ORLANDO, Fla. - For this year's International Builders Show concept house, the New American Home offered a two-for-one deal.

There was the new house, a 5,200-square-foot, three-story "urban loft" with a price tag of $2.3 million.

And then there was the "renewed" house, a 1909 Craftsman bungalow that was acquired from the Roman Catholic Diocese of Orlando, moved next door to the new house, and doubled in size to almost 6,000 square feet.

How much of the renewed house, listed for $3.1 million plus, was original?

"About 15 percent," said Stephen Gidus, a partner in PSG Construction Inc. of Winter Park, Fla., the builder. "The house was in rough shape before we moved it, and a lot of it had termite damage, so we needed to replace and rebuild."

So does that make it a remodel or a new house?

And how did the design committee get away with building such a modern house in the Lake Eola Historic District, Orlando's original 1920s neighborhood, which has experienced a rebirth akin to that of Society Hill in the 1960s and '70s?

Those questions brought quick replies from Philadelphia native Bill Nolan, president of the Affordable Housing Institute of Orlando, who lived in Society Hill in the 1970s and has been part of the New American Home process for all of its 24 years.

"When they began rehabbing Society Hill, they were dealing with a lot of housing that needed a great deal of work to become habitable, and a lot that just could not be rescued," Nolan said. "The design of the replacement houses was 'contemporary,' drawing inspiration from the original houses and using the same materials, but not 18th-century reproductions."

Which is exactly what was done with the two Orlando houses, he said.

The fact that the New American Home was built in a city neighborhood was unusual in itself. Although National Association of Home Builders statistics still say that fewer than 5 percent of empty-nesters are moving to the "inner city" - as Gopal Ahluwalia, staff vice president for research, calls the destination - the planners of this year's home trumpeted the fact that "homeowners are forsaking the suburbs to live downtown."

Older city neighborhoods often come with lots of rules and regulations. The wishes of the Lake Eola Historic District had to be taken into account at every step, Gidus said, even when better materials than were available 100 years ago - such as termite-proof fiber-cement siding instead of wood - were proposed.

The house didn't have to match the surrounding originals, Gidus said, but the materials used and the scale of the project did.

Why two houses?

Because the size of the infill lot overlooking Lake Eola could accommodate two, said Carmen Dominguez, owner of Homes by Carmen Dominguez of Orlando, who with her daughter, Maylen, was responsible for the construction of the new home.

(The lot could accommodate a third house of a more modest size, but no one was certain when or if that would happen.)

What made the project even more unusual was the short lead time involved.

This year's Builders Show, which took place Feb. 7-10, originally was scheduled for Atlanta. But in 2005, the home builders' association decided that city was shy 75,000 square feet of exhibition space needed to accommodate the show's ever-increasing needs.

The builders' group "bought out the Atlanta contract, and we had to find another builder quickly," Nolan said. "The process typically takes five years, and we were able to do this and more in just two."

What was so special about the New American - and Renewed American - Homes?

Think "green." Just a few years ago, when the home builders' association began advocating sustainable development, few of its members were listening. Today, the organization says, a majority of them are using green building practices.

The New American Home is certified "green" under the criteria of both the group's Model Green Home Building Guidelines and the Florida Green Building Coalition. The Renewed American Home is awaiting similar designation.

The New American Home has a green roof system that includes drought-tolerant plants, artificial turf on terraces, and a cistern below the garage to collect rainwater and pump it to the terraces and roof for irrigation.

The house also is energy-efficient, and received an award during the show from the U.S. Department of Energy. It has precast concrete insulated walls, a solar voltaic system, and a high-efficiency heating/air-conditioning/ventilation system.

The 2.4-kilowatt photovoltaic system reduces the new home's energy load by an average of 9 kilowatts a day. The solar thermal hot water system preheats incoming water for tankless heaters, which are fueled by natural gas.

The basement and first and second floors are conditioned by two heat pumps. The third floor has its own gas/electric unit.

The house will use 73 percent less energy for heating and cooling and 54 percent less energy for heating water than a typical central Florida home of the same square footage.

With an eye toward minimizing hurricane damage, the house has impact-resistant, energy-efficient windows and a whole-house generator.

Both houses are examples of universal design intended to accommodate buyers who wish to live there as they get older; changing health needs can be easily met.

The two houses have the latest in appliances, materials and technology, including low-voltage systems that control whole-house lighting, entertainment and security.

Building one house is usually tough enough, but doing two houses, and in so short a time, is, one might say, a miracle.

Since members of the historic district's board had a big say in the project, what did they think of the result?

"They haven't seen it yet," Gidus said. "But they've been invited."

Contact real estate writer Alan J. Heavens at 215-854-2472 or aheavens@phillynews.com.