Passive solar heating features are being used increasingly in new contemproary homes, but Montgomery County builder Jay Wohlfarth recently decided to take advantage of winter sun rays in a traditional English colonial dwelling in his Quail Run subdivision.

Essentially, the $290,000 south-facing house conforms architectually with the other 42 houses that Wolhfarth's firm has built in the small subdivision. The difference: This brick dwelling has a two-story solarium room in front, with four wide, floor-to-roof arched windows to capture sun rays in winter. Even the front door is set into a similar frame to provide extra light and sun.

Wohlfarth, a Quail Run resident who has been building there since 1969, said he designed this house to have a heat-collecting solarium room with a brick floor and interior wall to capture free heat and circulate it by gravity through the rest of the house through a large-volume, low-velocity heating system.

In summer the solarium is cooled by natural ventilation supplemented by a vari-speed, 36-inch attic fan.

With a total 4,300 square feet of living space and a three-car garage, the house at 15396 Quail Run Dr., just east of Darnestown, is sited on a one-acre lot with evergreen trees on an upward slope to protect the dwelling from winter winds. Windows are double-paned. The walls have R-13 insulation and the ceiling R-30. Wohlfarth put few windows on the east and west walls that are shaded by deciduous trees.

Does the unobtrusive passive solar system work?

Wohlfarth said that the house was comfortable for his interior carpentry and finishing crew last winter. He said a minimum of gas-fired circulating heat was used. The gas bills for January and February totaled only $102.99, while maintaining a temperature of 65 degrees inside. Wohlfarth credited the simple solar system for the economy of operation.

Susan Wohlfarth, who works closely with her husband in helping to build and sell his houses, said that the solarium room stretches across the entire 50-foot width of the house and has a depth of 12 feet and a 17-foot ceiling. She said the room would be ideal for hanging plant baskets, small trees and plants because it basically is a California sun room.

In addition to the fronting solarium, the first floor has large main living area plus a kitchen and master bedroom, all of which open into the solarium through french doors. There are three bedrooms and two baths on the second floor that has french doors and two balconies overlooking the sun room.

John Spears of Potomac Energy Group did the solar engineering for Wohlfarth, who designs his own houses that now range over $200,000. The builder said he did not install a costly active solar system that stores and circulates heat because he is not satisfied that it would not be cost-effective.

"In this instance, there was no extra cost, other than allocating the space for the solarium, which can be used as a reading room or for dining and entertaining," he added.

Quail Run is located just off Route 28, several miles west of Gaithersburg and slightly farther northwest of Rockville. The entrance is on Jones Lane. The new house, which is the only one Wohlfarth has for sale, is open Saturday and Sunday afternoons. Wohlfarth has been building homes since 1953.