Here are a few I mentioned in
another thread:
- Clean the furnace's/boiler's heat exchanger before heating season. The built up dust and grime reduce its efficiency.
- Put a radiant barrier behind radiator to reflect heat into the room and not the wall.
- Clean your windows before winter. In my case it let more light in than removing the screens. On the other hand, dirty windows in the summer should slightly reduce the amount of heat the enters the room.