I don't want to rain on anyone's parade with the whole pop can heater thing, but this seems like a whole lot of work, in order to collect some passive solar energy and electrically pump it into your coop. I DO believe in the collection, it is the method I question. I simply made my coop as a greenhouse. Wish I had pics. My coop is 8'X3' with the top angled at 30 degrees(4.5' in back, 3.5' in front). For the top and front of the coop, I used corrugated Polycarb from Home Depot(12'X2' sheet cost $24). You're probably thinking: doesn't the warmed air escape through the corrugations at the top? The answer is yes and no. They make/sell foam forms that fit the corrugations top & bottom, but I wanted the option of sealing the corrugated "vents" depending on heat. So, in the dead of winter I just stuff them with straw. In spring/fall I remove the straw and let it vent excessive heat . In the summer, I simply move the coop under the 75 year old apple tree, where it sees zero direct sunlight. Venting is aided by having the section of the floor beneath the roost(6'X18") be 1" hardware cloth. Since cold air doesn't rise, this hasn't been a problem, although on really windy evenings it does pose a slight problem, solved by having a wooden flap that closes over top of it. The coop door is also lower than the "living" quarters of the coop, reducing heat loss in the winter. Insulation and critical mass are the keys. Of course, the back, walls & floor are painted black where it is practical, and the feeder is and old 5gal bucket(painted black). The waterer(old 2gal bucket) is painted white. Turns out chickens don't like hot drinking water. Who does? I used pressed wood on the outside AND inside. Having used 2X3 construction, this leaves a 1.5" gap on the sides and 2.5" in the rear. The sides I insulated with straw. The back, I have filled with heavy duty, seal-able garbage bags(OK. They are animal "body bags" from the vet) filled with water. Seems to work really well. I live in Colorado where we are not only a mile high, but also have 300 sunny days a year, so passive solar is easy and reliable. In the Winter, the coop runs about 40-50 degrees above outside temp during the day, and is usually around 25 degrees warmer at dawn. In the Spring/Fall, with the vents open, it runs around 20-25 degrees warmer during the day and 15 at dawn. With the vents working in the Spring/Fall, most heating results are from the water filled wall and not the greenhouse effect. Using straw and "pet" bags as insulation really kept costs down. The entire coop was built for less than $100. It doesn't require heat pads and/or water bowl heaters. In fact, no electricity at all. Since the top is clear, I use two solar landscaping lights to help the hens in the winter. Comments? Questions?