Aircrete. $2000 per structure. Fireproof, insect proof. People could build their own homes with the tools in this video. When I saw the outside, it looks like it might be a dark Hobbit House. But they are gorgeous inside. Watch at least the beginning of the video. Granted, cement has a high climate impact but there isn't a lot in these structures because it's mixed with a foam that can be made with dish soap. No kidding!