Radiant Barrier in Zone 2 (Hot)
Radiant barriers do not have an R-value but reduce radiant heat gain. This page covers the effectiveness and application of radiant barriers in Climate Zone 2 (Hot).
Specifications
Radiant Barrier in Zone 2 — Guidance
Radiant barriers are most effective in Climate Zone 2 (Hot) where cooling is the primary energy concern and solar radiation is intense. In this zone, the sun heats the roof surface to extreme temperatures during summer months, and the hot roof deck radiates that heat downward into the attic space. A radiant barrier installed on the underside of the roof rafters reflects up to 97 percent of this radiant heat, keeping the attic cooler and reducing the heat load on the attic insulation below. DOE studies show that radiant barriers can reduce cooling costs by 5 to 10 percent in hot, sunny climates. For maximum effectiveness, the radiant barrier must have an air space of at least three-quarters of an inch on the reflective side. In Zone 2, a radiant barrier is an excellent complement to conventional bulk insulation — it does not replace the need for R-value insulation but enhances the overall thermal performance of the attic assembly. Installation is straightforward: staple reflective foil sheets to the underside of the roof rafters with the shiny side facing down into the attic. Avoid laying radiant barrier material directly on top of attic insulation, as dust accumulation on the horizontal surface will reduce its reflective effectiveness over time.
States in Zone 2
These states include areas within Climate Zone 2 where the Radiant Barrier requirements shown above apply. Click any state for its complete insulation recommendations.