The greenest building is the one already standing, even if it is a former gas station. In St. Louis, preservationists are celebrating the adaptive reuse of a landmark gas station known as the flying saucer into a Starbucks. According to Michael Allen in Next American City,
The gas station, which later became a Del Taco restaurant, essentially consists of four tapered columns supporting a hyperbolic paraboloid, or tapered round roof — hence the nickname “flying saucer.” Richard Henmi served as project architect on the saucer for the firm Schwarz & Van Hoefen, and the gas station was completed in 1967. Now retired, Henmi was able to fight for its preservation and see its adaptive reuse.
I am not certain that Michael has his geometry right; hyperbolic paraboloids, shaped like Pringle chips, were very popular mid-century modern structures that were very strong and efficient in their use of concrete and reinforcing. Most, like this famous house in North Carolina, are gone. This one was going to be demolished for a big box drugstore, but was saved because of the grassroots campaign to save a fun bit of mid-century modern architecture, perhaps our most threatened genre.
I complain often about Starbucks and their so-called "green" suburban drive-throughs, but I cannot complain about their urban interventions, where they are a force for good in architectural preservation, being one of the few uses that can comfortably slip into almost every old building. Congratulations to them, and to the successful St Louis Save Our Saucer campaign.