Last year, when the average price of a new house nationwide was $72,000 and mortgage money continued to be out of reach for many buyers, Delbert Martin began work on a house he and his wife were able to finance themselves. He expects that it will cost no more than $40,000.

The custom-designed, 2,800-square-foot house has a passive solar heating system and many special features, including a poplar bannister carved by a local artist. It is not, in other words, your typical low-budget shack.

"My original ambition was to build a house in which there was no identifiable commercial product," said Martin, a potter whose studio is nearby on the nine-acre tract. Eventually he made some compromises -- such as buying windows, because the ones he made in his kiln tended to sweat. But the house is still pretty much of an original.

He and his wife, Carol, did the design and are doing most most of the labor. He improvises as he goes along; it's an economical way to go.

"We're building the house when there's a real crunch in the economy, when people are going out of business and liquidating stock," he said. "We're able to take advantage of some really substantial savings on materials." Since he can fit his plans to the materials available, he's been buying whatever he sees on sale that appeals to him, and then working it into the design.

Some of the bargins are even less conventional. Seven years ago, Martin got his first construction experience by building his studio out of green lumber, an inexpensive method, but tricky. This time he bought four truckloads of green poplar and let it age for 2 1/2 years before beginning construction. Now he's using it for everything from exterior siding to trim around the interior doors.

He also bought some old barn beams for $500, which he trimmed and later installed as beams for the first floor. For posts, he cut three cedar trees from his property, stripped them of bark and set them into place. The 1,800-pound rock that anchors his staircase came from the side of the Potomac River cliff he lives on. He hauled it up with his tractor.

Martin, who designed his own kiln, also figured he knew as well as the next guy how to design the house's solar energy system. On the south side, he put a 16-foot-long greenhouse, an entry door, and a 16-foot trombe wall with windows at the top to let in heat. Theoretically, the warm air should rise up and into the house from the trombe wall, then come back down through cold air returns and help warm the concrete slab, which sits on block permeated with flues for air circulation.

"I don't pretend to have all the answers," Martin said, "but problems with kilns are not that much different from moving air around."

For cooling in summer, windows at the top of the house can be opened at night to let in the breeze. For winter heat, he's building a tile wood stove, and later will put in a backup furnace.

Isn't it pretty tricky, Martin is asked, trusting all that to common sense?

"We've felt that if you ask an energy consultant to come out, he has a head full of statistics and R-factors," he said, "--which are important, of course, but he tries to make your house a machine to conserve energy, and there's no consideration for aesthetics, usually. Aesthetics, for us, was important. We don't really want to rough it. But we wanted to find a balance."

Inside the house, that energy-aesthetics balance has translated into such things as two sleeping lofts, one accesible by ladder from the guest room, the other in the master bedroom; both of them are also the access areas to the cooling-system windows. Outside, there is a large screened porch off the kitchen and another off the master bedroom, both with views of the river below. The Martins plan to use the porches as primary living and sleeping centers in summer, because the house will have no conventional air-conditioning.

After a year of steady work, the Martins and their eight-year-old son are anxious to move in, probably later this summer. But Martin is already having a few regrets about the compromises he's making in the interest of saving time.

"It really grinds me to buy a commercial door," he said. "To buy a door made in a factory that you know there are 10,000 other doors just like it all over the country."

But with a one-of-a-kind house overlooking the Potomac for under $40,000, he isn't complaining to loudly.