When thinking about "Building Green" something to consider is the use of solar panels. It is still a relatively young technology, you still don't see many homes or business with solar panels but it could prove to be not only an earth friendly technology but a pocket friendly technology.
If only 5% of Americans used solar energy it would be like taking the equivalent of 7,700,000 cars of the road and removing 89,600,000 pound of Carbon Dioxide from the environment (Vivint.solar).
Here is a little more food for thought;
But before you leap, do your research, ask questions, price things out.