Energy efficiency can differ house to house
Have your home audited to see where changes can be made

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BY KEN SHEINKOPF

Published: November 22, 2008

Q: What really makes one home energy-efficient and another one not? We’ve done a few things over the years to save energy in our home. Just how much has to be done before a home can really be called efficient?

A: There really aren’t any specific levels of efficiency that need to be met before a home can be called truly energy-efficient. Rather, I think there are different degrees of efficiency in which one home can be seen as more efficient than another based on the amount of potential energy savings.

Commercial buildings have some guidelines that are more specific, but about the only way to quantify a home’s level of efficiency is to have an energy rater perform a detailed audit and give the house a rating (see www.natresnet.org for great information on home energy rating systems).

Note that you really can’t tell if a home is energy-efficient just by looking at it. While some features can be easily seen (such as roof overhangs and exterior shading devices), many are part of the basic construction and aren’t readily visible (such as the amount of insulation in the walls or a radiant barrier in the attic).

Consider a research project by the National Renewable Energy Laboratory a couple of years ago that concluded that a 2,600-square-foot home in Sacramento, Calif., could have its energy use cut by 44 percent if it had just $9,729 in improvements added to the basic home.

The major improvements proposed, along with their costs, included a solar hot water system ($2,654), upgrading the walls from 2-by-4 studs with R-13 insulation batts to 2-by-6 studs with R-19 batts along with 2-inch foam sheathing ($1,748), having an R-10 slab perimeter insulation ($1,371), air sealing improvements ($1,408), relocating ducts within the thermal envelope ($829), and assorted other measures such as using Energy Star-rated appliances and upgrading the air conditioner to a higher-rated SEER unit.

Interestingly enough, two of the measures proposed that would be possible because of the other energy-saving features would actually save money rather than costing anything extra. These are now being able to downsize the air conditioner to a 2-ton unit (saving $681) and downsizing the furnace to 50,000 Btu per hour (saving $108).

Ken Sheinkopf is a communications specialist with the American Solar Energy Society ( www.ases.org). Send your energy questions to askken@ases.org.

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