Hello,
We have a summer cottage (a torp from 1901) where we want to build a bathroom with a shower. The house is closed for the winter when we're not there, and it has worked well for the past 40 years. The water pipes in the house are drained with compressed air, and we have heating cables in the PEX pipes. The toilet is an incineration toilet, so there's no water there either. Right now, we shower in a wood-fired outdoor shower. It's wonderfully nice and is one of the charms of the place, I think. However, not everyone shares my opinion

Hence the bathroom plans.
Now to
the actual question. If you build a bathroom, you need a waterproofing layer. Can't the
waterproofing layer cause problems when winterizing? What I mean is that condensation can form on the wrong side during days when the air inside the house is colder than outside. Could this become a major problem, and if so, what is the best way to solve this? Just don't say heating
Very grateful for your answers, there is a tremendous amount of knowledge here!
Best regards,
Henke