Also, the greater the temperature difference between the sides of the radiant barrier material, the greater the benefits a radiant barrier can offer. A radiant barrier reduces the radiant heat transfer from the underside of the roof to the other surfaces in the attic.Ī radiant barrier works best when it is perpendicular to the radiant energy striking it. The hot roof material then radiates its gained heat energy onto the cooler attic surfaces, including the air ducts and the attic floor. Much of this heat travels by conduction through the roofing materials to the attic side of the roof. When the sun heats a roof, it's primarily the sun's radiant energy that makes the roof hot. The radiant barrier should be installed in a manner to minimize dust accumulation on the reflective surface. Dust accumulation on the reflective surface will reduce its reflective capability. To be effective, the reflective surface must face an air space. Radiant barriers and reflective insulation systems work by reducing radiant heat gain. Most common insulation materials work by slowing conductive heat flow and - to a lesser extent - convective heat flow.
Radiant heat travels in a straight line away from any surface and heats anything solid that absorbs its energy. As the liquid or gas cools, it becomes denser and falls. Heat transfer by convection occurs when a liquid or gas - air, for example - is heated, becomes less dense, and rises. Heat flows by conduction from a hotter location within a material or assembly to a colder location, like the way a spoon placed in a hot cup of coffee conducts heat through its handle to your hand. Heat travels from a warm area to a cool area by a combination of conduction, convection, and radiation.
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