Natural ventilation design
Natural ventilation design guidelines and thumbs of rules to help you design the perfect natural ventilation solution.
Natural ventilation advantages
Geometry of space
- Good room height – at least 2.5 m and preferably 2.7 m or more.
- Single sided ventilation – the room depth should not exceed 2.5 times the room height, and never more than 10 m.
- Cross ventilation - the room depth should not exceed 5 times the room height.
- Stack ventilation – the distance from the facade to the rooflights should not exceed 5 times the room height.
Window opening
- Highly placed openings/windows in the facade - preferably 2 m or more above floor level and with sufficient clearance between the top of vent and ceiling for inward opening vents so as not to limit the achievable opening area.
- Bottom hung inward windows or top hung outward openings in the facade.
- Window height, facade: Approximately 400-600 mm.
- A window width of approximately 1.2-1.4 m is often optimal, since often you need two window actuators if the width exceeds 1.2-1.4 m (subject to window profile material and type, due to frame flex with single pull point).
- Openings evenly distributed.
- Bottom hung inward windows or top hung outward openings in the facade.
Other natural ventilation guidelines
- Optimised Natural night cooling.
- Preferably include thermal mass for optimum benefit of night cooling.
- User control e.g. timed override facility by local keypads.
- Preference for cross ventilation, stack ventilation or hybrid ventilation in high occupancy spaces e.g. in classrooms.
- Preferably a minimum 7m3 per person in e.g. classrooms.
- Maximum air changes.
Winter: Approximately 2.5-3 h-1 (average during occupied hours).
Summer: Workstations: 4-6 h-1 can easily be accepted.
Atriums and similar transient spaces where people stay for shorter periods: 10–15 h-1 can be accepted.
