That's weird: in Denmark, I guess temperature would go above 19 degrees about 6 months a year. That means that buildings are built with the expectation of being warmed...
I might be in for a surprise, but I don't think there has been a year where the temperature has been above 19 degrees for six months of the year. I'm curious if you have a source on that?
That doesn't seem strange to me. At even lower temperatures, water pipes will burst, so you have to heat it at least a little in winter. Waste heat from humans might be enough to avoid freezing temperatures, but then humans also produce a lot of humidity, causing mold.