Green Product Sub-category: Low-Emissivity Paint

When they face a heat source, radiant barriers work by reflecting heat. When faced away from a heat source, radiant barriers function primarily by virtue of their low emissivity. This means that the surface does not radiate heat well. A radiant barrier surface on roof sheathing, for example, heats up from the sunlight striking the roof, but that heat energy is not readily emitted into the attic space—so that attic remains cooler. This is why the radiant barrier seems to "reflect" heat back out of the building. An air space is required on at least one side of a radiant barrier in order for it to function as designed. Radiant barriers in attics are most beneficial in reducing cooling loads; their effectiveness in reducing heating loads is more limited. When comparing low-emissivity aluminized paints, look for the lowest emissivity (which corresponds to the highest reflectivity), and low VOC levels. Do not rely on "effective" or "equivalent" R-values, which are only relevant in certain climates or under certain conditions.

(See also Insulating Sheathing.)

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E-Barrier Coating Sherwin-Williams Company Lo/Mit-II SOLEC-Solar Energy Corp.	E-Barrier Coating Sherwin-Williams Company
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