[Taf]

When our walls had cavity insulation fitted, and double glazing added, the coldest surfaces, such as the bathroom mirror, always got condensation. I'd rather that, than damp walls. Airing the rooms sorts out excess humidity.

After fully tiling the bathroom one Spring, it took months for the humidity levels to drop to "normal" because the only path out for the moisture was via the grouting. I was told years later that it best practice not to grout immediately, but to allow the adhesive and the walls they are fitted-to, to dry.