Boats keep water out by design, but unfortunately that makes them very good at keeping moisture in. On our boat Ti-Gitu in cooler weather when we have a heater on, the windows run with water, the lockers become damp and in the corners of lockers, black mould will appear. This often happens aboard boats stored ashore for the winter but is especially true in a boat that is being lived aboard for extended periods of time.
The average human loses approximately 800ml of water through breathing and the skin each day. Working or exercising hard an average person sheds between 0.8lt to 1.4lt per hour. Evaporation from cooking and places such as the bilges, or cleaning work surfaces, washing and showering all adds to the moisture in the atmosphere. Obviously this moisture has to go somewhere and when it is cooler outside it will condense inside onto windows and then run down to find its way behind panelling and into lockers.
Window experimentation
Our yacht is built from steel and despite having plenty of insulation and ventilation by dorade vents and opening hatches to keep a good air flow through the vessel with two of us permanently living aboard the moisture can be considerable.
‘When we have a heater on, the windows run with water, the lockers become damp and black mould will appear’
I experimented on our windows with a form of plastic film double
