For example, I used extruded polystyrene under the floor of the house to insulate the heated floor from the subsoil. Polystyrene is about the only material suitable for insulating under a floor. If I had not used the insulation, quite a bit of heat would be lost to the subsoil. This would increase the need for burning more fuel, which in turn would have a greater impact on the environment over the long-run by using more nonrenewable energy and adding to air pollution. The less nonrenewable energy we use to heat and cool the house will far surpass the impact of using some unnatural materials to build the house.
Insulation comes in both natural and unnatural forms.
You can insulate a house with dried leaves, straw, feathers, wool, cotton, saw dust or just about any other organic product that does a reasonable job of preventing heat flow. You can also insulate a house using fiberglass, rock wool, and different forms of foam insulation. Fiberglass insulation is made using high-temperature gas furnaces and uses 20 to 30 percent recycled glass. Rock wool is made from the scum of molten metal and although it is a byproduct that would normally get pitched, it requires lots of energy to be produced along with the pollutants that the factories generate. Polystyrene and polyurethane are made from petroleum byproducts and other chemicals.