Sustainable design makes a lot of sense to me. That's like green buildings utilizing solar and geothermal heat pumps and such, as opposed to petroleum based energy, correct? There is a fun video on youtube:

http://www.youtube.com/watch?v=Z5rxV3R9RbQ
She wrote to yahoo groups wastewatts:
- I created this six-minute
video on You Tube to show the installation of my geothermal
waterfurnace. In terms of emissions, it's the equivalent of taking
two cars off the road forever. It might be a realistic alternative
for those of you who have some land. It pays for itself and it is
reliable. Thanks for looking -

Bonnie Bucqueroux
It's pretty neat, Ive seen this done using the stable temperature from a pond.
Brian