ASK THE EXPERT

Cellulose insulation and shading skylights

BY DENNIS CREECH AND ABRAHAM KRUGER

Q: We are interested in having more insulation added to the floor of our attic and have heard of a material made from recycled newspaper. Is it a good product? And can it be added over the old insulation in the attic?

A: Cellulose is an excellent insulation material and is manufactured from recycled newsprint that is treated with a fire-retardant chemical. Cellulose should be installed with a blowing machine that mixes air with the product to create the desired loft and thickness.

The contractor can blow cellulose directly over any type of insulation. The total thickness of insulation—both old and new—recommended for the Southeast is between 9 and 12 inches (R-30 to R-38).You can get a free fact sheet at www.southface.org for tips on insulating your attic.

Calculating loose-fill insulation

Suppose your attic contains 1,500 square feet of R-8 and you want to add an additional R-30. Assume the joists are spaced 24 inches on center. Since R-30 is not shown in the sample chart on page 31, use the sizing estimates for R-32 insulation. The chart shows that 63 bags are needed for 1,000 square feet; thus, for the 1,500-square-foot insulation area:

63 bags x 1,500/1,000 = 94 bags are needed for R-32 insulation.

Therefore, order 94 bags and purchase one or two rolls of R-30 batt or roll insulation to be used as blocking material. Be prepared to store the large number of bags you will be purchasing.

Q: The skylights in my kitchen make it feel like an oven. What can I do?

A: Sunlight streaming through overhead glass can be a major cause of high air-conditioning bills and uncomfortable interior spaces. The best way to shade a skylight is to secure a shade screen over the outside of the unit. Other alternatives are to glue a reflective film to the inside surface or use a light-colored interior shade to reflect sunlight back through the skylight.

If you are thinking of installing a skylight, consider a product with high-performance glazing that will reflect solar heat but not block visible light. A light tube is a special type of skylight that brings daylight into an interior room, but is smaller than a skylight so it does not cause as much of a problem with heat buildup.

Dennis Creech is the executive director and Abraham Kruger is a residential energy expert at Southface—Responsible Solutions for Environmental Living in Atlanta, www.southface.org.