If one were to be looking to purchase a new home that has strong emphasis on green building practices and high efficiency (no leaks, effective heating and cooling, etc), which builders should be considered?

Personal anecdotes about builders is also welcome. Just doing some early research.

You might want to start by talking to Kelly Parker.
As far as I know he is still involved with this company.

GWS About Page (http://www.gwssi.com/about.html)