As matter absorbs radiant energy, it is heated, develops a different temperature, and results in the conduction or convection of this heat. All substances, including building materials, wood, glass, plaster, and insulation, obey these same laws of nature. You have seen radiant barrier technology applied to the windows of houses, motor homes, and as sun shields on the windshields of autos. Aluminum foil taped to, or covering, windows or windshields are practical applications. Direction of heat transfer is a very important consideration.
Heat is radiated and conducted in all directions, but primarily convected upward.
The figures below show modes of heat gain and heat loss in homes. Following extensive research, it was determined that blocking, or creating a barrier to reduce radiant heatflow would be very beneficial in controlling summer heat gain and winter heat loss. It was also discovered that certain items in nature such as, wood, glass, and plaster absorb heat radiation, while others like gold, silver, and aluminum reflect heat radiation extremely well. A typical 90.F summer day can result in roof temperatures of 170'F, and attic temperatures of 140 F. As discussed above, conventional insulation materials, like fiberglass batts and cellulose can only delay the radiant heat from passing through to living areas of homes. Radiant barriers, by blocking this energy, have proven to be effective in keeping building structures substantially cooler in summer and warmer in winter.