Building Energy Efficiency Into a House Brings Together High-Tech, Low-Tech Options

An array of photovoltaic solar-cell roof panels for a 2,400-square-foot house costs about $25,000. (Photos By Susan Biddle -- The Washington Post)

The summer benefits of passive solar-thermal mass are greater than the winter ones. Depending on where you live in North America, a well designed passive solar-thermal mass system can provide, on average, as much as 40 to 50 percent of your air conditioning needs, Kemp said. You may still need conventional air conditioning and dehumidification, but not as much as you would with conventional construction.

In some climates zones, including half the ones in California, you won't need an air conditioner at all if your passive solar-thermal mass is properly designed, added Malibu, Calif., architect Murray Milne.

The high-tech energy options -- wind turbines and photovoltaic solar cells -- are the most expensive. They are also the most sustainable because their operation does not consume any carbon fuel or produce any greenhouse gases. Which one might work for you depends on where you want to put it.

Kemp uses a 1.5-kilowatt, 100-foot high wind turbine to provide power to his house in rural Ontario, but he said a wind turbine is not feasible in all settings. It can be noisy, it can create a "disco effect" -- the neighbors think someone is shining a strobe light in their living room -- and it must be at least 30 feet above the highest landmark in a neighborhood, which is difficult to control.

In contrast, photovoltaics, which convert solar energy into electricity, will work on any house, rural or urban, said Kemp, who also has a 1.25-kilowatt system for his house. The main drawback to photovoltaics is their cost. A 2.5 kilowatt array of solar panels on your roof -- big enough to supply about half the power needs for a typical household in a 2,400 square foot house -- runs about $25,000. This deters most buyers, but in some states, homeowners have been offered subsidies that can be as much as 50 percent of the cost.

You might suspect that a sustainable house costs more money, but the builders said that sustainable practices can save money.

A good example is disposal on a job site. For decades, most builders have filled and emptied huge garbage bins several times during the construction of a house, periodically taking the contents to a local landfill. This practice is expensive; the value of the materials that are pitched and the cost of disposal can quickly add up. It's also largely unnecessary. With a little more care, as much as 75 percent of the waste could be eliminated, several builders said.

When he started tackling it, Matt Belcher of Wildwood, Mo., found other benefits as well. Instead of clear cutting the entire building site and throwing all the debris away, as he did in the past, Belcher now clears the site by hand, cutting only those trees that will interfere with construction.

This cut his tree-related expenses in half. Belcher fells the trees toward the middle of the site so that the falling trees do not hit and damage the trees he is saving. He sells the largest felled trees to a local lumberyard and the smaller ones for firewood. What's left is ground up and stockpiled, to be used as mulch for the new landscaping. The saved trees provide not only aesthetic benefits, but also summer shade, which lowers cooling costs.

Though sustainable building practices are not widespread, many builders are adopting them as they learn about the benefits and savings, Austin builder Ray Tonjes said.

"In 10 years, we won't have green building, we'll just have building," he predicted.

Katherine Salant can be contacted via her Web site,http://www.katherinesalant.com.

© 2006, Katherine Salant

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