Paris is having cold weather right now, and it's even supposed to snow today. I walked by the window to my closet and such a blast of cold air hit my bare legs that I pulled open the curtains to see if the window was open. It was shut, but down the long central opening and under the window, a biting draft still whistled through. Ah, Paris windows!
They look lovely. In my building, like other Haussmannien buildings that make up the classic image of Paris, most of the windows are actually doors. They are built for a temperate climate and don't work well in very hot, very windy, or very cold weather. They're not easy to keep open, or to keep shut!
In the summertime, when it's hot, you want to leave them open. Because you won't have air-conditioning. Unlike American cities, Paris has few insects and you don't need screens. What is so pleasant as a summer's day? But here the first problem arises. How do you keep the windows open? The bottoms of the windows are several inches above the floor, so you can't use a doorstop. The least breeze slams them shut. On a windy day, we resort to standing furniture around the windows on either side so they don't slam so hard they break.
In the winter, you have the opposite problem. It's hard to keep them shut tight. You can hear them rattling whenever there's a storm. Those big central openings on every window in a room leave a lot of chinks for freezing gusts to howl through. Luckily, really cold weather in Paris is rare.