Private Letter Ruling 201043023
This was orignally published on PAOO on 11/6/10.
I'm going to do this as bonus post, because I don't have the ability to expand on it much. They have figured out a way to make a "curtain wall" of glass where all the windows are, in effect, solar panels. The Service has ruled that even though such a wall is clearly a "structural component" of the building, the entire cost is still subject to the 30% energry credit. That's a great credit, since it is one that can be used against the AMT (The only thing better is a refundable credit).