What States Use Radiant Barriers?

Function

• Energy from the sun causes the roof to become hot. Heat then radiates downward, heating the space below. Radiant barriers have a high reflectivity and low emittance. When fitted into roofs, they reflect the heat of the sun away from the roof. Low emittance means that they give off, or emit, little heat. In this way radiant barriers help reduce the flow of heat and will keep the roof space cooler. They are most effective when the roof space contains air-conditioning ducts. When the ducts are cool, they work more efficiently, saving energy and reducing energy bills.

States

• The Oak Ridge National Laboratory has drawn up a map of the U.S. divided into temperature zones to demonstrate the effectiveness of radiant barriers. On a scale of 1 to 8 (1 being the hottest and gaining the most benefit from radiant barriers and 8 being the coolest) the tip of Florida is categorized as a 1 along with Hawaii and Guam. The southernmost regions of Texas, Arizona and Louisiana are in zone 2, while California, the remainder of Arizona, Arkansas, New Mexico, Oklahoma and Tennessee fall into zone 3. In colder states, such as Alaska, (Zone 7 and 8) radiant barriers, although reflecting summer heat, will also reduce much-needed winter heat, making energy savings negligible.

Savings

• According the the Oak Ridge National Laboratory, homes in the deep south can gain most savings from radiant barriers. In Miami, for example, or Austin, Texas, radiant barriers can reduce bills by as much as $150 per year or even more on a special price plan. In milder climates, savings will be half that, and in northern states such as Illinois, savings will be negligible.

Considerations

• Byron Jones, director of The Institute of Environmental Research, claims that radiant barriers are not the best option for every house. He writes that the amount of energy saved by installing a radiant barrier might not justify the installation cost. Radiant barriers are most efficient when used in states with long spells of high temperatures. They should not be used instead of, but in addition to other insulating materials. Energy savings in a roof with an already high level of insulation will not be as high as in a roof with less insulation.