While the sun is shining and the bugs are biting I thought I'd expound on the most energy efficient heating system in the world.
Geothermal systems can be used for both heating and cooling and work via a heat-exchange system of pipes buried in the ground (usually in your garden). It is expensive to install, but then your bills drop to like 30% of whatever you are paying now, and geothermal systems don't rely on burning fossil fuels, but utilize the temperature of the ground below our feet. You can also heat your water. So it is clean, cheap and environmentally friendly...so why isn't it compulsory in new homes?????
Anyone needing a new furnace should look into the long term benefits of geothermal systems. If I ever sell a book for a decent account, this is what I'd buy ;-)