THE FLOOR-STORAGE THERMAL-LOOP HOME

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By leaving openings above the east-west partitions, we were able to assure that air rising to the ceiling of the sun room will move back into the northern parts of our house. Of course, a room — like a bottle — can take in new air only if there's a way for the old to escape. Therefore, to allow the cooler, heavier air to get out, we made a vent in the floor along the entire north wall. That cooler (but still warm) air falls beneath the floor and moves back to the south, passing under our feet. A vent running the length of the south wall completes the circulation pattern.

Concrete walls (56 tons' worth in our case) provide a good deal of heat storage capability, but the thought occurred to me that perhaps we could pack away some sun-given warmth in the air path under the floor, as well. Rather than construct an elaborate rock or water storage system, though, we decided to simply use concrete blocks that could double as thermal mass and floor joists.

Nine hundred 8" blocks sit in rows spaced on 16-inch centers (which is standard joist spacing), and all the cores are lined up on the north-south axis. Air moves through the blockto-block "cave", and enters and exits from the area beneath the floor through 2-1/2-inch vents all along the south and north walls. The concrete tunnels rest on a 2" layer of pea gravel, which — in turn — sits on a sandwich of cardboard, 0.006" polyethylene, and more cardboard. We laid 2 X 4 nailers on their sides directly on the block joists and screwed a 3/4" plywood floor to the nailers.

This technique proved to be several hundred dollars less expensive than a conventional flooring system would have been, and we reduced the cost again by purchasing chipped and cracked block. Furthermore, the sanded and oiled plywood provides us with a floor that we find both comfortable and attractive.

Naturally, we could hardly wait until the construction process was far enough along to allow us to test our circulation/storage system. And once the east-west partition walls were completed, the setup's effect immediately became obvious. We find that air begins to circulate as soon as the front room warms in the sun. The flow rate is quite low at first, but as the temperature difference between the south room and the north rooms builds, the rate increases. Once a 10°F disparity has been reached, the air movement from the south wall vent can be strong enough to hold a single-ply tissue straight out and flapping like a flag!

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