THE BIG WASHINGTON snow last February fell just after the Raphael family moved into their new solar heated home outside Vienna. "Snow was halfway up the windows," said Audrey Raphael. "Our children skied off the hill, and we all went cross country skiing. It was wonderful."

The Raphaels could enjoy the snow because the new house -- the handiwork of all the family -- is heated by the sun. The brighter the snow, the more solar energy.

If you go up in an attic on a sunny day, you'll be hot. If the sun shines when you sit in a car, even on a cool day, you'll be warm. These two principles heat the house of architect Christopher Raphael, psychcologist Audrey Raphael and their children.

The Raphaels have one of the first -- if not the first -- Washington-area houses to use recirculated solar heated air to directly heat the house. By doing much of their own work, including the architectural design and the general contracting, they built the 4,000 square foot house for a budget (in this day and time) $140,000 (not counting land).

From the outside, you'd hardly notice this is a solar house. The walls are cedar, and the roof is wood shingles -- except for the very top where fiberglass panels act as solar collectors. But they're so far up on the steep pitched roof, they're difficult to see.

The house looks like a very pleasant contemporary farm house -- complete with dogs. It is set in the middle of five acres, and the neighbors are well-shielded by trees. The giveaway that it is not a farm comes when you look at the west forty and see a good-sized tennis court.

"We built the tennis court first," said Audrey Raphael, "and the house second. That seemed about right to me." The court proved to be lure enough to get tennis playing friends to come and help them build the court's fence, a wood and wire construction that cost them about $500, considerably under the estimate.The whole court cost $11,000.

We came into the house from the side. The entrance foyer separates the two parts of the house: adult and children. The two sections have an insulated door between, so when the children are off to college, their part can be held at a lower temperature. Rooms for the boys are on this level. Kip, the eldest son, is in school in Delaware. There's also a cosy den on this side of the house -- planned for the children but used by everybody in cold weather.

The foyer is a balcony overlooking the pleasant three-story (26 feet) high living room. The ceiling is all cedar.

"I stained the boards," said Audrey Raphael, as we went down to the living room, "But one afternoon I found that the carpenters had put up the big 20-foot long unstained boards instead. Of course, they all had to come down again. I couldn't hang at 26 feet staining boards.

The steps lead down to a bright room where the glass is concentrated toward the south. An overhang keeps the sun out in the summer.

A small greenhouse stretches across part of the living room wall. A long skinny skylight in the room brings in solar heat as well as light. A big fireplace adds cheer. The dining area is on the side closest to the kitchen, with a pass through in the wall. A planter box at the window and breakfast table level is full of hot peppers and flowers. The cabinets were custom-made by Burger Cabinets in Herndon, cheaper Raphael said, than the mass manufactured. The big red Mexican tiles on the floor help to store the sun.

Beyond the kitchen is the laundry, Audrey's study/guestroom/bath and the mudroom with a storage wall and freezer.

From the foyer, we turned and went upstairs. The daughter's room has bunk beds designed like Charles Eames' House of Cards, and a zoo of stuffed animals. The master sitting room and bedroom is at the front. The bedroom has a marvelous window above the bed to allow the moonlight to enter. A window seat is also a duct for hot air from the kitchen. A pillow on the bech has the neddlepointed message: "Avenge yourself -- live long enough to be a problem to your children."

At the ceiling level is a heat return duct. The closets are partioned off to make a dressing room on one side and a headboard on the other.

The Kohler whirlpool bathtub is built in. The walls are also lined with cedar. The bath and washbasin are in a separate compartment from the toilet and shower. Doors into the bath slide into pockets. Marble sills are set below them.

The solar hot water tank, two heat pumps, the fan and a big plywood box for rocks are all in the basement.

The Raphael's solar house isn't like most, where the sun heats water or another liquid in a collector which then goes through a heat exchanger to warm air.

"Our aim," said Raphael, "was to design a system with off the shelf parts that could be put together by a weekend carpenter." Raphael, their sons Charlie and Peter and daughter Andrea built the solar absorbers.

On the Raphael house, the high peak of the roof is covered with Fiberglas panels. Behind the rafters is ordinary corrugated aluminum siding riveted to rigid insulation. The air from the house goes through this attic collector and then is pulled by a fan down a big central duct to the basement where 110 tons of rocks fill the crawl space. The rocks are a heat sink, to store the heat during the day.

At night, the fan reverses automatically, to draw the heat out of the rocks to warm the house. The rocks also store heat collected from the top of the south-facing glass during the day. Other heat (from lights, people, cooking) is collected in a return duct at the top of the three-story high living room, and recycled.

When the passive system runs out of heat, the two heat pumps, zoned for south and north sections of the house, cut on. When the temperature drops below the ability of the heat pumps to extract warmth from the outside air, only then do the resistance heating units come on. Solar Engineering Corp. of Northern Virginia did the controls and helped with the installation. All the glass is double-glazed Pella Windows, and the house is heavily insulated.

For summer, the Raphaels could add an exterior register on the north to pull in cool night air to store in the rocks for the next day. So far, the house has been cool enough in the summer with just the central fan.

The Raphaels heat their domestic hot water with three panels of conventional water solar collectors, bought from Intertechnology Corporation. cThe water is stored in a heavily insulated tank.

The innovative passive/active solar disign was worked out by Raphael with help from Charles Michaels of New Hampshire Total Environmental Action, a consulting firm. The firm has done similiar concepts for other hybrid active/passive systems. They estimate that the solar system should pay back its $12,000 cost in 12-15 years, counting the $2,000 tax credit. Their bill for the coldest month (February) last year, when the house was still not finished and there was lots of open doors and leaky spots, was $250, including all cooking and other electricity.