Radiant Barrier

How does a radiant barrier differ from conventional attic insulation?

Radiant barriers perform a function that is similar to that of conventional insulation, in that they reduce the amount of heat that is transferred from the attic into the house. They differ in the way they reduce the heat flow. A radiant barrier reduces the amount of heat radiated across an air space that is adjacent to the radiant barrier. The primary function of conventional insulation is to trap still air within the insulation, and hence reduce heat transfer by air movement (convection). However the insulation fibers or particles only partially block radiation heat transfer and thus are not as effective as a radiant barrier at keeping the radiant heat from entering a building's interior through the ceiling. (SEE THE HOTBOX DEMO).

Conventional insulations are usually rated by their R-value. Since the performance of radiant barriers depends on many variables, simple R-value ratings have not been developed for them. Because manufacturers and suppliers of conventional insulation have spent millions on advertising dollars in educating the public on R-value technology, and because radiant barriers have little R-value, general reception to this technology has been slow. When more architects, engineers, and builders understand the advantage of radiant barriers over insulation, more of it will be used in building, and less energy will be used to cool or heat a building.

Emissivity is the property that determines how well a radiant barrier will perform. This property is a number between 0 and 1, with lower numbers indicating better potential for performance. The emissivity of typical radiant barriers is about 0.03 to 0.05. Hence they will have a reflectivity of 95 to 97 percent. Measured emissivity values should be part of the information provided by the manufacturer. Tarpfoil (TA/TAP-4201) has an emissivity value of .03 to .05 and is superior in its ability to block radiant heat over traditional forms of insulation while being less costly. Since it has a PE woven fabric to reinforce the foil, it is one of the strongest radiant barriers on the market

Pacific Solar Technologies (PST) stocks a high quality, low cost radiant barrier. Tarpfoil (TA/TAP-4201) is a fire retardant double sided, solid or perforated radiant barrier.

Most radiant barrier foils are baned with polyethylene bubble or reinforced by polyester yarn or fiberglass yarn running parallel or in crosswise patterns. Neither pattern provides adequate tensile or tear strength or is puncture resistant. PST's Tarpfoil (TA/TAP-4201) uses polyethylene woven cloth to enhance the tear and tensile strength and to improve its puncture resistance.

Tarpfoil (TA/TAP-4201) radiant barrier also serves as a sound barrier.

UPDATE

TARPFOIL

APPROVED

FOR USE IN HAWAII

Department of

Planning & Permitting

City & County of Honolulu

MB03-7