Radiant barriers are installed in homes—most commonly in attics—to reduce summer heat gain and winter heat loss, which helps lower heating and cooling costs. The barriers consist of a highly reflective material that reflects radiant heat rather than absorbing it
Until now the only types of radiant barriers available were foil film, metalized plastic film, and metalized "chips" . These types of barriers are installed by attaching to the underside of the roof with staples or sprinkled about on top of the fiberglass insulation on the attic floor. Premier Insulation's HEATBLOC ULTRA is the highest rated radiant barrier spray.
When the sun heats a roof, it's primarily the sun's radiant energy that makes the roof hot. A large portion of this heat travels by conduction through the roofing materials to the attic side of the roof. The hot roof material then radiates its gained heat energy into the cooler attic (some of the roof's heat will radiate in other directions too). A radiant barrier reduces the radiant heat transfer from the roof to the attic space.
A radiant barrier's performance is determined by three factors:
Emissivity (or emittance) – the ratio of the radiant energy (heat) leaving (being emitted by) a surface to that of a black body at the same temperature and with the same area. It's expressed as a number a between 0 and 1. The higher the number, the greater the emitted radiation. HEATBLOC ULTRA has a emissivity of .19, thereby blocking 81% of the sun's heat.
Reflectivity (or reflectance) – a measure of how much radiant heat is reflected by a material. It's also expressed as a number between 0 and 1 (sometimes, it is given as a percentage between 0 and 100%). The higher the number, the greater the reflectivity.
The angle the heat wave strikes the surface—a right angle (perpendicular) usually works best.
Radiant barriers are more effective in hot climates than in cool climates. Some studies show that radiant barriers can lower cooling costs10-15% when used in a warm, sunny climate. The reduced heat gain may even allow for a smaller air conditioning system.
