Q: What is a radiant barrier?
A: A radiant barrier is a layer of aluminum foil placed in an airspace to block radiant heat transfer between a heat radiating surface (such as a hot roof) and a heat absorbing surface (such as conventional attic insulation at the ceiling level).
Q: Who says radiant barriers are effective?
A: Florida Solar Energy Center, Tennessee Valley Authority, and University of Mississippi al conducted tests to determine the effectiveness of radiant barriers. The test results revealed ceiling heat flow reductions to be as much as 45%.
Q: Will roof temperatures increase due to the installation of a radiant barrier?
A: Yes, but only slightly. The Florida Solar Energy Center has measured the temperatures of roof shingles above attic radiant barriers on hot, sunny summer days. Peak temperatures were only 2-5 degrees higher than the temperature of shingles under the same conditions without a radiant barrier.
Q: How should radiant barriers be installed?
A: There are three methods of installation:
Figure 1: stapling the product to the underside of the top cord of the truss or roof rafter
Figure 1
Figure 2: draping the product over the rafters or trusses prior to installing the decking
Figure 2
FSK or Radiant Shield draped over the roof trusses
Figure 3: stapling to the plywood or OSB prior to installing the decking
Figure 3
Radiant barriers reduce heat gain and loss resulting in dollar savings and increased comfort in the home. Without a radiant barrier, your roof radiates solar-generated heat to the insulation below which absorbs the heat and gradually transfers it to the ceiling and the interior of the home. This heat transfer makes your air conditioner run longer and consume more electricity. A radiant barrier stops 95% of radiant heat transfer which reduces insulation temperatures and attic temperatures. A cooler attic also transfers less heat into air conditioner ducts. Radiant barriers can expand the use of space in your home such as garages, workrooms, porches, etc. New construction is the ideal time for installation but radiant barriers also can be retrofitted.
What the experts say about Radiant Barriers . . . . . . . .
A radiant barrier can greatly improve your comfort level, especially in second-floor bedrooms. During mildly hot weather, attic radiant barriers can reduce the heat enough that you may not need to operate your air conditioner at all.
James T. Dulley Author, "Cut Your Utility Bills"
A radiant barrier cuts air conditioning costs by blocking a sizable portion of the downward heat gain into the building...you can stay comfortable without air conditioning during mild weather...radiant barriers can expand the use of space in your home in garages, porches, and workrooms...attics are more usable for storage...a cooler attic transfers less heat into air conditioner ducts, so the cooling system operates more efficiently.
Ingrid Melody, Florida Solar Energy Center
Adding a radiant barrier to R-19 insulation proved more effective than upgrading to R-30. When heat gains to the cold air traveling inside A/C ducts (which are usually installed in attic spaces) were considered, all insulation/radiant barrier combinations showed faster payback periods than insulation upgrades.
Texas A & M, "Evaluation of Insulation/Radiant Barrier Systems"