Another factor is content. I had a conference call this morning to discuss a potential LEED project (the USGBC's certification system for sustainable buildings). Part of the materials & resources aspect of LEED looks are regional content, or building materials that are completely sourced from within 500 miles of the jobsite. That doesn't just mean where it's "made" - that means where the constituent parts come from. For concrete, that means documenting where the sand, gravel, and cement all come from. For wood, that means where the tree came from and where it was processed. They exclude mechanical and electrical systems from these credits because it is simply impossible to document all the hundreds of pieces of steel, copper, plastic, and electronics that go into our systems. If you did succeed in such a documentation process, though, I bet it would be an interesting read. How much steel was recycled content and how far the steel traveled from recycling bin to jobsite; how much steel was new material and how far it traveled from the ground to the site; same for copper tubing and wiring; and even where all the various printed circuit boards, components, and miscellaneous bits and pieces came from...