Air/Water Conditioning/Heating:

Solar Water Heaters:

https://www.youtube.com/watch?v=nC_Ql5qVs4Q From Coppertube
https://www.youtube.com/watch?v=EO8SyoGmWFw From Black Tubing

Solar Air Heaters:

https://www.youtube.com/watch?v=nuxanLdtwZQ&t=284s Old painted cans

Rocket Stove water heater:
https://www.youtube.com/watch?v=B9BQGamXLMk

Wood Gasifiers:
https://www.youtube.com/watch?v=OYbsPUNUPXs from barrel
https://www.youtube.com/watch?v=9WakGBC9gbo dangers