I'm imagining that there's an element of truth to what you say - but one would guess that the slabs for these houses are still made up of concrete, not to menti

I'm imagining that there's an element of truth to what you say - but one would guess that the slabs for these houses are still made up of concrete, not to mention the driveways (as well as all the other infrastructure running to said houses - sidewalks, curbs, etc). Apartments being smaller, I would be surprised if there's a huge difference in materials and construction energy input per capita between apartment living and house living. The economies of scale of an apartment building are pretty big; for example, it has one roof and one slab (obviously way bigger). It's of course possible to construct all sorts of weird versions of this comparison (tiny houses vs McMansions, ultra-modern mid-rises made from timber, etc. etc). I suspect it's all moot given that transport is such a substantial component of energy use and these houses/apartments should last a long time.