A room can be ventilated very quickly with the window and door – preferably located opposite each other – fully open. This is the most effective and – in terms of energy – economical method of ventilation if the time is strictly limited to a few minutes.
In older buildings, basic ventilation takes place via leaks and draughty windows. Even without opening windows, there is an uncontrolled exchange of air in the heated rooms which is often associated with high energy losses.
Modern buildings are made as airtight as possible. For this reason, user behaviour in new builds and in houses that have undergone energy-efficient modernisation must be changed so as to consciously replace used air with fresh air and to prevent warm, moist room air from causing structural damage and mould.
Windowless inner rooms should have a possibility for ventilation (shaft ventilation, fan ventilation). If this is not provided, the used and malodorous air can reach adjoining living areas. This unpleasant effect can be further exacerbated by unfavourable wind conditions.
Moisture damage: In interior kitchens and bathrooms, there is also the risk of moist air condensing on the cold surfaces of components and causing moisture damage.