house

Insulate you're house against heat loss. One of the most important areas is the ceiling; installing some form of insulation such as Batts. Also think about getting windows double glazed. A less costly but important too is; draft stop insulation tape in door frames etc. Anywhere there is a small airgap and outside air can come in.

You will gain many advantages for the environment and you're own energy use; lower power heating cost and comfort.