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Does Radiant Barrier Insulation In The Attic Really Work?
Standard attic insulation below and radiant barrier insulation above.
How Does Radiant Barrier Attic Insulation Work?
Radiant barrier insulation when installed properly does work to reduce cooling costs in summer. The way that it works it that it reflects radiant heat that makes it through your roof back up toward the roof. It is best utilized on homes with metal or tile roofing and according to manufacturers such as Reflectix can reduce cooling bills by up to 20 percent. Radiant barrier insulation should be a part of a holistic approach to keeping your attic cool which also includes passive venting and active venting using solar roof vents. For more on solar attic vents see. How Solar Roof Vents Work
One reason that radiant barrier insulation is so effective is that it is highly reflective of low frequency infrared rays that penetrate the attic. The shiny surface reflects these back upwards and a foam bubble sandwich core also acts as a thermal barrier.
Radiant barrier insulation comes in pre-cut rolls from eight to thirty six inches to fit most rafters. It is easily stapled between rafters up against the underside of the roof. It can be installed in most attics in about a day. You may be eligible for a local, state or federal rebate if the work is done by a licensed contractor. For more information on federal tax rebates see: http://www.energy.gov/taxbreaks.htm
Texas A&M University Builds Two Test Houses To Study Radiant Barrier Insulation
A&M University Gives Thumbs Up To Radiant Barrier Insulation In Study
There is some controversy as to whether radiant barrier insulation reduces the life of asphalt shingles. There have been studies done by the University of Florida and Texas A & M University that show no significant heat increase in shingles on roofs using radiant barrier insulation in conjunction with full venting.
Texas A&M University actually built two homes to test the effectiveness of radiant barrier insulation. One home without radian barrier and one with. The tests concluded that there was a significant reduction in home heat gain in the test home with radian barrier insulation. There was no evidence of damage to shingles because of reflected heat.
Here are the results of a study by Texas A & M. It is PDF document. Texas A & M Radiant Barrier Study
This study should alleviate fears about using radiant barrier foil on a home that has asphalt shingles. As long as you use full venting, that is a full ridge vent and vents along the soffit it is OK.
Further studies at Texas Tech University have shown the cooling effect in a hot attic of radiant barrier insulation to be approximately 15 degrees with an asphalt shingle roof and 13 degrees Fahrenheit with a metal roof. How this translates into a certain percentage of cost reduction depends on the amount of insulation between the dwelling and the attic.
There are new underlayment products that go directly under a metal roof but for existing homes your choice will be limited to stapling the proper width of radiant barrier between your rafters up against the ceiling.
Radiant barrier insulation is among our list of green products. It appears that it does live up to most of the manufacturers claims. Here is an in-depth explanation of how radiant barrier insulation works by the U.S. Department Of Energy: DOE Radiant Barrier Information