Low Emissivity Paint: A Good Alternative To Radiant Barriers — Especially In Retrofitted Homes

Low emissivity paint may be the only thing that stands between your attic and 140-degree temperatures caused by radiant energy. Infrared energy hitting your roof radiates into the attic. This heat energy accumulates in the enclosed attic space, causing temperatures to soar and boosting your utility bills, too.

Besides being often undersized or blocked, passive attic ventilation built into existing homes was often designed for an era of lower energy costs and does not circulate air fast enough to keep attic temperatures down. Options to reduce excessive attic heat include reflecting radiant energy with a radiant barrier installed beneath the rafters or incorporated into the roof. In existing houses, however, it may not be feasible to install a radiant barrier as a retrofit. Low emissivity paint applied to the underside of the roof can repel infiltrating radiant energy and reduce attic temperatures.

How It Works

Low emissivity formulas contain microscopic aluminum flakes. Aluminum highly reflects infrared energy. When the coating is applied to the underside of the roof, infiltrating infrared energy is repelled by the aluminum ingredients. Many formulas also include ceramic particles to bolster the paint’s resistance to heat transfer by conduction, as well as radiation. Low emissivity paints are applied to the underside of roof sheathing using conventional airless or air atomized sprayers. A typical coverage will require about 5 gallons for 2,000 square feet.

The Results

Emissivity refers to a material’s efficiency in radiating energy. On a scale of 0.1 to 1, most building materials such as plywood and plasterboard have high emissivity in the range of 0.70 to 0.95. These materials radiate heat-producing infrared energy very well. Painting wood roof sheathing with low emissivity paint can drop its emissivity rating to 0.15 or less, meaning it radiates less than 15% of the heat energy it absorbs. This can cut attic temperatures as much as 25 degrees and reduce A/C costs.

Keeping Cleveland homeowners comfortable for more than 75 years, P.K. Wadsworth Heating & Cooling is ready with creative solutions to cooling and heating issues year-round. Call us for more information about low emissivity paint.