OK, here's my hillbilly water heater. you need to build a three sided plywood triangle 4' high by 8' long. the front put corrugated metal recessed in about 2" no plywood behind corrugated metal. paint the metal flat black. Over the metal you attach 4'X8' lexan 1/8" is min. prefer 1/4".Leave that 2" space minus thickness on Lexan. Run copper pipe 3/4" back and forth from bottom to top up against the corrugated metal on the inside of the box. Keep the pipe within a couple inches at each pass. put box against house next to where your hot water heater is. insulate pipe to house and connect to cold and hot water supply. cold water comes in the bottom heats as it travels through the box and hot water comes out the top. you will be surprised how hot the water will be. Now during day even in winter you should have 1oo degree water supplied by the solar heater. At night it will take hours for it to cool. But make sure you have insulated the three sides of the box. Not the corrugated side. Now if your real ambitious like me you'll need a solar battery charger attach to the face of the box. inside the box put a 12 volt or two batteries. hook to charger. get a 12 volt blower and cut a hole in back and attach to your duct or directly into a room. you'll need a thermostat to turn on the blower when the temp in the box reaches 100 degrees. Get one that has a good cut off like 80 degrees. This will heat a couple rooms completely or supplement your gas or wood heat. Here is a couple important points, find the apex of the summer and winter suns and make the face angle in between that angle that way you get the best southern sun you can. This is not a material list but you can figure out what you need . If you can't I will draw up some plans and you'll be able to get them. I hope I stated this clearly, any questions let me know.