Ten moderately priced, energy-saving houses are being built around the country this summer in a demonstration sponsored by the National Association of Home Builders. The builders are using energy-saving technology, "without pushing the price out of reach of the average home buyer," said NAHB President Merrill Butler.

The Ryland Group Inc. is building one energy-saving model in Columbia. It is a three-bedroom, two-story colonial house with a full basement and attached garage. Special features will include passive solar heating, supplemented by an electric heat pump. The basement floor will be tiled to collect solar heat and radiate it upward through the house.

The house will also have a vestibule at the front entrance to keep cold air out and movable thermal screens on south-facing windows to help keep the house warm at night.

When completed later this summer, the Ryland house will be sold -- with the understanding it will continue to be monitored by an electronic system to determine energy consumption.

Ryland experimented with various solar heating systems several years ago but found consumers were not interested enough. But in the meantime, many builders, including Ryland, have been incorporating such features as electric heat pumps and additional insulation in their houses to conserve energy.