Two Washington area builders are sharing in the $1.4 million awarded recently by the Department of Housing and Urban Development to more than 200 firms and individuals for designs and construction of houses using passive solar systems for heating.

Passive solar systems are those that make use of the sun's energy without special equipment. The idea is to use elements of a building's structure to collect, store and circular the sun's heat.

One local award was made to the new home building firm of Trellis & Watkins Inc., based in Columbia, for a contemporary house being built in the Muncaster Road area of Montgomery County. Another was given to architect Walter F. Roberts Jr. for a house he plans to build in Reston, where he lives and works.

The Trellis-Watkins firm, headed by Alan Trellis (former director of technical services of the National Association of Home Builders) and Wiliam A. Watkins, received a $5,000 outright grant for the design submitted for a contemporary house that has been started on a two-acre lot on Granby Road. The firm also was awarded $7,000 toward the construction of the two-story house that is expected to cost the buyer about $160,000.

Trellis said the buyer, who recently signed a contract, will get a $7,000 price break on the frame house. Trellis said that the house's windowed side will face south to gain maximum sun exposure in winter and that the roof and walls will be angled to gain sun exposure during winter and avoid it in summer.

Roberts won $5,000 for the design of the contemporary house that he plans to build in Reston and $7,000 toward the construction of the house. He said the dwelling will "actually be a brick house within a frame exterior on the north and south sides."

He said the south exterior wall will be mostly glass in a framed area. Two feet inside it will be a masonry wall for the actual house.