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Determine the right product for your attic
Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the more effective the insulation. Although a radiant barrier reduces heat loss and gain through the building envelope because it is installed in vented cavities (like attics), it is not an insulation material per se and has no inherent R-value. Reflective insulation products incorporate trapped air spaces as part of the system and will carry an R-value. Reflective insulation traps air with layers of aluminum, foam, plastic bubbles, or paper as opposed to mass insulation which uses fibers of glass, particles of foam, or ground up paper.
As an example, compare these two products:
Radiant Barrier: is two layers of foil held together by woven polypropylene. While an excellent radiant barrier for stapling over or under the rafters or on top of the attic floor insulation, it provides no resistance to heat flow and has no R-value.
Reflective Insulation: : is a double sided Foil-Foam-Foil construction with two layers of reflective foil encasing 1/4-inch closed-cell polyethylene foam (superior to bubble) to create a true insulating material impeding the flow of warm air. The aluminum is creased to create more airflow in applications, which enhances the insulation performance. The double sided foil construction is the radiant barrier.
Unaffected by moisture, it is preferable to fiberglass batt for multiple reasons. Foil-Foam-Foil insulation can be used alone or as supplemental insulation. You can use polystyrene boards, blown-in, fiberglass batt or other insulations to supplement and achieve the desired R-value.”
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