Ventilation system types and design flexibility

This ventilation strategy can be delivered by a natural ventilation system or a mechanical ventilation system or a combination of both (i.e. "a mixed mode" or "hybrid" ventilation system). For mainly naturally ventilated buildings, it is common to use a combination of ventilators to achieve this strategy (e.g. for dwellings it is common to use intermittent extract fans for extract ventilation, trickle ventilators for whole dwelling ventilation and windows for rapid ventilation). For mechanically ventilated or air conditioned buildings, it is common for the same ventilators to provide both local extract and whole building/dwelling ventilation and, for buildings other than dwellings, to provide rapid ventilation as well. Whilst it is not a requirement of the regulations, where fans are installed, it is advisable to fit anti-backdraft shutters to the appliance.