RADIANT HEAT TRANSFER
Of the three modes of energy transfer, radiation is the primary mode. Conduction and convection are secondary and come into play only as matter interrupts or interferes with radiant heat transfer. 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.
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.