Inching towards sustainability: Developers are sort of inching forwards on this, you know:  first they put a windmill on top of something and then put a green roof, and gradually little incremental improvements are made, and clearly something like Bed-Zed is more dramatic because it’s trying to really build a zero energy development from scratch in all respects and it would be really good to see something like that.  This transcript is part of King's Cross Central - A Development Challenge