What This Requirement Covers
Non-domestic buildings have ventilation requirements set out in Approved Document F Volume 2 (Ventilation in buildings other than dwellings). The requirements depend on the building use, occupancy density, and any specific pollutants generated by the activities within the building.
Key Requirements
Minimum Ventilation Rates
- Offices: 10 litres per second per person (l/s/p) of outdoor air (CIBSE Guide A recommendation)
- Classrooms: 8 l/s/p with CO2 monitoring to maintain levels below 1000 ppm during occupied periods
- Retail: 10 l/s/p (general retail); higher for food retail
- Restaurants and cafes: 10 l/s/p for dining areas; kitchen extract as specified for the cooking equipment
- Toilets: 6 l/s per WC or urinal extract rate
Ventilation Strategies
- Natural ventilation: Openable windows, trickle vents, and stack ventilation; suitable for buildings with shallow floor plates and low internal heat gains
- Mechanical ventilation: Centralised or localised systems providing controlled supply and extract; required for deep-plan buildings and those with high internal heat gains
- Mixed-mode: Combination of natural and mechanical ventilation, switching between modes based on conditions
- MVHR: Mechanical ventilation with heat recovery; increasingly used in well-sealed non-domestic buildings
CO2 Monitoring
- Approved Document F recommends CO2 monitoring in occupied spaces to verify that ventilation rates are adequate
- A target of 1000 ppm CO2 during occupied periods indicates adequate ventilation
- CO2 sensors should be positioned at the breathing zone (1.2-1.5 m above floor level)
Practical Compliance Tips
- Design the ventilation system to the relevant CIBSE guides (Guide A for environmental criteria, Guide B for HVAC design)
- Commission the ventilation system and provide flow rate measurements to Building Control
- Install CO2 monitors in occupied spaces to verify performance and allow ongoing adjustment
- Ensure natural ventilation openings are adequate for the occupancy; use CIBSE AM10 for natural ventilation design
- Maintain air handling units and filters in accordance with the manufacturer's schedule
- Consider the acoustic impact of mechanical ventilation; noise levels should not exceed the design criteria for the room use
- Provide user controls (openable windows, fan speed controls) where appropriate to allow occupants to adjust their environment