I've had the cellulose insulation done by TCL and I've also had exhaust fans installed to suck cool air from outside into the bedrooms at night, and in the stairwell, to vent hot air out - a lot of hot air rises and used to get stuck there. I'm not the sort who would have the aircon on every day as a matter of course, but even then, both methods of heat control have enabled me to reduce my aircon use even more, quite significantly in fact.