>>who, anywhere, wouldn't do this ?

FWIW - Many places/people. Most, in my anecdotal experience.

- I've seen numerous condos in north america and Europe that do not have effectively openable windows, certainly not in quantity to properly vent the entire unit. So you couldn't if you wanted to.

- Some cultures have very differing perspectives; where I'm from, interior "Cross-winds" are deemed to be deadly. You will NOT open two windows at the same time anywhere in the house, ever, period. If any window happens to be open and a kid opens the front door, they'll be yelled at to close it ASAP lest... I dunno, something about their lower back?

- But most people I've spoken to / lived with, across countries and continents just don't bother / it doesn't occur to them. It's not a thing (this includes living with three host families in Minnesota in the 90's - none of them opened their windows much if at all, trusting their HVAC to take care of them. Two of them were medical professionals.

> where I'm from, interior "Cross-winds" are deemed to be deadly.

In Romania, too, popular belief considers drafts to be a dangerous cause of illness, but at least in my own experience, opening all the windows in the morning is an exception. Airing out the house daily in winter is seen as a healthful thing to do by many if not most families... but of course once all the windows are closed again, there shouldn't be the slightest hint of a draft anywhere in the house.

> interior "Cross-winds" are deemed to be deadly

Interesting! Never heard this before. Where are you from, if I may ask?

I think this article describes it well, including the absolute cultural prevalence, belief, and influence :). It is written in regard to a single country (Croatia) but applies to Balkans and few other parts of Europe as well:

https://zablogreb.wordpress.com/2012/12/26/propuh-or-the-gre...

In Sweden too, at least a generation back or two, it was like this.

Incredibly interesting, thanks!

Sounds like Eastern Europe to me.

My family members used to yell at me for sitting down on a stone fence or concrete bench, because something something cold stone ... lower back / kidney disease.

The same irrational belief is common in Germany as well. Cold air is thought to cause things like the common cold and bronchitis.

Some people would feel a slight draft indoors and immediately start yelling for the windows to be closed.

I knew a very wealthy guy in Germany who bought a Mercedes 560SEL - at the time, the top-of-the-line model. He ordered it without air conditioning because he didn't want to get bronchitis.

“Es zieht!”

> You will NOT open two windows at the same time anywhere in the house, ever, period.

This makes literally zero sense. It's even stupider than Korean Fan Death.

Oh it really is. I grew up with the bs, and people don't seem to believe you when you tell them that it's no worse than wind blowing on the street.

It's analogous, irrational, and nonsensical from our perspective, so I'd agree.

(I think the article I linked later demonstrates some interesting and radically differing cultural assumptions)

My mother is constantly complaining that apartment is cold, and then I close the window.

>because who, anywhere, wouldn't do this ?

Whoever paying to heat the building in question isn't gonna do this.

Venting significantly reduces the humidity of your air, driving down the heat capacity of it. Meaning you will need less energy to heat up the room.

This thread seems to give a great overview of all interactions: https://physics.stackexchange.com/questions/45349/how-air-hu....

It's actually common part of contracts in Germany that you have to vent at least 10min per day through 2 different rooms etc.

You own link points out that the difference between humid and dry air in terms of heat capacity is a low single digit percent. Unless you can reduce the humidity from "a lot" to "basically nothing" and lose only a couple of degrees in the process (highly unlikely, completely impossible if your method consists of opening windows/doors in the winter) it is going to cost more energy to vent out the humidity and heat dry air than it is to just heat the humid air that's already near temp.

Just because a rental contract includes a clause doesn't make the intentions of that clause consistent with reality.

Furnaces dry out the air. Human activity can contribute moisture to the air. But the net effect is usually to leave the interior air dryer than the exterior air. Depending greatly on your lavatory ventilation.

Where I live, allowing outside air in greatly increases the inside humidity. And I would guess this is true for most people given the widespread complaints of dry winter skin and bloody noses. Which is the product of increased furnace operation.

> Venting significantly reduces the humidity of your air

Even when it's raining outside, etc?

If it's raining, then obviously it's not very cold outside. Unless you're in the habit of cranking your furnace up to tropical temperatures I guess. For me, I keep the temperature above freezing inside but otherwise? I put on a sweater and open the window. It's cheaper, refreshing, and better for the environment. Right now it's 8 C outside; with the window open and a sweater on, I'm as comfy as a clam.

Ok but you must that this is unusual and most people keep their thermostat around 21 C.

I don't know, it's typical for my family. It seems inappropriate to me for people to set their furnace so high just so they can dress like it's summer in the winter.

I have never "cleared the air."

Besides the advantage of air heating (that gives the illusion of reheating the house [1])there are a lot of differences in the way houses are built.

Generally speaking "traditional" houses in Europe (made with brick or stone walls) tend to have rather poor insulation but very high termal mass, as opposed to more modern houses (and to the essentially wood/timber based houses in north America) that have a higher insulation but very low thermal mass.

In high thermal mass houses completely changing the air does not lower that much the temperature as as soon as you re-close the windows the air is re-heated by walls, ceilings and floor radiating the heat they accumulated before.

[1] whilst in reality it only re-heats the air

I live in Canada and keep a window open a crack in winter to vent the place. It is considered highly eccentric.

I know my grandmother did it but people seem to have lost the habit. I’ve only heard of it being widespread in Germany.

I’ve heard this usually described as a German custom “lüften”, conveniently in line with Covid guidance.

Would be interesting to see a world map of daily clear-the-air adoption. I hadn’t heard of it before this year.

https://welcometogermerica.com/2018/12/how-to-air-out-a-room...

Never heard of people doing this.

I've lived in the Twin Cities my whole life and have never heard of or done this.