Build-it Bloke has had some time to work on the Little House on the Hill recently (yay!) and has upgraded our DIY solar space heater to improve its efficiency and duct it into an additional room. He used some discarded air con ducting from a local workshop to replace the collector in the roof. As well as being metal, he’s insulated between the layers to better retain the heat. He replaced two sheets of corrugated iron on the roof with laser light and painted the inside of the collector black, to maximise heat gain.
It works as it always did - air is heated in the box in the roof; a thermostat controls a fan that pushes the hot air into the rooms when it is warm and stops when it cools down. Testing of this upgrade is still underway, but it's already adding several degrees to the room temperature and that's often enough to mean additional heating isn't required during the day. The running cost is very low, representing just the relatively small draw of the circulation fan.
By the way, if you want to get the attention of your neighbours and passers-by, try working in the roof space facing the street with a few roof sheets off over the weekend – there were a lot of queries as to what Build-it Bloke was up to. He also added more ducting so we can heat the room I work in, as well as the lounge room.