Comment by macNchz

While it's totally possible to build competently, my impression is that, in the US at least, there are tons of existing houses—built roughly between the 70s (energy crisis) and the mid-2000s when ventilation requirements became more common in building codes—that are fairly tightly sealed but lack any sort of real ventilation systems beyond like, kitchen and bathroom exhaust fans.

Having grown up and lived primarily in (uncomfortably!) drafty old houses, I've noticed the phenomenon ever since I was little kid because they have a distinctive stuffiness and smell of furniture/carpet/plywood even if nothing inside is actually new. I think many people are just used to it/consider it a normal smell of a house because so much of the housing stock is in this category.