James Beard, the food maven, has one. The middle school at Fort Bragg, the Beltsville agricultural station, the British Embassy and a Philadelphia restaurant called Lily's are also equipped with them.

Each has a greenhouse built by Janco, a Laurel firm that is sitting squarely on one of the growing trends in architecture--the use of greenhouses not as an area for raising plants, but for sheltering living and work areas in homes, businesses or schools.

The market for such greenhouses "seems to be expanding enormously," said David Olan Meeker, executive vice president of the American Institute of Architects.

Since the oil embargo of 1973, more and more greenhouses are being built as a way of saving energy and increasing the open feeling in buildings, Meeker said. From 1973, the year of the first embargo, to 1976, national sales increased from 480 to 972 units, and dollar volume jumped from $1 million to $2.3 million.

But for Janco, using greenhouses in homes is nothing new.

Janco was named for James A. Nearing, who formed the company in 1947. At that time, it was a home improvement company, according to Vice President Reginald Nearing, one of the founder's three sons. James L. Nearing is president and Robert Nearing is in charge of marketing.

"My brother James took some interest and his father-in-law worked at the Botanical Gardens, and we figured we would try to sell some greenhouses and build them, seeing as how we were in the aluminum door and jalousies type of business," Reginald Nearing explained.

The company took on sales representatives, first in Philadelphia, then in New England, New Jersey and New York. Now, Janco has about 77 representatives across the country, Nearing said.

Today, the firm--which Nearing said started with an initial investment of "a couple of hundred dollars"--is one of the largest manufacturers of greenhouses in the country, with sales this year expected to reach as many as 1,800 greenhouses..

This translates into sales volume of $5 million this year and $5.5 million next year, due in part to introduction of a new line, Nearing said. Added features such as insulated glass and bronzed aluminum have also increased individual unit prices, he said.

Janco has been able to keep some of its costs down because it does much of its manufacturing in-house, from making double-paned insulated glass to using its own engineering and design department to making deliveries with its own trucks.

The structures the company builds aredifferent from the greenhouses used by commercial flower growers.

"Some of your growers want a large area covered for the least amount of money. We usually don't go after that type business," Nearing explained. A key difference is that specifications for home, institutional and business greenhouses are more strict, requiring a higher quality and more expensive product.

What they do have is a complete line of home greenhouse structures ranging in width from six to 16 feet.They can be installed on decks, next to houses as lean-to structures, or as free-standing structures.

Clearly, one of the best sales features for greenhouses is their energy-saving capability. They can, in some cases, be eligible for a 40 percent tax credit for a passive-solar structure.

Because greenhouses can heat homes only partially, Nearing said the company has introduced insulated glass for residential greenhouses, which retain heat that would escape through single-paned glass panels. Insulated glass can increase the price of a greenhouse by about 33 percent. One typical model measures about 19 feet by 8 feet and has a base price of $2,383. Insulated glass adds $1,404.

But Nearing is wary of the tax aspects of greenhouses. He said his understanding of the law is that the greenhouse would have to be used only for collecting heat to qualify.

However, Meeker, and other architects, disagree. Their view is that the greenhouse qualifies for the tax credit if it is part of a passive-solar system, which means the structure must be facing south and set on a masonry or concrete base. One architect said he had heard of a concrete porch enclosed in glass which qualified for the credit.

The Janco catalog describes its products as "available with regular or factory-sealed insulated glass for passive solar use," with panels offering "heat-retentive insulation."

Nearing said he sees a growing future for the business, even if growth doesn't approach the 50 percent rate of a few years ago. In the last year, the company has invested over $350,000 in capital improvements, including two additions to the Laurel factory, new machinery and a computer system.

So far, the Northeast has been to be Janco's most productive market "because it's colder and they have shorter summers," Nearing said, although he added that business is building through the South. The Washington area, he said, has proven to be a "very lucrative" market.

Most of the expensive installations in larger jobs, such as for room additions, require contractors to set up the greenhouse. But Nearing estimated that about 60 percent of the greenhouses are installed by the customers themselves. A construction manual is sent out with an acknowledgement of an order. "It's step-by-step. The thing is, you have got to get people to read it," Nearing noted.