To ensure good air quality inside, it has both an air-exchange system and a geothermal system that have filtration.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion

Also, specialty filters for the geothermal system are not available locally and have to be purchased over the Internet.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion

The former Mary Kay home was redone by the current owner: New flooring, paint, updated kitchen and geothermal system for heating and cooling.

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How about a trip to see a geothermal system at work?

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The geothermal system heats and cools using piping that goes deep within the earth, where temperatures are warmer than outside air in the winter and cooler in the summer.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion

Before you rush out and order a geothermal system, remember that furnace and air-conditioning technology has advanced as well, with new units 20% more efficient than a decade ago.

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The 12, 700-square-foot Energy Star-certified house was crafted from low-toxic materials, withstood air tightness tests on the insulation, and has a water furnace geothermal system that provides hot water, radiant floor heat and air conditioning.

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David Dwyer, the contractor who built the Yerke family's home and installed their geothermal system, says that if you have an old and drafty house you should, before putting in a fancy heating system, put in new windows, seal leaks and add insulation.

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At current electricity prices, an investment in a geothermal heat pump system can be paid off in less than eight years, says Trane, which like other energy service providers has seen a big uptick in interest for geothermal systems in recent years, from the military, schools, corporations and even residential customers.

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