@Mark116 : I may agree, and Dept. of Energy may recommend 78F, but the supermarket around the corner, and every office building, museum, and other institution is at 65F. (And be sure: the Jewel-Osco two blocks away is a metal box that is leaking energy at an unbelievable rate.)
That said, 72-78F during these events would probably not, from an engineering standpoint, be ideal as a target at all; in environmental conditions such as those normal in Singapore, which is what we're seeing Chicago and other cities become like during these extreme events, it's much cheaper to cycle air conditioning for 18 hours/day than for 6 hours.
A key factor maintaining a dry environmental envelope/shell at the outside edge of the house, so that humidity cannot soak into the building materials and act as a painfully effective head conductor.
We are also just seeing air conditioning systems that are able to adjust / cycle power effectively come onto the market, in place of current systems that are essentially on/off with varying fan speed -- that should let us eek out another 10-30%, eventually.
Overall, it's going to take a lot of small-scale structural understanding of existing buildings to survive; in the case of Chicago's mostly post-fire, brick construction units, a constant series of 1-2 extreme events/year over a decade or so is going to do a lot of damage to buildings where people aren't paying attention.
We had plaster falling, condensation on structural beams and pipes creating water flows through the structure, and a host of other issues that, against the background of Chicago deploying mobile cooling units and tens of deaths, drove home exactly how serious such events are, and what they can do.
