The Greenest Building is the one never built.
This may sound counter-intuitive for an architect - don't build new buildings! But new, energy efficient green buildings only account for about 5% of our new building stock! More than 80% of our buildings are old energy hogs, so retoifitting existing building stock can make sense. It can save a lot of new resources and help reduce the waste stream that goes into building a new building.
Consider renovating! This 1920's Vancouver home has been transformed inside and out, saving resources and maintaining a heritage character in the neighborhood.