Eco Style

Professor Don Corner came up to Portland from Eugene on Wednesday to give a lecture on his double-skin facade research as the John Yeon Scholar. He spent last year on sabbatical touring Europe and some of the U.S. researching the topic.
For those of you who have never heard the term, a double skin facade is basically the face of a building designed with two layers of enclosure for better performance. The area in between the two facades is used to mitigate heat gain (it rises and escapes) and also to manage direct sunlight. Double skin facades are trendy right now among those architects, developers and clients interested high-performance design (design that focuses on making the building really work well, especially from an energy standpoint).
What I found interesting was that he described (quite eloquently) how they have changed from being something related to a specific purpose into something decorative and expressive, and that many of these facades are of questionable functionality. He compared them to Oregon architect John Yeon's window vents that were mimicked for stylistic purposes on the facades of buildings that were air-conditioned.
This discussion begs the question, what is a "green building?" Is this term a stylistic category or a technical one? Or, is it an essence that cannot be captured by one or the other? So many of my peers make arguments about what their building (designs) look like on the outside based upon the function of the various building parts (I have gotten into this argument several times, asking why this is important; many students and professors take the expression of function to be a given when it comes to facade design). If it is really important to express function in the form of the building, where do the two diverge? Or inversely, is there something wrong about expressing something with a facade that is not actually going on in the building, such as passive cooling or sun shading?