Does he know his stuff?
A homeowner in search of a green contractor should definitely do a bit of homework. A little knowledge can be used as a tool to quiz a prospective builder and gauge a contractor's level of expertise.
An easy way to do this is to learn a bit of terminology used in green construction. During the interview, you can toss out such terms and evaluate the contractor's ability to explain concepts such as "tankless water heater," "radiant barrier," "high-performance insulation" and "sustainable."
In addition, during the first visit to the site, an experienced contractor should quickly be able to identify areas of weakness in the home or advantageous environmental conditions. Can the contractor tell that one of the weaknesses is cold air that's coming up from the floor? At a new construction site, does he discuss orientation of the home to take advantage of or mitigate heat and cold?
The initial interview and subsequent meetings are opportunities for the contractor to promote the construction company's green science proficiencies. This is the time he should be showing that he knows more than the homeowners about what will best provide economic efficiencies, comfort and a healthy environment.