So, I finally found out the answer to another Weird Italian Thing.
Italian houses all have either wooden shutters or these impenetrable blinds on all their windows. I have blinds, which are the most common thing in this part of Italy.
They're pretty useful, actually. You can put them half way down so when the sun is on you, you can make shade, but also allow some air in. They have slots between them so you can put them down sort of all the way, but not quite and it keeps the zanzare out, and lets some air in. You can put them down all the way when it is really windy or rainy and the weather stays outside.
Sometimes they come with locks, so you can put down the one on your balcony most of the way but leave a little space at the bottom so the cat can get in and out, but burglars can't get in.
But Italians don't use them that way. They just keep them all the way down all the time every single day. There is an apartment building opposite ours that I thought was unoccupied because I have never seen the blinds up on any of the apartments. Then one day, one of them was up, and I could see people having normal life inside. There are 17 windows on that building visible to me now, and only three have the blinds up at ten thirty in the morning.
The blinds absolutely block the light. Completely. They make it as though there is no window in the room. They are a wall, so the rooms must be utterly pitch black inside. And they block the air movement too. So I can't imagine what sort of state the room would be in when it is, as it is now, 29 degrees C. out.
Well, I found out why Italians do this insane thing that makes me worry I live in a country full of vampires.
The sunlight fades the furniture, you see.
And when they tell you that, and while you're blinking at them in wordless stupification at the insane weirdness of Italians, they give you a look that says, "Man, these stranieri are weird!"