DonateInsulation helps buildings retain heat—around the sides of the building and the roof. But what about the floor? Even with insulation, heat extends through the floor into the earth, and that is the heat we can reuse. In the most densely populated areas, heat from below the area could be harvested annually to supply 25% of the heat used by the area’s buildings. This kind of creative approach can help us make use of the heat we generate, instead of contributing to global warming and climate change.