"TAP" the Sun

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Now paint the exterior wall within the taped area with high-temperature, flat black paint. Spraying is easier than brushing and will give you a more effective absorber surface, but be sure to follow the instructions on the can's label.

Ducts and Dampers

You'll use sheet metal ducts to fit through the openings you've just cut out. If you're competent with metal shears and have a break for bending the sheets, you can make the ducts yourself, according to the dimensions we've provided. But if you'd prefer, just take the drawing to a sheet metal shop and have them fold up the ducts for you.

When the ducts are completed, soak them in vinegar (overnight is best) to etch the surfaces. Paint doesn't adhere well to galvanized metal surfaces, so don't overlook this important step! After the vinegar bath, rinse the ducts, dry the surfaces, and paint them. Once they're dry, fit the ducts through the openings and attach their metal tabs to the siding with rivets and to the studs or purlins with No. 8-by-1/2-inch screws. (Always wear safety glasses when riveting, since a stem will occasionally fly out with enough force to cause injury.) Caulk the seams in the ducts, the joint where they fit to the building, and all rivets and screws.

Assemble the damper frames from drywall angle (not corner bead!) to the dimensions shown (make them 1/8-inch smaller than the ducts overall), and trim 1/2-inch hardware cloth to fit over the finished frames. Attach these screen pieces to the damper frames by first drilling 1/8-inch holes about every 6 inches around each frame and then riveting (with 3/4-inch washers) the hardware cloth to the frames.

Treat the metal dampers with vinegar, rinse them, and apply paint when they're dry. Now cut pieces from a dry-cleaner bag (or other very thin plastic) to fit within the frames. Use duct tape to attach these to the top inside of each frame, and apply a thin layer of silicone caulk around the tape to prevent it from peeling away.

The finished dampers may now be "friction fitted" into the ducts, as shown in the drawing on page 34. The upper damper must be positioned so that it will open when air attempts to exit from the collector, and the lower one must be set in the opposite direction. A fine bead of silicone where the dampers meet the ducts will insure an airtight seal, but be careful to avoid getting any fresh caulk on the damper flaps. Secure the dampers to the ducts with a 1/2-inch sheet metal screw through each side.

The slightest breath of air in the desired direction should open the plastic flaps in the dampers, but any reverse action (air flowing through the collector in the opposite direction at night and thus becoming cooled) should be stopped.

Frame It

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