Approved Document F Volume 2: Ventilation for Buildings Other Than Dwellings (2021 Edition)
Approved Document F Volume 2 (2021 edition) provides statutory guidance on how to comply with Requirement F1 of Schedule 1 to the Building Regulations 2010 in England. This document, issued by HM Government, took effect on 15 June 2022, replacing previous versions of the ventilation code. It operates under the powers of the Building Act 1984 and addresses the health and safety of occupants by ensuring adequate means of ventilation in non-domestic structures.
The scope of this document encompasses all buildings other than dwellings, including offices, car parks, hospitals, schools, and mixed-use developments. It defines regulatory standards for Extract ventilation, Whole building ventilation, and Purge ventilation. The document is structured into four primary sections: Section 1 covers ventilation provision; Section 2 addresses the ingress of external pollutants; Section 3 details work on existing buildings; and Section 4 specifies requirements for Commissioning and providing maintenance information to building owners.
The technical guidance includes specific performance criteria for indoor air quality, requirements for CO2 monitoring, and installation standards for mechanical systems. It also clarifies interactions with other parts of the building regulations, such as Approved Document B (Fire safety) and Approved Document L (Conservation of fuel and power).
Ventilation Strategy and Performance Criteria
The ventilation strategy relies on a combination of three distinct methods to protect occupant health and prevent the risk of airborne infection and mould growth.
- Extract ventilation: Removing water vapour and indoor air pollutants at source from areas such as sanitary accommodation, washrooms, and food preparation spaces.
- Whole building ventilation: Providing a continuous supply of outdoor air to dilute and remove pollutants not addressed by extract ventilation.
- Purge ventilation: Manually controlled ventilation at high rates to rapidly disperse high concentrations of pollutants, such as fumes from painting or occasional activities.
Mechanical systems must be designed to minimize noise and ensure reasonable access for the replacement of filters, fans, and coils. Guidance in CIBSE’s Guide A and Guide B2 is referenced for calculating ventilation rates when specific pollutant levels exceed standard body effluents.
Standards for Offices and Car Parks
Section 1 provides specific performance-based guidance for office environments and enclosed parking structures to manage bio-effluents and hazardous gases.
- Office Ventilation Rates: Outdoor air should be supplied at 10 litres per second per person or 1 litre per second per m2 of floor area, whichever is higher.
- Intermittent Extract Rates: 15 litres per second per shower or bath, and 6 litres per second per WC pan or urinal.
- Car Park Carbon Monoxide Limits: Ventilation must limit CO to an average of 30 parts per million over eight hours and a peak of 90 parts per million over 15 minutes.
- Printer Rooms: Rooms containing printers and photocopiers in use for more than 30 minutes per hour require an extract rate of 20 litres per second per machine.
Indoor Air Quality and CO2 Monitoring
New buildings must incorporate means of monitoring indoor air quality in specific occupiable rooms, typically through the use of Non-dispersive infrared (NDIR) CO2 monitors.
- Target Locations: Occupiable rooms in offices, gymnasiums, theatres, public houses, and rooms where aerosol-generating activities occur.
- Exemptions: Monitoring is not required for small spaces under 125m3 (or 50m2) or large spaces over 800m3 (or 320m2).
- Monitor Placement: Sensors should be at breathing height, at least 500mm from people, and away from windows or ventilation openings.
- Action Thresholds: Ventilation improvements should be considered if average CO2 concentrations consistently exceed 1500ppm.
Minimising External Pollutants
Ventilation systems must be designed to minimize the intake of pollutants in areas where local air quality is poor or near significant pollution sources like busy roads or combustion plants.
- Intake Location: Air intakes should be positioned as high as possible and on the less polluted side of the building.
- Exhaust Outlets: Outlets must be downwind of intakes and should not discharge into courtyards, enclosures, or architectural screens.
- Air Quality Limits: Document Table 2.1 specifies exposure limits for Nitrogen dioxide (200µg/m3 1-hour average) and Carbon monoxide (10mg/m3 8-hour average).
Work on Existing Buildings and Commissioning
When building work affects ventilation in an existing building, such as replacing windows or adding extensions, the final performance must not be less satisfactory than before the work.
- Replacement Windows: New windows must include Background ventilators (trickle vents) at least equivalent to those in the original windows.
- Minimum Equivalent Area: If the original vent size is unknown, occupiable rooms require a minimum 2500mm2 equivalent area for floor areas up to 10m2.
- Regulation 44: Fixed mechanical ventilation systems must be commissioned by testing and adjusting to ensure performance objectives are met.
- Regulation 39: Building owners must be provided with a log book and written guidance on operating and maintaining the ventilation system within five days of work completion.
Frequently Asked Questions
What is the effective date of Approved Document F Volume 2 (2021)?
The document took effect on 15 June 2022 for use in England and does not apply to work where a building notice or full plans were submitted before that date, provided work started before 15 June 2023.
What is the minimum ventilation rate for an office space?
Outdoor air must be supplied at whichever is higher: 10 litres per second per person or 1 litre per second per square metre of floor area.
Are CO2 monitors required in all rooms of a new non-domestic building?
No, they are required in specific occupiable rooms like offices and gyms, provided the room volume is between 125m3 and 800m3.
What are the ventilation requirements for enclosed car parks?
Ventilation must limit carbon monoxide concentrations to 30ppm over an eight-hour period and 90ppm at peak areas like ramps and exits.
Do I need to install trickle vents when replacing windows in an office?
Yes, if the existing windows had background ventilators, the replacements must have vents of at least the same size. If the building's airtightness is increased, ventilation provision must not be worse than before.
Who is responsible for commissioning the ventilation system?
The person carrying out the work must commission fixed mechanical systems and provide a notice to the local authority confirming it was done in accordance with approved procedures.
How does the document define an occupiable room?
It is a room in a building other than a dwelling that is occupied by people, such as an office or classroom, excluding bathrooms, sanitary accommodation, and storage areas.
What is the extract rate for a bathroom in a non-domestic building?
Bathrooms and sanitary accommodation require an intermittent air extract rate of 15 litres per second per shower or bath and 6 litres per second per WC or urinal.
