Energy use in the home generates over 20 percent of domestic greenhouse gases. Between 50 and 70 percent of the energy used in an average American home is consumed by heating and cooling systems.[1] Although there are numerous factors to consider when seeking to maximize a home's energy efficiency (see the DOE's whole-house approach), the US Department of Energy (DOE) lists inadequate insulation as a leading cause of home energy waste because it forces even the most efficient heating and cooling systems to work harder and consume more energy.

Heat naturally passes from warmer objects and areas into colder ones; insulation provides a barrier to slow down this transfer.[2] Less heat transfer means more energy saved and lower pollution levels: the Rocky Mountain Institute estimates that upgrading insulation in the attic, walls, and basement of the typical American home will reduce that home's CO2 emissions by 4,147 lbs per year.[3]

Potential energy savings

The energy savings available to consumers seeking insulation upgrades vary widely: current home insulation status, geographic region, and budget constraints all factor into the level of efficiency insulation can provide. One study conducted by the Minnesota Department of Commerce found that adding varying degrees of insulation and sealants helped reduce energy costs in pre-WWII homes by anywhere from 35-65 percent, depending on the level of investment undertaken. However, such investments usually required nearly 10 years to pay for themselves in terms of energy bill savings alone,[4] and many homeowners cite uncertainty about long-term residency as a deterrent to upgrading their insulation.

Types of insulation

A wide variety of insulating materials are available to consumers. The type of insulation best suited to each home depends on the local climate, space limitations, budget concerns, and the preferred installation method. The DOE breaks insulation into the following categories:[5]

  • Blankets: batts or rolls of fiberglass or rockwool. Cotton fiber batts are also available in some areas.[6] Blankets work well for do-it-yourself projects when space is relatively free from interior obstructions.
  • Loose-fill or Spray-applied: Usually blown in or sprayed-in-place with professional equipment, available substances include rockwool, loose fiberglass, cellulose, or polyurethane foam.
  • Rigid insulation: Any among several types of condensed foam board; best suited for maximizing R-value with minimal thickness.
  • Reflective barriers: Foil-faced materials designed to be particularly effective in preventing heat transfer via radiation.

Cellulose and fiberglass are thought to occupy between 80 and 90 percent of the US insulation market.[7] Other emerging alternative insulation solutions include wool, hemp, straw bales,[8] and NASA-developed aerogel. [9]

Installation costs and concerns

The cost of installing insulation is highly dependent upon the materials selected and the type of installation planned. Increasing insulation levels beyond the minimum requirements for state and local building codes—and in turn maximizing a home's monthly energy savings potential—is generally considered easiest and most cost-effective when building a new home.[10] Within older homes, insulating the attic is usually the easiest way to reduce energy consumption without significant construction and expenditure, although upgrading insulation throughout the whole building envelope will still provide the maximum levels of energy efficiency.

While properly installed insulation offers significant savings in heating and cooling efficiency for the average homeowner, improper installation can limit energy savings by as much as 25 percent.[11] Gaps created by uneven compression or distribution of insulating materials permit air flow and increase a home's vulnerability to moisture damage. Failing to seal against air leakage (often referred to as infiltration) prior to insulating will likewise limit the potential benefits of any improvements, as most types of insulation protect only against the flow of heat, and do not impede that of air; however, densely-packed cellulose—along with select varieties of solid foam—have proven effective in preventing the flow of both heat and air within a building's envelope. Furthermore, insulation can be applied to numerous complementary areas within a building's heating and cooling system, including air ducts, pipes, and water heaters.

Government regulation

The US Federal Trade Commission (FTC) requires full disclosure of insulation levels and materials during the sale of any new home, and many state or local building codes specify minimum insulation requirements for new homes and building additions.[12] The DOE cautions that 80 percent of homes built before 1980 suffer from inadequate insulation.[13]

Tax breaks and incentives

In the US, upgrading your home's insulation may qualify you for tax incentives at the federal, state, and local levels. For detailed information, see these resources:

Related health issues

  1. Several types of insulation may contain VOCs (volatile organic compounds), chemicals which become a gas at room temperature and may be released into the air through a process commonly called off-gassing. Formaldehyde, classified by the US Environmental Protection Agency (EPA) as a probable human carcinogen, is one such VOC used in several types of insulation as a bonding agent or solvent. While urea-formaldehyde foam insulation (UFFI) was once common in home construction, it is seldom installed today after being banned by the US Consumer Product Safety Commission (CPSC).[14][15] Older homes containing UFFI are not likely to pose a health risk due to the substance's diminishing emissions of VOCs over time.[16]
  2. Formaldehyde can still be found in varieties of fiberglass and rockwool insulation, and may also offgas from the newsprint ink residue found in cellulose insulation.[17] Although the CPSC does not note any specific warnings about the formaldehyde content in today's fiberglass insulation (and makes no mention whatsoever of formaldehyde content in rockwool or cellulose), 10-20 percent of the population may have hyperreactive airways making them susceptible to formaldehyde-induced irritation in their eyes and respiratory tracts at minimal concentration levels.[14] Fiberglass fibers may cause similar irritation symptoms when touched or inhaled, but - despite years of controversy - the American Lung Association does not currently classify the material itself as a cancer risk.[18]
  3. Asbestos, a known carcinogen, was also once a common additive in insulation, particularly vermiculite insulation.[19] Homeowners who suspect their residence is insulated with vermiculite should avoid any contact with their insulation, as even casual handling may result in dangerous levels of airborne asbestos exposure.[20]
  4. Moisture often accumulates within the insulation of buildings lacking adequate ventilation systems; this can decrease the insulation's effective R-value while increasing the likelihood of mold growth, particularly in cellulose insulation. Fiberglass, cotton, and certain foam materials may also be vulnerable to moisture accumulation and mold growth within a building's envelope.[21] Molds produce allergens and irritants, as well as toxic substances called mycotoxins, all of which may contribute to hay-fever symptoms, rashes, and asthma attacks in individuals who breathe mold-contaminated interior air.[22] Moisture buildup may also occur when wet-blown insulation is not allowed to dry sufficiently during installation.[23]


  • building envelope: The collective components which act as a buffer between a building's interior and the outdoor climate. Consisting of a building's roof, exterior walls, windows, and doors, the envelope regulates the indoor environment by controlling how energy flows between the interior and exterior.[24]
  • R-Value: measures the Resistance to heat movement provided by a given material or substance - usually a window or wall assembly. Recommended R-values for insulation vary widely based on regional climate factors and state or local guidelines. Installing insulation that exceeds the recommended R-value for your region usually provides the most significant energy savings potential. Note that R-values of certain materials can decrease over time due to settling and moisture damage.
  • infiltration: uncontrolled air leakage through a building's envelope.

External links