Yeah that would be an option, but I would call it 'other measures' rather than roof height, because a roof height is never provided on CTBUH. The issue I am raising is it's very often that we can't decide where the roof is. Take the example you gave, Q1. Where is the roof? Is it at the roof of the topmost inhabitable floor? (just over 200m) Is it at the top of the plant room? (a few above that) Or is it at the top of the decorative glass blades that wrap around the top of the building but in no way constitute a structure? (more like 245m) This is why, if you look at CTBUH for Q1, as with just about every building, they don't include a roof height (http://skyscrapercenter.com/building/q1-tower/399). The roof heights are impossible to find. An observatory figure is given for Q1 (235m) which is the height of the floor of the observation deck. No roof height given. Same goes for any other building. They will sometimes give height of highest habitable floor (not the roof, whatever that is), sometimes observatory if there is an ob deck, but they will not even attempt to give a 'roof' height because CTBUH will not even try to define where the 'roof' is. This is why the roof heights for our table are all off sources like Skyscrapercity forums, because CTBUH doesn't actually provide them. As such I'd say we should include a column for other measures and for each building we can include whatever measures we like, so long as a reliable source is found.