a weather proof facing that meets your local codes.
This type of insulation comes as a two part liquid - the polymer and the foaming agent. Usually, the polymer in this case is a modified urethane, or a polyurethane. This liquid is sprayed into the cavities in walls, ceilings and floors, and expands during application, becoming a solid plastic filled with lots of tiny air filled cells. This makes it easy to fill unusual spaces. Installing installation of this type must be done by a professional with dedicated equipment for mixing, measuring, and spraying. This insulation is commonly in use in retrofits, since it works well for oddly shaped areas and can be installed around obstructions.
This type of insulation costs more than a traditional batt insulation, but can be cost effective anyway. This is because it forms an air barrier and an insulation, eliminating the need for caulking, taping joints, applying house wrap or vapor barrier, and other detailing.
The maximum thermal performance or R-value of insulation is very dependent on proper installation. Homeowners can install some types of insulation -- notably blankets and materials that can be poured in place. Other types require professional installation.
When hiring a professional certified installer:
• Obtain written cost estimates from several contractors for the R-value you need, and don't be surprised if quoted prices for a given R-value installation vary by more than a factor of two.
• Ask contractors about their air-sealing services and costs as well, because it’s a good idea to seal air leaks before installing insulation.
Follow this link to view the Department of Energy tips and advice web site on insulation. Department of Energy Insulation link.