Tall steel-and-concrete buildings are still structurally sound with all the facade torn off. (After all, they were structurally sound before the facade went on.

Tall steel-and-concrete buildings are still structurally sound with all the facade torn off. (After all, they were structurally sound before the facade went on.) There'd be plenty of light and fresh air for these "indoor houses" — at least the ones around the outside — if this was done. If you want even more light and air, design office towers to have some extra "wasted" central space, beyond just that needed for an elevator shaft and plumbing — i.e. make them into squared-off toruses. Then, post-facade-stripping, it won't be dark in the middle, either. Or just build office towers that are long and narrow, rather than square, such that if you convert them into residential, you get functional "commie block" architecture where every unit gets not only a window, but a balcony.