There is no simple answer. Economically, the cost per square metre starts to soar once a building passes the 70-story threshhold. Meanwhile, taller and taller buildings are being constructed. Construction would start around 2000 and take an expected four years, developer Bruno Grollo told reporters. The tower would surpass the 452-meter Petronas Towers in K.L., Malaysia, which wrested the world's highest building title from Chicago's Sears Tower in 1996.
People normally feel nervous and get dizzy standing on top of a tall building.
The main reason is that our eyes are not used to seeing objects at a great distance where the floor should be. The resulting confusion in brain signals and general anxiety caused by being in a potentially dangerous situation cause dizziness. Construction workers working on top of tall building would be more at ease when they are accustomed to the height.