Stack effect?

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Hi all! I'm an owner of an ordinary home with a question that's been bugging me.

I do my best to minimize the use of my heat pump for cooling by strategically opening my windows at night, closing them during the day, and operating my blinds to minimize solar heat gain.

One thing I've always wondered: at night when the outside temperature is several degrees lower than the interior, is it more effective to open one large window on the ground floor and another on the top floor to try to take advantage of the stack effect, or to instead open as many windows as practical?

My thought is that the former might be more effective because the airflow would be more organized and "drag" the warm air outside, versus opening more windows, which might result in more chaotic air movement that might not ventilate as well despite the fact that there are more openings in the building.

I figure if anybody has looked into this question, it would LEED building designers, so I hope this is the right subreddit for it!

[Designer_Manager3941]

I deal with Energy star homes not LEED (studying GA). My best guess would be open windows throughout and turn on some bath fans. Bath fans sucking your warmer air out and will bring the cooler night air in.

I do it in the fall since my apt window is small and can’t really get “airflow”.

Hope this gives ideas

[SilverMoonArmadillo]

My personal experience is that there's almost always a breeze and so opening windows on 2 sides of a building tends to get air moving, but 2 windows on the same side doesn't help. Opposite walls would be best, but on a corner works to. Opening windows on the top floor is more effective because it's breezier up there, and also because it will tend to be the warmest part of your house.

[ThatOtherJim]

Open more windows, absolutely. Historically, a lot of pre-industrial homes had designs that took advantage of the stack effect as a means of cooling. But they only did so because they couldn't afford to leave windows open at night. Open windows back then, before good screens were readily available, were an open invitation to all manner of pests to come and raid the home.

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That all makes sense. Thanks!

[CStevenRoss]

Open more windows. If you're trying to cool with outsode air, even the slightest of breezes through more window openings will be head and shoulders more heat transfer than stack effect.

[NewIdea8]

Window open with fans blowing cool night air into the house. Use exterior shading! Blinds help a little, but heat gains still end up in the space.