Department of Energy
Assistant Secretary
Energy Efficiency and Renewable Energy



  • Why Insulate Your House?
  • How Insulation Works

Which Kind of Insulation is Best?

  • What Is an R-Value?
  • Reading the Label
  • Insulation Product Types

Insulating a New House

  • Where and How Much
  • Air Sealing
  • Moisture Control and Ventilation
  • Installation Issues
    • Precautions
    • Attics
    • Walls
  • Design Options
    • Crawlspaces and Slabs
    • Advanced Wall Framing
    • Metal Framing
    • Insulating Concrete Forms
    • Massive Walls
    • Structural Insulated Panels
    • External Insulation Finish System
    • Attic Ventilation or a Cathedralized Attic

Adding Insulation to an Existing House

  • Where and How Much
  • How Much Insulation Do I Already Have?
  • Air Sealing
  • Moisture Control and Ventilation
  • Insulation Installation, the Retrofit Challenge
    • Precautions
    • Attics
    • Walls
    • Basement Walls
    • Floors and Crawlspaces

Resources and Links

About This Fact Sheet


Why Insulate Your House?

Heating and cooling account for 50 to 70% of the energy used in the average American home. Inadequate insulation and air leakage are leading causes of energy waste in most homes. Insulation:

  • saves money and our nation's limited energy resources
  • makes your house more comfortable by helping to maintain a uniform temperature throughout the house, and
  • makes walls, ceilings, and floors warmer in the winter and cooler in the summer.

The amount of energy you conserve will depend on several factors: your local climate; the size, shape, and construction of your house; the living habits of your family; the type and efficiency of the heating and cooling systems; and the fuel you use. Once the energy savings have paid for the installation cost, energy conserved is money saved - and saving energy will be even more important as utility rates go up.

This fact sheet will help you to understand how insulation works, what different types of insulation are available, and how much insulation makes sense for your climate. There are many other things you can do to conserve energy in your home as well. The Department of Energy offers many web sites to help you save energy by sealing air leaks, selecting more energy-efficient appliances, etc.

How Insulation Works

Heat flows naturally from a warmer to a cooler space. In winter, the heat moves directly from all heated living spaces to the outdoors and to adjacent unheated attics, garages, and basements - wherever there is a difference in temperature. During the summer, heat moves from outdoors to the house interior. To maintain comfort, the heat lost in winter must be replaced by your heating system and the heat gained in summer must be removed by your air conditioner. Insulating ceilings, walls, and floors decreases the heating or cooling needed by providing an effective resistance to the flow of heat.

Batts, blankets, loose fill, and low-density foams all work by limiting air movement. (These products may be more familiarly called fiberglass, cellulose, polyicynene, and expanded polystyrene.) The still air is an effective insulator because it eliminates convection and has low conduction. Some foams, such as polyisocyanurate, polyurethane, and extruded polystyrene, are filled with special gases that provide additional resistance to heat flow.

Reflective insulation works by reducing the amount of energy that travels in the form of radiation. Some forms of reflective insulation also divide a space up into small regions to reduce air movement, or convection, but not to the same extent as batts, blankets, loose-fill, and foam.

Next Section - Which Kind of Insulation is Best?

Building Envelope Research
Oak Ridge National Laboratory

For more information, contact the program manager for Building Envelope Research:

André O. Desjarlais
Oak Ridge National Laboratory
P. O. Box 2008, MS 6070
Oak Ridge, TN 37831-6070

E-mail Andre Desjarlais

This page updated on January 15, 2008.