@Benji @JonKramer Yes, that is the natural humidity if you live in a wind tunnel. At the minimum have a steamer on at night, or you are a covid magnet. We, in Canada, usually have sealed windows. In fact, the new super houses need an energy air exchanger to stop the windows from raining.

@hasmis @JonKramer I deleted my post as I understood your point mid-way. :) need good windows/ insulation to control indoor humidity, otherwise the moisture content (vapor) will be the same as outside and produce drier air inside.

@Benji @JonKramer For the old windows, I used to use that 3M shrink plastic over the frames. Then you can just peel it away in the Spring.