It's not as straight forward as that. One of the major hurdles AFAIK is that many of those office buildings still has asbestos in them in very significant quant

It's not as straight forward as that. One of the major hurdles AFAIK is that many of those office buildings still has asbestos in them in very significant quantities; the buildings were made before the dangers of asbestos were realized. There was some reasons for leaving it in place, and to be fair a major renovation would have to run into these hurdles either way. But it's probably going to be quite a bit more costly then you're imagining.