Building the box

• Secure three 2x4's onto the flat edges of a section of plywood, to make a shallow box. The 2x4's can be screwed in on their short side, to give a 4-inch depth to the "box." Cut four sections of 2x4 that is 4 inches in length, and place them flat into the corners of the box, securing them with adhesive or screws. This will give a base to the midsection, and should be half as high as the three walls of the box.
  
  

Sandwich the air

• Cut a slightly smaller piece of plywood, and place onto the four corners. The plywood should have a 3-inch gap at both ends, between the flat corner pieces of 2x4, so that the air from the bottom can circulate once it is sealed. Paint the inside of the box (the upper air gap) flat black, or a dark color. Allow the paint to dry.
  
  

Plexiglass and mounting

• Fasten a sheet of plexiglass to the top of the three-walled box, sealed with adhesives or screws, or both. Now nearly complete, the box has a lower and upper air gap divided by a section of plywood; one end is open, and one flat side is covered with plexiglass. Secure the open end to a window, and place two smaller sections of plywood against the openings of the solar panel. The lower gap is the "intake,", and the upper gap is the "output", and the accumulated heat differential of the black painted upper gap will draw the cooler air into the lower gap. These openings can be directed anywhere that ducting will allow, but the lower intake should always be positioned lower than the upper output.