Radiant Barrier

WHAT IS A RADIANT BARRIER?

Radiant barriers are materials that are installed in buildings to reduce summer heat gain and winter heat loss, and hence to reduce building heating and cooling energy usage. The potential benefit of attic radiant barriers is primarily in reducing air-conditioning cooling loads in warm or hot climates. Radiant barriers usually consist of a thin sheet or coating of a highly reflective material, usually aluminum, applied to one or both sides of a number of substrate materials. These substrates include kraft paper, plastic films, cardboard, plywood sheathing, and air infiltration barrier material. Some products are fiber reinforced to increase the durability and ease of handling.

How do radiant barriers work?

On a sunny day, solar energy is absorbed by the roof, heating the roof sheathing and causing the underside of the sheathing and the roof framing to radiate heat downward toward the attic floor. The surface temperature of the roof sheathing can easily exceed 150o F., thus heating the air in the attic to over 135oF. The ceiling absorbs this heat and re-radiates it into the building interior the single greatest source of heat gain within any room.

When a radiant barrier is placed under the rafters or on the attic floor, much of the heat radiated from the hot roof is reflected back towards the roof. This makes the surface of the ceiling under the attic cooler than it would have been without a radiant barrier and thus reduces the amount of heat that moves through the ceiling into the rooms below the ceiling.

All materials give off, or emit, energy by thermal radiation as a result of their temperature. The amount of radiant energy or radiant heat emitted is measured by its emissivity level. Tarpfoil (K-Shield) has an extremely low emissivity value--.03 to .05-- which means 95 to 97% of all radiant heat is reflected back.

Tarpfoil (K-Shield) is one of the most cost effective radiant barriers on the market and by blocking the heat, homes that use air conditioning can reduce their operating cost by as much as 33%. Click here to learn how to purchase TARPFOIL (K-Shield.)

The most effective method to cool your home is to keep the heat from building up in the first place.

TARPFOIL APPROVED FOR USE IN HAWAII

Department of Planning & Permitting

City & County of Honolulu

MB03-7