What they are and How they Work
A Radiant barrier is a material placed in an airspace to reduce heat transfer between a heat-radiating surface (such as a hot roof) and a cooler, heat absorbing surface such as your homes ceiling and insulation, (Yes, insulation Absorbs Heat!). A typical 90.F summer day can result in roof temperatures of 170'F, and attic temperatures of 140 F plus.
How do radiant barriers "block" heat?
On a sunny summer day, solar energy is absorbed by the roof, heating the roof sheathing and causing the underside of the sheathing and the roof framing to radiate heat downward into the attic. Radiant barriers reduce much of the heat radiated from the hot roof as it is reflected back toward the roof. This makes the attic much cooler than it would have been without a radiant barrier and thus reduces the amount of heat that moves through the insulation into the rooms below the ceiling.
Does a radiant barrier have an R-value? Not Much! The "R Value" is so small its hardly worth mentioning. " R-value's" are nothing more than a materials ability to Resist the flow of Conducted heat, NOT Radiant Heat. Insulation materials which produce R-values are designed to slow down, or retard the flow of heat from hotter air to cooler air. These materials do nothing for radiant heat which will drive in a straight line until it is either deflected, or absorbed. This means that the sun's radiant energy will eventually pass through your insulation, if it is not blocked by a radiant barrier.
The Department of Energy has a report, Effect of Radiant Barriers on Heating and Cooling Bills, which states:
"The tests to date have shown that in attics with R-19 insulation, radiant barriers can reduce summer ceiling heat gains by about 16 to 42 percent compared to an attic with the same insulation level and no radiant barrier."
Now imagine the energy you would save with reduced heat gains like that!
There are several types of radiant barriers offered. Some types include aluminum foil "Batt's", mylar sheets, and foil "house wraps" which are stapled or taped to the underside of the roof. A lot of work to install, installation leaves a lot of voids and areas not covered allow for thermal bridging or transfer of heat through wood members not protected. Hy-Tech offers a better solution,
An easy to apply, latex base paint that is formulated with pure ground metallic aluminum pigments and Hy-Tech Insulating ceramics. The combination of the aluminum and ceramics is a Hy-Tech exclusive a continuous radiant barrier film that is effective against both Radiant Heat AND heat transfer by means of conduction!