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House Insulation

House insulation is a key component in maintaining a comfortable indoor environment.

House insulation is often rolled over attic floors. [©Jupiter Images, 2009]
©Jupiter Images, 2009
House insulation is often rolled over attic floors.

House Insulation

Whether to keep a house warm in the winter or cool in the summer, proper house insulation is vital to maintaining a comfortable temperature level and managing energy costs. According to the U.S. Department of Energy, 20 percent of homes built in the United States prior to 1980 are not adequately insulated, while the North American Insulation Manufacturers Association (NAIMA) estimates that 65 percent of homes in America lack sufficient insulation. Improper house insulation causes up to a 50 percent heat loss. House insulation controls heat transfer by keeping heat inside in the winter and outside during the hot summer months.

ENERGY STAR states that adding house insulation to outer walls, attics and windows is often the most effective way to decrease energy costs and increase energy efficiency, with up to a 20 percent savings in cooling and heating costs.

Insulation R-Value

House insulation is measured by R-value, which is determined by the material used, thickness and weight per square foot of installed insulation. Higher R-values provide the most insulation. Different R-values of house insulation are recommended for different areas being insulated; for instance, an R-value used for attics will not be the same as that used for basements or crawlspaces.

House Insulation Materials

House insulation is made from the following types of materials:

  • Fiberglass, made of molten glass
  • Cellulose, made from recycled paper
  • Mineral wool, made from molten rock
  • Synthetics, such as polyurethane foam or polystyrene foam


Additionally, a reflective insulation used as an exterior house wrap applied to the sheathing is becoming more common. This aluminum radiant barrier is usually made of two layers of foam or plastic bubbles. It provides protection from water penetration as well as reduces outside air penetration and blocks the loss of radiant heat.

Types of House Insulation

The four types of house insulation include:

  • Batts or blankets, which are sections of fiberglass house insulation that come ready to fit between joists or studs
  • Rolls of house insulation that are placed on top of joists, between wall studs or over attic floors
  • Loose-fill house insulation, which comes in different types of material, including fiberglass, cellulose or rock wool, and is blown into walls or attics by drilling a hole into the outer wall between studs, inserting a blower hose into the hole and administering the insulation
  • Foam boards, which are rigid and lightweight and are generally used for concrete slabs or cathedral ceilings

Insulating Doors and Windows

Weather stripping is also a type of house insulation. Gaps around doors and windows, even those less than a 1/4-inch wide, can let in as much cold air as an open window. Self-adhesive, felt or foam weatherstripping is used around doors and windows to stop drafts and air leaks.

In addition to weather stripping, heat loss through windows can also be controlled by covering windows with plastic or using insulated drapes.

Attic Insulation

Attics are one of the most important areas when it comes to house insulation. Unfortunately, many attics are not properly insulated with the recommended 12 to 18 inches of insulation. Most notably, attic access doors usually are found to lack any insulation. House insulation and weather stripping should be added to attic doors for maximum benefit.

For attics that are not insulated, house insulation with an R-value between 30 and 60 is recommended for most areas of the United States, with higher values used in areas with colder climates. For added insulation to attics with existing insulation, R-values between 25 and 49 are recommended. Generally, it is suggested that most homeowners need to add house insulation with an R-value between 19 and 30 to their attics to realize maximum energy savings. Since new insulation installed over old insulation will cause the old insulation to be compressed and result in a slight decrease in its R-value, it is best to add an additional one-half to one inch of house insulation to compensate for this decrease.

Other Key Areas to Insulate

Another area where house insulation can be added to help conserve energy is the basement, particularly in the ceiling of unheated basements or walls of heated basements and unvented crawlspaces.

Insulated water pipes can also add to lower energy costs. It is estimated that wrapping water pipes with insulation can add two to four degrees to water temperature, so lower water temperature settings can be used.

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