Architect Sam Cravotta is using sun porch designs that help heat new houses being built near Winchester, Va., with solar energy.

One of his designs was adapted on a New England Log Home manufactured house built on a lot in the Apple Pie Ridge area north of Winchester. Built speculatively, the house was sold last month for $114,900.

Cravotta, 33 heads Solar Design Studio & Associates in Winchester. He said that the sun porches resemble greenhouses, with vertical glass sides and movable shades to prevent heat loss in winter and to shut out sun heat in summer.

Heat, admitted to the sun porch during the winter when the sun is low in the sky, is distributed throughout the house through ducts vented on the upper inside wall of the sun porch. Cravotta said that a concrete slab built just outside the porch reflects additional sunlight into the porch.

Additionally, the Cravotta solar houses are heavily insulated in the walls and roof. Magnetic weather stripping is used on doors. The roof on a carport is equipped with a collector device that provides heat for domestic water use in the houses.

Cravotta estimated that passive solar treatments used in the houses add less than 5 percent of the total cost.

The Solar Design Studio includes a design service headed by Leonard Fears. Construction of the houses and installation of the solar systems is handled by Heath Builders Inc., another subsidiary, headed by contractor Charles Heath. Heath also has a franchise for New England Log Homes Inc.

Model Log homes are located at an office site south of Winchester on Rte 642.

Cravotta said that three of his 18 solar houses have been built with the aid of experimental grants from the Department of Housing and Urban Development.