This past week, I came upon a very interesting article about geothermal heating and cooling. It was fascinating although primarily about commercial uses. In this process, heat is taken from below the earth's surface and brought into your house in the winter. In the summer, the heat from your house is moved below, displacing cooler air (that's somewhere been trapped in between.) I don't completely follow the cooling part other than the system always has cool and warm air, and it works by bringing the appropriate temperature in with a pump - or reversing the air flow direction. This method offers many advantages:
1) It's energy efficient.
2) It's renewable.
3) It's green - no carbon emissions as well as no carbon monoxide in your house.
4) Operating costs are cheaper than traditional forced air or radiant systems.
5) It can also be used to heat your water as well as a pool, if you have one.
This is still fairly rare. And installation is more expensive, requiring laying a grid several feet deep in your yard or drilling "wells" up to several hundred feet deep on your property. I saw comments that it was 50% more expensive, but frankly, I think that assumes to the actual unit - not the drilling.
So I think this could be very expensive to install initially. However, it's an incredible smart idea and one that offers tremendous benefits long-term. So keep your eye on this. As demand grows, prices will come down, even for the drilling, most likely. If you're building a new home, it may be something to look into. If you are especially environmentally conscious, you'll definitely want to explore this. If you need to replace your furnace, I'd wait before I went this direction.
If you have installed a geothermal heating/cooling system, tell us about. Just leave your story in the comments.