What is a radiant barrier?
A reflective insulation reduces radiant heat transfer across air spaces, by using one or two layers of high-reflective / low-emittance surfaces. Reflectivity must be greater than 90%, and emissivity must be lower than 10%. This rate of heat transfer can be quantified in an R-value (for a specific application). Reflective insulation is composed of one or two layers of pure aluminum, which reflects 97% of radiant heat, surrounded by an inner core of bubble or thin fiberglass. Reflective Insulation is considerably more effective than conventional insulation in reducing radiant heat transfer. The inner core contains an air-retention layer, which acts as a thermal break, effectively reduces conduction, and provides increased tear and puncture resistance. Radiant Barriers are also composed of one or two layers of pure aluminum, but do not include an inner core or thermal mass. They are scrim-reinforced for tear and tensile strength. Radiant Barriers are often perforated for breathability, an
Radiant barrier is a material that is a poor re-transmitter of infrared waves (radiant energy). By definition, this re-transmission characteristic (emissivity) must be at or below 10%. The emissivity of Reflectix products is approximately 4%. Therefore, when a radiant barrier is installed in a residential attic, it blocks 96% of the radiant energy that is being radiated by the hot roofing materials. This equates to a cooler attic, resulting in a house that requires less air conditioning usage to maintain comfortable inside temperatures.
A radiant barrier is an energy saving product installed in the attics of homes and buildings, it is excellent at reflecting heat and poor at absorbing heat. A good example of a radiant barrier is aluminum foil that is placed on top of a casserole to keep the top from burning. It works by reflecting the heat back into the oven. A properly installed radiant barrier does the same thing in your home, reflecting the sun’s heat back out of the home, reducing the heat load on your home.
A radiant barrier is a product that features a low emittance surface(s) (normally aluminum foil) that is designed to significantly reduce heat transfer between a very hot and high radiating surface (bottom of a roof deck) and a cooler highly absorbent surface (like insulation on top of a ceiling). The lower the emittance (radiation rate), the better the performance.
Heat penetrates buildings in three ways: conduction, convection and radiation. Radiation is the transfer of heat by electromagnetic waves known as thermal radiation. Thermal radiation is a form of invisible light that travels through the air from a warm to a cool surface. Warm surfaces, such as roof decks warmed by the sun, will radiate or emit their heat to cooler interior building surfaces. Radiant barriers address heat flows by radiation. A radiant barrier is a low-e surface placed in the path of thermal radiation that blocks heat transfer.
