If the indoor air temperature at ceiling level is higher than the outdoor air temp, you need to vent your ceiling/attic, somehow... even if it's just a cross-breeze between opposing vents or upper windows. Otherwise, you are living in a Dutch oven.
At night... you've got a usable Temperature Differential? Use natural convection:
Once you have a high vent/window open, after sundown, when ground level air is cooler than your indoor air, bring that cooler air in... keep it cool... bring it in through rooms that get no outdoor sun exposure to their walls, roof, whatever.
[Passive Annual Heat Storage] is something to research for ideas. New or renovating construction... Trombe walls... whole systems using underground airways using the thermal mass of the soil to dissipate heat, return cool air...
Good luck!
