What Is Radiant Barrier?
A radiant barrier is a low-emissivity aluminum surface — most commonly foil laminated to the underside of OSB roof decking — that reflects the sun's radiant heat instead of re-radiating it down into the attic. A sunlit roof deck can exceed 150°F; an ordinary deck radiates that heat onto the insulation and ductwork below, while a foil face emits only a small fraction of it. Measured attic temperature reductions of 20°F or more are typical, which is why foil-faced decking is near-universal in new Central Texas construction, where ducts commonly run through the attic. It only works facing an air gap — foil pressed against insulation conducts and does nothing — and its benefit is cooling-season; in cold climates it is marginal. Dust accumulation slowly reduces reflectivity on retrofit-stapled foil, one reason deck-laminated product is preferred. For homeowners, re-decking during a roof replacement is the natural, lowest-cost moment to add it; as a standalone retrofit the payback is much longer.
Important Distinction
Note: A radiant barrier blocks heat radiation across the attic air space; insulation slows conduction and ventilation removes heated air — three complementary mechanisms, not competitors. It saves cooling load in hot climates and does little in cold ones.
Also Known As
These are the search terms and phrases that commonly refer to this topic, so you can find it however you describe it.
How Radiant Barrier Relates to Other Topics
A radiant barrier reflects heat and lowers attic temperature; it is not a substitute for ventilation, which removes moisture as well as heat - an attic can be cool and still wet enough to rot decking.
A radiant barrier works on radiant heat only, so it pays best in cooling climates like Central Texas and does little where the problem is keeping heat in - the same product is a good buy in Austin and a poor one in Minnesota.
Questions about Radiant Barrier?
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