Most Canadians know they should close their windows when the AC is running, but they make a massive, expensive mistake during those transition weeks or cool summer nights when they try to let the natural breeze cool the house down.

  
If you just crack open a window in the room you are currently sitting in, the air barely moves. You aren't actually cooling the house; you're just letting the humidity creep in.

The Tip: You need to create a high-velocity cross-breeze using thermal siphoning (the "chimney effect").

1. Downstairs/Windward Side: Open the windows on the lowest level of your home (or the side where the wind is actively blowing against the house) only a tiny crack—about 2 inches.

2. Upstairs/Leeward Side: Go to the highest level of your home (or the side facing away from the wind) and open those windows wide.

3. The Physics: Because hot air naturally rises, it gathers at the top of your house. By opening the top windows wide and the bottom ones only a crack, you create a low-pressure vacuum. Cool air is aggressively sucked in through the small ground-floor openings like a jet stream, while the hot, stagnant air is rapidly pushed out the top.

 

It behaves like a free, whole-house fan. If you set this up at 8:00 PM on a cool evening, you can drop your home's temperature by 3°C to 4°C in under an hour without touching the AC. Just make sure to shut them tightly by 8:00 AM the next morning to lock that free cool air inside!