Which Shade Insulates Best: Blackout or Semi-Opaque?

R-value

• R-value is the measurement of resistance to heat loss; a higher number indicates less heat loss. Insulation in the walls of newly built homes must have an R-value of 20 to 24, depending on local regulations. Transparent materials like glass should be measured by U-value, which is the inverse of R-value, but most consumers are aware of R-value only, and window and shade manufacturers use R-value as the standard. A single layer of glass has an R-value of about 1; a triple-layered window may have an R-value of 3 or 4.

Position of the Shade

• Shades must be mounted tight to the window frame for maximum effect. A shade mounted inside the window frame requires at least an 1/8-inch gap on each side for hardware clearance. Over the length of a 40-inch shade, this gap equates to the equivalent of about a 4 1/2-inch hole in the shade. Mounting the shade to lie tightly against the outside of the window frame will help reduce heat loss.

R-value of Shades

• Large blind and shade manufacturers supply the R-value of their products; typically these numbers are available on their websites. If no R-value is available for the shade, consider the construction of the shade to determine its insulation value. A honeycomb shade, which looks like a honeycomb in cross-section, will provide more insulation than a single layer. A double or triple honeycomb shade will provide substantially more insulation. One option is to position a blackout shade inside the window frame and an additional shade outside the window frame.

Blackout vs. Semi-Opaque

• A flat single-layer blackout shade will, by nature of the fabric alone, be thicker than a single-layer semi-opaque shade, and could therefore provide a bit more insulation. If the semi-opaque shade is two layers of fabric, however, it should surpass the blackout shade in heat loss reduction. If it is honey-combed and fits tight to the window frame, it would far surpass the single flat blackout shade, while still being semi-opaque.

The Best Insulating Coverings

• A combination of window treatments, hung in the right position and made of the right layers, can have a total R-value of 15 or more. The most effective combination starts with a three-layer fabric Roman blind. It should be mounted outside the window frame and attach to the frame with magnets when in the down position. Three-layer insulated drapes hang over the blind, extending at least 14 inches past the window frame on all sides. A board-mounted valance placed at the top of the treatments completes full coverage of the window. Installing this type of window-covering system may reduce the heat loss by up to 25 percent, according to the U.S.Department of Energy.