IN ELEANOR and Michael Pinkert's house, light and heat rain down through the atrium skylight, sending showers of warmth throughout the house. In the summer, the deciduous trees softly shade the glass.

When the Pinkerts decided to build a house, they did their research first. (Pinkert is a management executive with the Psychiatric Institute of America, so he knows how you go about decisions.) First they read architectural magazines. And they thought about the sharp progressive changes that come to a young family and how you can live with them. The children are Ethan, 3 1/2, (and very proud to be wearing sneakers he tied himself the day we visited) Joshua, 7, and David, 10.

When they hired Kim Kristoff to be their architect, he sketched out the basic plan on the kitchen table, and it suited them all just fine. Each floor of the house is bigger than the next. "With cantilevering, you get free space," said Pinkert, "because you don't have to have such a large foundation." The house has a collection of sharp shed roofs with chimneys set at an angle for the look of sculpture. The exterior of the house is covered with Dryvit, a type of polymer latex stucco on nylon mesh.

"The house was planned and designed in 45 days. Yet there are few things we would do over. I think our years of planning and redesigning our dream house made it possible," Pinkert said. The house was built in nine months. It cost a bargain $35 a square foot for 4,500 square feet, in 1978.

The house is set down the hill from its turnaround of 2.3 rocky acres of poplar, oak, holly, rhododendron and beech, traversed by small streams that feed the Potomac.

You come into the house through the atrium, feeling its waves of solar heat wash over you. To the left is a private study.

The entertainment area stretches across the rear of the house. The cozy conversation area is a multi-angled room with sybaritic purple velvet sofas and a Jack Lenor Larsen chair.Persian rugs are scattered through the house, even in the kitchen. The ceiling is cedar with oak beams -- they'll never need painting. The hearth is Pennsylvania bluestone.

The dining room is, sensibly, larger than the conversation area. An informal dining area is adjacent to the large kitchen, opening through with a counter that serves as a buffet.

The kitchen is certainly the great room. A greenhouse stretches along the principal counter, both cantilevered out to bring more light and warmth to the room. An island counter has a Jenn-Air grill and cooking units.

Eleanor Pinkert is deep into cooking -- she recently finished a Szechwan course. The kitchen was designed by Dennis Manire of Shenandoah Kitchens, Bluemont, Va. The cabinets were made by Dovetail Enterprises of Berryville, Va.

The entertainment areas open onto a 70-foot rear deck roofed by the forest. The deck is built around a tree, in the best Frank Lloyd Wright form. As often happens, the bulldozer ran over the tree roots, but the tree survived.

The deck overlooks the 42-by-24-foot swimming pool. The pool patio leads to a ground floor bath, bedroom and recreation room. "Now that we have the big stove there, we fire it up every weekend," Eleanor Pinkert said. "We still have so much wood left from when we built the house, it's all free heat."

The third floor of the house has a large playroom for the children at the top of the stairs, adjoining the three children's rooms. They share a bath and the laundry room.

The parents have a spacious bedroom with a Pinkert-built bed, and comfortable chairs with a shared hassock. In the winter, the room has a view of the Maryland shore. A dressing room leads into their bath. As befits consenting adults, the bath has a wonderful extra, a deep Japanese soaking tub, plus a separate shower and a bidet.