As an Aussie who's spent time in Germany in one of these heat waves, this is definitely one aspect. But it's not just "keep the heat in". They are designed with huge thermal mass, so once warm they stay warm for a day or so.
When the heat wave struck, initially that thermal inertia works in your favour as the cool building keeps the interior cool. But after a day or two it heats up. Once that happens, the temperature at night doesn't drop. As you say, ventilation is not good, so the humidity rises too. The thing becomes an overnight sauna.
After one night of this, I went looking for a fan. In my Australian home, every room has a ceiling fan. In this German dwelling (rented by my daughter, an Aussie, for the past few years) there wasn't a single fan in the house, and worse none of the nearby shops sold fans. It looked to me like there was no "social knowledge" of fans or how to handle heat in general. I eventually got a fan off Amazon, who thankfully delivered the next day.
We were also there in another year in winter. These same buildings were amazing the cold. They could maintain a cosy inside temperature with very little extra energy. But geeze, you don't want to be in one in a heatwave that goes on for days.
It's not just cost. Many people in Germany claim they get sick or experience neck pain the instant they stand under an AC. I cannot relate at all and I'm very puzzled, but at the same time I don't want to deny their experience.
I'm Lithuanian and that's my pet peeve when making fun of my culture. I think it comes from homeopathy BS that has roots in Germany.
Funny enough Germans appreciate good ventilation, but here we have following: wind outside - ok, same wind inside (draft) - you killing me. Always wear slippers inside, protect your feet and neck from coldness. Avoid AC at all costs, especially bad if it blows right into your face. Also no fans right into your face or body. Wet hair - do not under any circumstances go outside. Even the most respected people I know fall into this trap.
Possibly some confusion comes from rhinorrhea - people mix up these symptoms with actual disease. And most ironically lack of appropriate ventilation increases spread of respiratory infections.
Last decade+ we had a bit of a HRV fad, wonder if that is reflected in some stats. Anecdotally I heard people shut these off to save power and open window instead...
Portable AC exists and people do use it, but it's loud and awkward with casement windows. This is a bandaid solution at best. Yet, I've seen them sold out in the summer, so people do use them.
That doesn't matter for portable AC. Most people build a plexiglass or foamboard plug for the open window. Some products are sold already set up like this. If you can fit a casement AC that also probably doesn't matter. You can probably remove the window too I'm guessing.
You'll probably want a split unit. Minimum $600 including install in Eastern Europe, but more likely to be over 1k.
Extrapolate salaries, cost of living and that's more like 3k in your money.
That said magic happens when government subsidizes things. Friend spent 8k euro for 10kW solar + 15kWH battery system, of which government reimbursed 7.8k. 1.35k USD for entire system, when you'd pay this much for someone to plug some cables for half a day.
Still doesn’t solve the cost factor. If you don’t have the money you don’t have the money. And if you barely have the money you’re probably going to take the risk because the risk is still very low.
If they are insulated properly (lots of roof insulation) it also keeps the heat out. I'm building a house and last week it reached 32c here, inside got no warmer than 23c on the upper floor. I don't have AC installed yet, just HRV.
