Solar heating panel? A bunch of wooden/plywood boxes, some glazing for them (can actually reuse thrown-away window panels), a bit of plumbing with PP pipe (ridi

Solar heating panel? A bunch of wooden/plywood boxes, some glazing for them (can actually reuse thrown-away window panels), a bit of plumbing with PP pipe (ridiculously lego-like easy), some kind of top tank (a common steel drum?). And some making sure the roof/attic floor doesn't collapse, which usually is not a problem. This can be _build_from_scratch_ in a couple of weekends with a best friend. But for the construction codes. And unions. It's so low-tech, so I wonder why I haven't heard of 19th century installations. Me, I actuially built two in places where construction codes are not an issue. And have seen functioning installs dating from 1950s. I don't think it even makes any sense to mass-produce heat boxes the way the solar-electric panels have to be. It all can be either made on site or included into the house design from start. That's maybe why you can't buy solar heating off the shelf.