Radiant Barriers & Fiberglass Hazards

Radiant Barriers: What Are They?

• A radiant barrier is a reflective layer of material such as aluminum installed under the roof surface of a structure to prevent the sun's radiation from penetrating the roof layer, or decking, and heating the air in your attic. A good radiant barrier acts as a reflector to send radiant energy back up and away from your attic before it can heat the air underneath. Since hot attic air is easily conducted from the attic into the living area below, a good radiant barrier is your first line of defense against the sun's heat and high utility bills.

Is Fiberglass Dangerous?

• Fiberglass insulation is designed to prevent hot air from passing into your living space from the attic above. Fiberglass is an excellent insulating material with a proven record in the construction industry. Moisture will not cause it to lose its insulating properties, as often happens with cellulose insulation. You must protect your airways and skin at all times, however, when handling fiberglass insulation, because microscopic fiberglass particles break loose during handling and become airborne.

Fiberglass Particles and Protection

• When you inhale more rapidly with hard work, these fiberglass particles tend to stick to and embed themselves in your airway. Wear a simple filter mask over your mouth and nose to prevent inhaling fiberglass particles. Wear a long-sleeved shirt to protect your skin. Even when working in heat, long sleeves are necessary because sweat attracts and holds fiberglass to your skin more than dry skin, causing itching and irritation.

Using Radiant Barriers and Fiberglass

• A radiant barrier, ideally, should contain only a layer of reflective material such as aluminum. When placed under the roof decking, it reflects heat away from your attic. Fiberglass should be installed separately either as batts or loose-fill material that is blown-in. Fiberglass, a conductive barrier, should be used on top of the attic floor to prevent the transfer of attic heat into the living area.

Good Purchase and Installation Practice

• Costly products combining a radiant barrier and fiberglass in the same material are not a good value, as these products are less expensive when sold separately. For example, a radiant barrier with a layer of fiberglass installed under the roof decking will not prevent the conduction of hot attic air through a drywall ceiling. A radiant barrier used alone under the roof decking slows heating of the attic, and fiberglass insulation on top of the ceiling prevents heat conduction into the living area through the ceiling.