'Sun room' heats a house

If you think solar energy is just for those who can afford a special, custom-built home, you're wrong. A visit to Frank Schiavo's 1,000-square-foot, three-bedroom house here might change your mind.

"I wanted to show how solar can work with an ordinary tract house," says Mr. Schiavo, an environmental-studies teacher at both San Jose State University and San Jose City College.

For a total cost of $3,861.66, he added a 40-foot-long, 8-foot-wide solar greenhouse -- or "sun room" -- along the back side of his home last summer. He did most of the work himself, with some help from family and friends. More than half the cost will be returned to him through federal and state tax credits.

"If a person can add a carport or patio, he can build a passive sun room," Mr. Schiavo says.

The West Coast environmental teacher said recently that he has not used his gas furnace so far this winter and that the temperature in his house has not fallen below the low 60s, despite a bunch of cloudy days when the outdoor thermometer dropped to the 30s. Also, he has not even used the fireplace.

Mr. Schiavo says that when he decided to buy a new house, he shopped for one with a south-facing back side. Further, he talked with his neighbors about planting dwarf trees so they wouldn't block the rays of the sun.

"My neighbors are gardening buffs," he smiles, "and their whole backyard is a garden. In fact, if they hadn't agreed with what I was trying to do, it would have made the project impossible."

The glass-enclosed room has a red-brick floor that warms up to 70 or 80 degrees when it is struck by the sun's rays. Then the heat radiates from the floor and back wall at a longer wavelength, so that it cannot escape through the thermal-glass walls. Simply, it is trapped in the room. A sliding-glass door and two windows can be opened to allow the warm outside air to enter, if desired.

The hot air rises and moves through the house, thus pushing the cold air into the sun room, where it is warmed up. The system is completely passive. There are no pumps, pipes, or solar collectors. In other words, there is nothing to maintain. The air circulates naturally.

Mr. Schiavo says he plans to experiment by adding 100 to 200 five-gallon rectangular cans of water against the back wall of the room to store some of the heat overnight for a secondary heat supply.

During the hot days of summer, a vent in the roof of the sun room, plus two doors to the outside, lets the warm air escape. A solid overhang shades the windows of the house when the sun is high in the summer, yet allows the low winter sun to strike the glass.

Besides heating the house, the sun room also provides a warm greenhouse atmosphere for growing food. A row of red-clay pots containing tomatoes, strawberries, assorted herbs, and houseplants lines the glass wall of the back room.Also, the soft brown carpeting in the house blends beautifully with the red-brick sun-room floor.

Summing up, Mr. Schiavo says: "Not only do I save energy but I also have a beautiful room."