THE HELIO THERMICS SOLAR-HEATED AND -COOLED HOUSE

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THE BACKUP HEATING SYSTEM

The Grangers are quick to admit that—just like most solar-heated structures—their Helio Thermic house can be temporarily "put out of business" by three or more solid mid-winter days of heavy cloud cover. Unlike a great number of other sun-warmed buildings, though, theirs is so well insulated that it can be supplementally heated with nothing but an ordinary 50-gallon, quick recovery, gas-fired domestic water heater!

The hot (140° F) water is pumped through a heat exchanger (something like an automobile radiator) within the Helio Thermic air handler. There, some of its thermal energy is transferred to the air passing around the heat exchanger's coils and the warmed air is then distributed throughout the house.

Interestingly enough, the water which returns from the exchanger is still hot enough (130°) to pipe right into the dwelling's plumbing for washing, bathing, and other household uses. And—at current natural gas prices in the Greenville area—a whole week (which would be, to say the least, highly unusual) of heating the entire Helio Thermic prototype with this backup source of warmth has been calculated to cost only $6.80.

And if that irregular and highly unusual expense bothers you, you should realize that the Granger boys are more than getting it back on a regular basis directly from their building's attic/collector. What they've done, you see, is paint some copper tubing black, lay it out on the attic's floor and then connect one end of the bed of piping to the bottom and the other end to the top of an electric water heater's tank (the unit's heating element has been removed). This very simple solar-powered heater can warm its water to a torrid 170° F and it supplies the Helio Thermic prototype with a large part of all the hot water its residents need.

THE BACKUP COOLING SYSTEM

Even though it was never actually necessary to supplementally cool the Helio Thermic house during its first summer, the Grangers did do a limited amount of experiments with the idea just to see how it would work.

"You can bolt a big air conditioner right into the building's ducting and use it to 'overpower' any uncomfortable heat in the house on a really hot day if you want to," says Mike. "We think it's a lot smarter and less costly, though, to u se a much smaller conditioner and just run it on the few nights when the outside air temperature doesn't drop enough to cool the rocks in the structure's storage bin. On such nights, the small conditioner can be used to cool the storage pit . . . and then the bin of rocks used to cool the house during the following day."

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