I live in the Netherlands. My apartment has two floors. The upper floor is basically a greenhouse, so 40C is absolutely normal if I close the windows. During the summer I always keep at least one window open, which cools down the house to around 30-35C. This sucks during summer but during winter it's a blessing because I can have 30C on a sunny day even if it's 0C outside. The only drawback is that the windows are very old so in winter that heat escapes immediately once the sun is gone. HOA has been planning window replacement for years already.
The lower floor has windows facing north so it's always much cooler there. I've never seen it reach more than 30C, which was in the middle of a heatwave, usually it keeps 25C during summer.
The lower floor has windows facing north so it's always much cooler there. I've never seen it reach more than 30C, which was in the middle of a heatwave, usually it keeps 25C during summer.