How to Make Passive Solar Heat

Cut a sheet of pressure treated plywood in half across the width. Set one of the halves aside. Cut this half again lengthwise to get two pieces that are both roughly 24 by 48 inches. One of these pieces will be used as the bottom of your solar heater. Keep the scraps for future projects.

Cut your first two by six board in to two 48 inch lengths, and the other two by six board in to four 21 inch lengths. Position the 48 inch 2 by 6 boards along the outside lengths of your bottom piece and screw through the plywood into the boards. After the 2 by 6 boards have been attached along the lengths do the same for the two boards along the width at the top and the bottom of the plywood. You should now have a bottom plywood piece with a box of 2 by 6 boards surrounding the perimeter.

Set seven cans side by side on one of your leftover 21 inch 2 by 6 boards making sure to leave space between them all. Trace around each of the cans and remove them. Use a hole saw to cut out the holes for the cans and repeat the procedure on the other 2 by 6 board.

Cut out the ends of all of your soda cans and make eight tubes that are six cans in length. Attach the cans with a hot glue gun. Paint all of the tubes with a black spray paint. Use the glue to mount the tubes on the two boards and mount the boards in your box with screws. Cut a hole in the bottom at either end of the box large enough for heating ducts to fit. Mount a heating duct at either end of the box.

Cut a piece of Plexiglas to the size of the box. Apply a thin bead of caulk around the edge of the box. Set the Plexiglas in place and wait for it to dry.

Cut holes in the side of the structure that you want to heat and attach the heating ducts. As the hot air moves out of the box and into your home, cold air will move in to the box to be warmed up creating a convection cycle that will heat your space passively.