Radiant Foil Attic Barriers

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Attic radiant barriers are designed to impede the transfer of radiant heat from the roof of a house to the attic space below. Lowering the attic temperature reduces the cooling load on your air conditioner and increases its efficiency resulting in average savings of 5% to 10% on the cost of electricity to cool your home.

The installation of an attic barrier is relatively simple making it an ideal do-it-yourself project. Basically you have two installation choices: Over the attic floor, or between the rafters supporting the roof. Of the two, over the attic floor is the easiest. Simply roll out the sheets, shiny side up, from one end of the attic to the other overlapping the sheets as you go along.

No stapling is required because you want the reflective sheets to float freely above the insulation allowing for air space underneath the barrier as well as above. If the barrier is compressed against the underlying layer of insulation it will lose its effectiveness.

One concern frequently voiced with “over the attic floor” installations is dust accumulating on the surface of the barrier and degrading its effectiveness over time. But opinions vary depending on the source. Here are two conflicting opinions from separate U.S. government agencies.

According to the National Bureau of Standards, U.S. Dept. of Commerce, “Thin layers of dust readily visible to the eye do not cause very serious lowering in the reflecting power. The appearance of the surface is not a reliable guide as to its reflectivity for radiant heat. Foil which appears dark or discolored may have lost little in insulating value if the surface film is thin.”

Now let’s hear what the Dept. of Energy has to say: “When radiant barriers are newly installed, some testing shows that the attic floor application will work better than the roof applications. As dust accumulates on the attic floor application, its effectiveness will gradually decrease. After a long enough period of time, a dusty attic floor application will lose much of its effectiveness. Predictive modeling results, based on testing, suggest that a dusty attic floor application will lose about half of its effectiveness after about one to ten years.”

I would tend to side with the Dept. of Energy, but some attics just aren’t as dusty as others depending on how they’re vented. In any case, take a minute to spend some quality time with your attic and have a look around. You may have forgotten how much stuff is up there rendering an over the floor installation ineffective as well as impractical.

If your attic is uncluttered and you decide to proceed with the over the floor installation, purchase a perforated barrier especially designed to allow moisture to pass through, and take care not to cover kitchen and bathroom vents or recessed lights.

Learn more about Attic Radiant Barriers and many other Alternative Cooling strategies at Alternative-Heating-Info.com