Cover the floor with carpets
Carpets are as good as fiberglass when it comes to thermal insulation and ten times better than the floor itself. They can reduce energy costs and therefore greenhouse gas emissions since they trap the heat inside. It is best if a room can be carpeted from wall to wall so that the loss is as little as possible. Not only that, but fuzzy rugs make you and your feet feel warmer which will keep you from increasing your thermostat.