Build a cheap solar heater for $350
Construction Tips
It took me about three, eight-hour days to build and install the collector. Follow these suggestions and you may be able to do it in less time! First, measure your building’s south wall to determine what changes you will have to make to the collector design. Pay particular attention to the vertical height available and to stud spacing. Next, lay out the vent locations. They should be offset enough from the wall studs to allow the verticals to be lag-bolted from inside the building. Mark the vent locations on the inside and outside of the building to ensure no conflicts exist. After you are certain the layout is correct, take a deep breath, and cut all of the vents. For the frame, cut the top sill long enough to lap over the end verticals by at least 1 inch (2.5 cm). Bevel the back of the top sill so that it slopes about 10 degrees when fitted against the siding. Next, cut all the verticals, noting that the two end verticals are longer because they extend below the lower sill. The tops of the verticals must be cut to match the slope of the top sill. Gang the verticals together and cut the notches for the two, 1- by 1-inch horizontal glazing supports. Prime and paint everything. Although you do not need to repaint the siding under the collector, painting it a dark color will improve the collector’s efficiency slightly. Keep in mind that a muted version of this color will show through the collector screen, so be sure it meets your aesthetic sensibilities.
Click the picture below, to make it larger...
Each of the ten top vents and ten bottom vents measures 4 by 18 inches (10 x 46 cm). These are simply holes cut into the building. Inside the building, ten flapper valves made from light plastic sheeting prevent backflow through the upper vents at night. Half-inch (1.3 cm) hardware cloth is installed under the plastic sheets to prevent the flappers from being sucked into the vent at night. In the summer, blocking off the top vent openings helps prevent the building’s interior from overheating. I just staple a piece of cardboard over each top vent, but you could install hinged vent doors. Shading or covering the panels during the summer might also be effective. In the spring and fall, you can close some vents and leave others open to control the temperature inside.
After the paint has cured, mount all of the verticals to the siding. Take care to keep everything level, plumb, and straight—this will save you a lot of four-letter words later. I fastened the verticals to the wall sheathing and siding from the inside using lag bolts. If your siding is not strong enough for this, consider mounting the verticals from the outside, using lag screws through the verticals and into the wall studs. Next, attach the top and bottom sills. Use flashing above the top sill if desired. Then, seal the collector frame with silicone caulk. Mount the battens that will support the screen absorber. Staple the window screen onto the battens. You can fold the edges of the screen to make it fit in the slightly less than 48-inch (122 cm) bay widths. Make five 4- by 8-foot (1.2 x 2.4 m) glazing panels by joining pairs of the 26-inch-wide by 8-foot-long corrugated panels. Overlap the panels by one corrugation, and apply a light bead of silicone between the overlapped sheets. Fasten the overlapped corrugations to a 1- by 1-inch wood strip using screws with EPDM washers.
Install the horizontal 1- by 1-inch glazing support strips to the collector frame. The surface of the strips should sit flush with the surface of the collector’s frame when installed in the notches of the 2 by 6s. Do any cleanup, caulking, or other work you need to do inside the collector frame now! You won’t be able to get to the inside after the glazing is applied. Next, mount the glazing panels. Install the “wiggle” closure strips, which fill in the contours of the corrugations, on the top and bottom sills. Run caulk beads on the first set of verticals and mount the first glazing panel section. (You’ll quickly find out how square your frame is.) Fasten the panel sections to the frame using screws with EPDM washers. Install the rest of the sections in the same way. Overlap each new section over the last section by one corrugation, using a bead of caulk in the overlap. Make the flapper valves for the ten inside top vents. I used two thicknesses of plastic garbage bag for each flapper. Before attaching the flapper, attach 1/2-inch hardware cloth over each vent. Then, staple the flappers along the top edge of the vent, just above the vent opening.
