Work is underway on an 1800-lot subdivision in Louisville, Ky., that its developers say will be the largest geothermal-only community in the country.

Builders who buy lots in the North Village of Norton Commons will have a free hand on what kind of houses they build, as long as they meet general architectural guidelines, but a ground-source heat pump for heating and cooling will be a requirement.

The development is a Traditional Neighborhood Development, which includes a variety of housing types and commercial space and is designed so that people who live there can walk to many of their destinations.

Marilyn Patterson, director of marketing and general counsel for the development, said by telephone that there are a variety of advantages to requiring geothermal systems, including better heating and cooling performance, greater efficiency, and reduced environmental impact. A big part of the appeal is that no one living there will have to listen to a noisy outdoor compressor belonging to a neighbor with a conventional air-source heat pump.

In a news release, developers said that well drilling has started for heat-exchange tubing on the first 50 lots, and another 75 lots will be drilled in the spring. Construction could begin any time.

It will take 12 to 15 years to build out the entire North Village, Patterson said. The 600-acre development already includes the South Village, with about 1000 residential units, where geothermal heating and cooling was not a requirement.

Houses will range in size and cost

Houses in the South Village range in size from 1200 sq. ft. to 8000 sq. ft. and cost between $360,000 and $2 million. Patterson expects the range to be similar in the North Village but said that the first group of houses will probably be in the 2200-sq.-ft. to 2500-sq.-ft. range.

Requiring ground-source heat pumps makes the houses more expensive-from $4500 for a smaller unit to as much as $15,000 for a large house, Patterson said-but the 30% federal tax credit, good through the end of 2016, will take away some of the sting.

Builders will not be required to build to any particular efficiency level, although upgraded insulation packages and Energy Star appliances will probably be the norm. “The market demands they build efficient housing,” Patterson said.

Developers also promote the idea that people who live in Norton Commons have a lot of what they need nearby, such as local stores, schools, and playgrounds in addition to housing. As a result, driving won’t be as essential to life there as it is in many suburban settings.

“What could be greener than that?” Patterson asked.