It is 54 degrees outside. Inside my home it is 80 degrees. At night, as the outdoors gets cooler, the inside of my home continues to get warmer, at least with the windows closed. It's a relatively safe neighborhood, but not safe enough to leave a downstairs window open. Opening upstairs windows alone hardly makes a dent in the temperature.
Most of the heat comes from thermal mass I presume, meaning the walls and floors and ceilings store the heat from the day and release it all night, much to my sleeping displeasure. I can't sleep at temperatures above 75 degrees. We have some electronics plugged in, but not too much in that department.
As I walk the dog at 5:30 am, many of the neighbors have their windows closed and the air conditioning running. I reiterate that it is 54 degrees outside.
All of the homes in this development were built about five years ago. I'm sure they meet or exceed all the codes for energy use. And yet many of us are running our air conditioning when it is 54 degrees outside.
All we need to solve this problem is a downstairs window that has both a screen (for bugs) and jail bars (for intruders). The trick is to make the jail bars not look like jail bars, so there is some chance the homeowners association would allow them. The jail bars need not be grey vertical bars. They could be a design that adds a cool and funky look to your portal. For example, the barrier against intruders could be a peace sign, or a happy face, or a pine tree, whatever. And it could be whatever color works with your house.
Obviously this sort of solution is only useful in places and seasons where it is hot during the day and cool at night. But that is a lot of places.
Ideally that window, and a few upstairs, would be motorized and on a remote, so you can close them without getting out of bed if it gets too cold inside.
But my real question is this: If it is colder outside than inside, is there any reason you shouldn't run the air conditioning with your upstairs windows open?