I do not have air conditioning, and I have no immediate plans to get any. This is no trouble 10.5 months a year, but warm nights in late July to August can get annoying. Has anyone tried those aluminum foil- like thermal shields for the attic to reflect heat? How about the solar powered attic fans? I have an old house near a river, and it has high ceilings, tall windows and ceiling fans, if that makes a difference to the effectiveness of these things.
best is to have the attic floor well insulated and the attic be well ventilated.
vents in the roof or wall up high to let out hot air. vents in the soffits to allow cooler air in.
at night draw in cool air with your ceiling fans. in the day turn the fans off, close the windows and pull down the shades on the south side. open the windows during the day when the inside temperature is equal to or greater than the outside temperature. i’ve cooled my living space like that, even a flat in the big city; it will seem strange having the windows closed on a hot summer day but i could have my space cooler than the outside until 4PM (after the usual hottest part of the day).
passive vents in the attic can work well if large enough. fans can be easily mounted in the end walls.
When choosing your insulation, get an expert to tell you both numbers for the different types of insulation, though: there is the k number, which means how well the material insulates; and the time lag number, which means how many hours it will take for heat/cold to pass through the insulation. Different materials (sheep wool, shredded paper, fiber mats…) can have similar k numbers, but different time lags. Ideally you want 9-12 hours, which means that you open all windows at night to let cool air in, and close the shades to keep the heat outside and the coolness inside during the day.
Reflective shades during the day can also help quite a lot with keeping things cool.
An additional measure is the roof itself: either paint it white to reflect the sun, or make it green by putting plants there. (Unless your roof is slanted). (That is the cheaper option instead of installing solar panels, since this is impossible in the US way of financing houses).