Geometry of space
Good room height – at least 2.5m/8.2ft. and preferably 2.7m/8.9ft. or more. Single sided ventilation – the room depth should not exceed 2.5 times the room height, and never more than 10m/33ft. 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.
Highly placed openings/windows in the facade - preferably 2m/6.5ft 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 400-600mm/15.7 - 23.6in. A window width of approximately 1.2-1.4m/3.9 - 4.6ft. is often optimal, since often you need two window actuators if the width exceeds 1.2-1.4m/3.9 - 4.6ft. (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.
Specifically for supplementary mechanical exhaust
- In most cases the capacity of the exhaust should be at least the minimum required air change.
- The exhaust should be controllable by variable speed.
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