I have never lived without an AC and I get quite ill if I get hot. I'm curious how hot old Paris spaces get in July with no AC? Thinking of renting a space on the fifth floor of an old building in the 9th.
Some days will be quite hot in Paris in July, and if you're used to living with AC it will be an adjustment. I stayed in Paris for a month last July and had to get used to sleeping with a single light sheet, moving as little as possible, and waking up sweaty. Old buildings will likely have poor ventilation, to compound the matter.