I have been a joiner & boat fitter for 25 years and I have been making double glazed boat windows for 15 years. I have made them for Narrowboats and Wide Beam vessels as a replacement or for new builds. The need for a suitable replacement for “bus windows” is growing.
The main problem with them has always been condensation,which in time leads to linings rotting and steel rusting. Other problems are draughts, ventilation is one thing, unwanted draughts increase heating bills. Double glazing in a boat also provides sound insulation and better security. As all my windows are hand made they can be any shape or size from bow top, round, rounded corners or square.