I've seen apartments and office buildings where it's literally impossible to open windows, as well as quite a few where you could only open the windows by a few cm.

I worked in an office building without windows that could open years ago, and I got a headache around 2pm every day. It had some mechanical ventilation, but it's not really the same as actual fresh air. It was by far the most horrible office I've ever worked at.

A lot of people also don't like it when I open windows for a bit to let some fresh air in, even when the air is clearly stale and musty. I don't know why people are so opposed to opening windows. My pet theory is that it's a subconscious psychological connection to a certain piece of software :-)