If an attractive house already has a proven allure to consumers and the builder adds 59 energy-saving features, shouldn't the house be a best-seller?

The one-of-a-kind house is in a development here called Dorsey Hall, and it is probably one of the most energy-efficient houses anywhere.

But no no really knows how the house will sell if built for a mass market, and there are no current plans to build it in volume.

The situation represents one of the most perplexing riddles of the current housing situation: Home buyers need and want energy-saving features, and most builders want to supply them, but the builders are not sure what features are cost-effective, and their experience indicates buyers are not ready or able to pay for such features unless they are proven.

"We have to be very careful before we invest in or pioneer a new building technique," said Robert E. Hafer, marketing manager for the Ryland Group Inc., which built the Columbia house as part of a program sponsored by the National Association of Home Builders.

Ryland builds about 4,000 houses a year, and its production homes so far include about 25 of the energy-saving features of the Columbia house.

Other features will be incorporated into the production homes of Ryland, and probably the homes of other builders, if they prove to be economically practical.

Those features include a special fabric that was used literally to wrap the Columbia house to reduce air infiltration; a vestibule that limits the amount of cold air that can enter the house, and passive solar-energy devices that collect and store the sun's heat for release when the temperature falls.

While some of the devices and features are relatively untested in a mass-production house, none of them is considered exotic or far-fetched. Many of the products are already being used in home building, although apparently no one except Ryland has put so many of them together in one dwelling.

"Ryland has been a leader in the energy push all along," said Hafer. "But the market almost has to demand a new building technique. So far the market hasn't demanded it."

Hafer said Ryland studies have shown that energy saving is still only fourth on the priority list of most home buyers. Ahead of energy are the price of the home, the location and the overall quality.

Before building the new energy saver, Ryland had built several experimental homes with solar-energy features and tested consumer interest. The results were disappointing, said Hafer.

"In all our research studies, we found that energy (saving) is not paramount," Hafer said. "But possibly two years from now, when we're looking for every possible way to get a buyer into a home, one way will be to lower the energy bill."

In the meantime, the NAHB Research Foundation Inc. will monitor the performance of the energy-saving features in the Columbia home and determine which can pay for themselves by their performance. The monitoring equipment, supplied by NAHB, includes special recorders to keep a constant record of such data as temperature and humidity in various parts of the house.

During the monitoring period, the home will be occupied by its new owners -- a family who bought it from Ryland for $108,500. "The house was sold almost immediately," said Hafer. "We advertised it in two newspapers, and about 25 families were immediately intersted."

Hafer pointed out, however, that the price was a cut-rate one because no charge was made for many of the special energy-saving features.

"A lot of items were donated by distributors, and we didn't include them in the purchase price," Hafer said. "Those items would have added $6,000 to $10,000 to the price."

Richard Jenkins, Ryland's vice president for research and development, thinks the new home's passive solar-energy system, in which the sun's heat is gathered through south-facing basement windows rather than the rooftop collectors that typify "active" solar homes, could itself result in a 40 percent saving in heating costs.

Once the sun's heat enters the home's basement, it is stored in the basement's concrete floor, in special concrete columns that act as radiators, and in panels containing heat-absorbent salts.

The stored solar heat is released when the temperature in the house falls, and the heat circulates to the upstairs through registers in the basement ceiling.

Both Jenkins and Hafer think passive solar energy is highly promising but will be difficult to incorporate into mass-produced homes because the development's site must be oriented to give the homes a southern exposure.

"The developer will have to lay out his land so the builder can use passive solar," Hafer said. "It's something the market will want because it doesn't increase the cost dramatically and pays back (the investment) quickly."

The solar-energy system in the Colubmia house works in conjunction with a dual-compressor heat pump that doubles as an air conditioner in hot weather and will also preheat water for domestic use.

Jenkins declined to predict what energy savings might result from the home's other features, which concentrate on insulation and air-tightness. "We have so many different systems that work together in this house that it is really difficult to predict accurately what the saving will be," said Jenkins.

For example, Jenkins redesigned the wiring plan of the standard Ryland home to eliminate horizontal runs of wire that would interfere with the insulation and air-infiltration protection. Various other elements of the house, such as closets and the bathroom medicine cabinet, were relocated to get maximum insulating effect.

Hafer thinks home buyers will need to become more educated about the energy-saving capabilities and differenes in various homes before they will pay premium prices for fuel-saving features.