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One of the biggest wastes of electricity, natural gas, coal, oil or what have you is home heating.
I was sitting here pontificating on a few things, one of them being that. The other being that, right now, I'm working with someone trying to get the temperature of his attic down. The guy's got black shingles on his roof in North Carolina, which is a very WARM climate, and his attic is hitting 175 degrees. We put a ridge vent in there, we put about four power vents, we've got gable vents...I've actually suggested putting a second roof about three feet above the first one and cutting big holes in the first one. The only reason he didn't do it was the expense.
Now let me see...we've got a roof system that's capable of heating his attic to 175°F, which means we've got a lot of waste heat we'd just LOVE to throw away. Can we turn that "waste" which we got COMPLETELY FREE OF CHARGE OR IMPACT TO THE ENVIRONMENT into usable heat? I think we can.
We'll make a shitload of small oblong black-anodized aluminum tanks...let's make them three feet long, 3.5 inches wide and 3/4" thick. Each one has a little nipple sticking out one end, and a gasketed hole in the other for a nipple to fit into. They'll have a nailing fin along one edge. The system also comes with various tubing to connect it together, a water pump, a heat exchanger and an overflow tank.
I didn't come up with those dimensions by accident. A standard asphalt-fiberglass composition roof shingle has five inches of exposure, it's three feet long and a 1x2 is 1-1/2" wide by 3/4" thick. The final piece is a Micronized Copper Quaternary-treated 1x3 starter strip--they're 2-1/2" wide x 3/4" thick--which offsets the tanks enough so that there's wood, not tanks, where you need to drive nails into the shingles.
When you install this system on the southern side of the roof--I don't see getting MUCH of a gain out of also having it on the north side--you first lay EPDM membrane on your roof deck, which should be 23/32" plywood. (Standard roof decking is 7/16" OSB.) Next, nail the starter strip to the edge of your roof and put the strips of doorskin above it on the roof deck. Then start alternating--a row of tanks, a row of 1x2, a row of tanks, a row of 1x2 all the way up until you get to the top of the roof. For short gaps at the ends of the rows of tanks, you just cut hunks of 1x4 and stick them in there.
Next, you connect the provided tubing to the end of each row of tanks. You drill a hole in your roof deck to feed the tubes into your attic, and run them to the heat exchanger and to the water pump. You add a relief valve to protect the system in case of freezing. And finally, you nail standard shingles--either standard-size three-tab shingles or architectural shingles--to the roof over the tanks and 1x2s.
The heat exchanger is just a water tank with a radiator in it; the water tank is plumbed into your hot water lines in front of a standard 80-gallon water heater. (Routing: water comes in from the mains, goes through the solar heater, into the main heater and out to the rest of your home.) The system is charged with nontoxic antifreeze. There's a device to monitor the fluid level in the system so you know if it's leaking.
Caveats: Obviously you won't get any hot water out of it at night. Just as obviously you won't get MUCH hot water out of it in the winter, especially if you live in Alaska or someplace like that. But...y'know, last I checked homes in Florida, in Alabama, in Texas, in all these really fucking hot states have water heaters. People don't install standard solar collectors for water heating, even if they can afford them, for two reasons--they're ugly, and many homeowners' associations bar them. These collectors are different: You can't see them. They're UNDER the roof surface, just working away and drawing heat away from your attic.
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