Do aluminum foil radiant barriers in an attic really work, and will they reduce my heating and cooling bills? – Murray
Radiant barriers work by reflecting the heat coming through your roof on sunny, summer days. Unlike fiberglass or cellulose insulation, radiant barriers do little to prevent the conduction of heat or cold through the air and have no R-value.
While not a substitute for traditional attic insulation, radiant barriers may reduce your air conditioning bill by 5% to 10% (according to the U.S. Dept. of Energy) if you live in a hot climate. Radiant barriers have little or no effect on cold air or heating bills in the winter.
There are several types of radiant barriers available, including:
- Reflective metal roofing
- Radiant roof sheathing
- Metal (aluminum) foil
Foil radiant barriers can be applied on top of rafters in new construction before the roof sheathing is installed, or on the underside of rafters on houses with an existing roof.
Don’t install a radiant foil barrier on top of attic insulation, since condensation can form under it (even on perforated foil), resulting in a buildup of moisture, which can reduce the effectiveness of insulation and cause moisture damage and rot.
- Radiant Barriers (U.S. Dept. of Energy)
- Radiant Barriers: Questions and Answers (Florida Solar Energy Center)
- Getting Adequate Attic Insulation (article)
- Insulation R-Value (article)