I have strong fan blowing air out of my bathroom, but it's connected using flexible duct from the shower ceiling and then to the outside, vent being fitted in the soffit. But both flexible ducts build tremendous amount of mould.
Is there a way to prevent that from happening? I've noticed it doesn't build up on plastic elements and I started thinking about building duct from PVC elements, but that's higher wizardry challenge taking layout into account.
I was looking for something covered with copper, but there are only very expensive medical grade ducts available, so that's not option either.
Really open to ideas.