You're right Contandino - and it's all unintended consequences. For example: all my glass was just slipped down slots in the doors and windows. Bang one door and every glass pane shook like a minor earthquake - now they are all air-tight with silicone (and silent!) and many windows are draught sealed too - wouldn't mind betting that the number of air changes in the original config would be enough to keep the mould away for 70%+ of the time...