Passive Stack Ventilation

Passive Stack Ventilation systems avoid using electric fans by employing a ‘stack’ effect to draw warm air up from ‘wet rooms’ through ducts. Fresh, replacement air is brought into a property through window trickle vents and wall inlets within the habitable rooms, whilst humidity controls ensure supply always matches demand.

The two main advantages are that it’s silent in operation and has no running costs.

The disadvantages are that the ducts must be near vertical to the ridge or roof terminals, and that the lack of pressure differences affecting airflow might mean it’s necessary to use an open window or additional central fan during warmer weather. This system also wastes heat and may cause draughts, whilst humidity controlled inlets will require extra ventilation when low humidity occurs. Finally, window trickle vents and wall inlets are required.