An all-solar home in the north country? It can be done

Norman Saunders invents houses - ''maximally glazed'' houses, if you will. And they are remarkable products. His ridgetop solar home in the heart of New England cold country remains within plus or minus 5 degrees of 70 degrees F. year-round without a furnace or woodstove. It maintains a constant flow of fresh air, is fully automatic, has annual operating expenses of $50, and costs slightly more than a conventional home to build - $90,000 to be exact.

That's because Mr. Saunders tinkers with his designs the way a race driver fine-tunes a turbocharged engine. So delicate is the balance of systems in Saunders's home that he will change the position of a nail to ensure the proper flow of air.

The Shrewsbury home is a major milestone in solar design because it breaks the golden rule of solar-home building; that is, you can't achieve 100 percent solar heating in a home in the northern tier of the United States while containing costs and preserving looks.

''This is a deliberate flouting of conventional wisdom and a display of what could be done,'' says Saunders. ''You can go to 100 percent solar. It works.''

That it does. On a visit to the house on a raw February day with the thermometer dipping to 23 degrees and the wind gusting, the temperature inside the split-level three-bedroom 2,450-square-foot home stood at a toasty 73 degrees. Built roughly in saltbox style, the house has a greenhouse and glass roof on the south-facing side. There is a two-car garage and a normal complement of windows.

The Shrewsbury house is the eighth in a succession of solar homes Mr. Saunders has designed, and it comes the closest to meeting his rigid goals:

* All rooms at 70 degrees all the time.

* The same temperature throughout the house with no cold bedrooms or warm south-facing rooms.

* No auxiliary heat even during cloudy, week-long, midwinter weather.

* A steady stream of fresh air (often a problem in superinsulated homes).

* Negligible cost for maintenance and operation.

Saunders has achieved virtually all of his goals by integrating most of his half-dozen or so patents in the solar field into the design. They include these trademarked techniques:

Solar staircase. A system of mirrors, parallel to the ground and mounted within the pitched south-facing roof and surrounded by multiple layers of glazing, that let the low winter sun pass through but reflect the summer sun away from the house, keeping it cool.

Heat sandwich. The use of two heat stores, one in the attic and one built into the foundation with the living space ''sandwiched'' in between. The attic heat store contains 400 six-gallon jugs lined up next to one another. They hold a total of about 18,000 pounds of water. The lower heat store consists of 100 tons of small stones laid directly on the ground.

Heat stores are used to adjust the temperature in the house and save accumulated heat for, quite literally, a rainy day. The water in the attic is generally warmer than the air in the living space. The opposite is true of the basement heat store.

The north window. Most solar houses have north-side windows that are small in both size and number. Saunders's design produces a thermal resistance of R-5, allowing large and numerous windows on the cooler north side of the house.

Dynamic insulation. The use of physics and convection to achieve a flow of air that avoids the escape of heat.

Because of the integrated nature of the house design, attempts at naming it have proved unsuccessful. William Shurcliff, who has written a number of books about solar design, including ''Saunders Shrewsbury House,'' calls it variously an attic-driven house, top-drive house, sub-and-super solar house, hydro-attic house, solar-store attic house, or solarmatic attic house. But his favorite seems to be trans-sol-attic house.

Mr. Saunders maintains that the design principles are flexible and that a home needn't retain the look of the Shrewsbury home to take advantage of the solar principles it employs. He intends to prove his theory with his next entry, a home he hopes to keep within 2 degrees, plus or minus, of 70 degrees.

Such a home would be more livable than a conventional house, he says, because there would be no need to adjust a thermostat and, because of insulation, every corner of the house would be the same temperature, unlike a traditionally heated home.