I visited with an old friend today, he has several solar collectors built and functioning, here in frigid Eastern Ontario. It was a chilly 48 degrees f here so not a bad day to see how these thing work. Here's a picture of the collector. This was his first attempt and from the inside I had noticed a hot blast of air coming from the blower. which is an antique he'd scrounged from somewhere but still very effective. The thermometer outside shows just under 150degrees f and there's no thermostat the blower just runs constantly when the manual switch is on. A closer look outside showed the intake (its a one way system overpressuring the building somewhat) While poorly placed and not using a recirculation system it provided enough heat to limit use of the oil heat in his shop area to only the very coldest days this past winter. I'd estimate that to be around 400 square feet so rather small. Not bad for a first attempt and a bunch of scrap! The collector outside uses an insulated bottom and back case lined with black steel and glazed in single pane "scrap" glass. he has two more collectors which improve on this one. I'll post more on them later.