Plastic Bottle Insulation

While student teaching this winter, I took on the project of building our 1st grade class a greenhouse made out of 2 litre plastic bottles. I had originally come across similar projects being done by classrooms in the U.K. and thought this would be a great way to teach the kids a number of valuable lessons involving energy, sustainability, recycling....not to mention growing plants. While gathering the 1700 bottles needed for this project, the thought occurred to me that some combination of bottles and sheet plastic would probably make an excellent insulation for under the floor of the sauna house. Years ago I spent a summer outside of Telluride, Colorado working on a Mike Reynolds earthship house and I remember using a combination of aluminum cans and mortar to make up the walls joining the top of the rammed earth tire walls with the ceiling. Trapped air, after all, is one of the most effective (and cheapest)insulation barriers. I've since discovered scientific support for using plastic bottle insulation from a study coming out of the mountains of Nepal. The study was commissioned in response to the problem villages in this region were having with being overwhelmed by huge amounts of non-degradable plastic brought in by Trekkers. The study examined the insulation value of a full range of plastic products and determined that in fact plastic bottles and other products offer excellent insulation properties and would be an excellent insulation for the walls and floors of the villagers' homes and barns. So with the building of my Sauna floor coming up next week, off to the dump I go.