With new housing built for optimizing energy intake with three-layer windows and 40cm thick insulation etc, slapping a $200 AC unit in a window seems like a dirty hack to put it mildly. It is common with centralized heating systems, so perhaps next step is to adapt centralized cooling systems. Short term I would put my money on moveable outside shades in front of windows, and large green outdoor plants on the balconies. Would also prefer bright colors on roads and building roofs to reflect light instead of turning it into heat.