All About Insulation

Image Gallery COURTESY U.S. GREENFIBER

by Dan Chiras

Make your home more comfortable and energy-efficient with today's insulation options.

Insulation serves one primary function: It retards heat flow into and out of homes. During sultry summers, insulation helps a building keep its cool. In the depth of bone-chilling winters, it helps hold the heat inside our homes.

Choosing the correct amount and kind of insulation, and properly installing it in the walls, ceilings, floors and foundations of new and existing homes will make your home more energy efficient and economical, and much more comfortable. And, if extra insulation is paired with airtight home design and cost-effective, passive-solar heating and cooling measures, you can greatly reduce, even eliminate, the need for additional heating or cooling, and free yourself from utility-supplied power.

INSULATION INFORMATION

Insulation falls into four categories: (1) loose-fill, (2) blankets (rolls and bats), (3) rigid foam and (4) liquid foam. Loose-fill and blankets are typically used in attics, between roof rafters, in wall cavities of wood-frame homes and between floor joists. Rigid foam insulation usually is applied externally. Liquid foam is most often used in wall cavities or to seal air gaps in a home's envelope.

When selecting insulation to use in your home, consider the following factors: long-term performance; insulations' raw materials, including recycled content; environmental impacts from its production; and health impacts to installers and your family.

DOES YOUR INSULATION MEASURE UP?

When you're ready to retrofit your home for insulation, first find out how much insulation is already in place. To measure attic insulation, measure the insulation's thickness, then determine the R-value (from the table below) by multiplying the measured thickness by the R-value for the type of insulation you have.
Once you've determined the R-value of the existing insulation, you'll need to figure out how much more you'll need. Find your zone and the recommended R-values on the table on Page 65. Subtract the R-value of your current insulation from the recommended R-value to figure out how much insulation you need to add. For example, if your cellulose attic insulation measures 10 inches thick, you have an R-value of about 35. If you live in Zone 2 and heat with gas, the U.S. Department of Energy recommends an R-value of 49 in your attic.

Next, determine if you have the space available to add the insulation you need. This is done by taking the R-value you would like to achieve and dividing it by the R-value per inch of the insulation material you'd like to use. This gives you the approximate thickness needed. In this example, to achieve an R-value of 49, you'll need an additional R-14 in insulation, or 4 inches of loose-fill cellulose insulation (14 divided by 3.5 equals 4). Most serious energy-efficient builders strive to achieve levels higher than these minimum recommendations.