After 36 years in the building business, Emil M. Keen can talk shop with the enthusiasm of a man half his years.

These days, Keen is talking about consumerism. "As I see it, my job is to get the National Association of Home Builders into the mainstream of consumer affairs," said the Northern Virginia developer-builder who was named chairman of the NAHB committee on consumer affairs - the first ever.

His agenda for next month's spring board meeting of NAHB is to set up an ethics committee in each of NAHB's 589 local associations, to schedule consumer seminars at the local level and to revise the code of ethics.

That's a big order for the man chosen by the Northern Virginia Builders Association as 1976 "man of the year." But the assignment doesn't scare him.

"The Home Owners Warranty program, which is voluntary among builder-members and non-members has been a strong step to serve consumers," Keen said. "But the emphasis on consumerism must go farther. It must encourage all builders to respond to consumer complaints, whether or not they are legitimate. There are always complaints in this business and buyers detest getting the runaround. Most problems can be resolved. If they are faced."

Before World War II, Emil Keen was graduated from Pennsylvania State University with a degree in science. During the war he served overseas with the Army Engineers. Until 1960 he built mostly in Nassau and Suffolk counties on Long Island. He was president of the New York State Home Builders Association in 1958.

He told an earlier interviewer that he ended up in Northern Virginia because he had invested in a joint venture there "that was going sour to the tune of a million dollars . . . I came down because I wanted to salvage the ship. When I got here I enjoyed it so well that I decided to stay."

During the 1960s he built the subdivisions of 'Stratford Landing, Stratford on the Potomac and Mount Vernon Manor, all in the Mount Vernon area of Fairfax County. He is currently involved in joint ventures for the development of 420 residences in Gunston Village, a condominium conversion of 59 units at Altamount in Southeast Washington. He is also a general partner in the planned unit development of Park Center on Shirley Highway at Seminary Road, a mammoth project that was slowed by the recent recession.

Keen would be the first admit that he's taking it somewhat easier these days. He plays more golf but also still regards building as a hobby because it gives him pleasure. He is a national vice prsident of NAHB, an organization he has served long. Nathaniel H. Rogg, who retired recently as NAHB executive, is a close friend.

Keen's wife, Estelle, has manged the company office for years. Now they commute between Florida, where they have a garden apartment on a golf course, and South Alexandria, where they have a condomunium apartment in a high-rise building.