Building Regulations Approved Document F sets out the legal requirements for ventilation in buildings across England and Wales. This document supplements the Building Act 1984 and establishes minimum standards for air circulation to protect occupant health and prevent structural damage from condensation. While Approved Document L focuses on sealing buildings for energy efficiency and damp control, Document F ensures that adequate fresh air reaches every habitable space. This may seem contradictory, but both documents work together: Document L controls uncontrolled air leakage while Document F mandates controlled, purposeful ventilation. Understanding these requirements is essential for building design, construction, and home improvement projects.
What Approved Document F Covers and Why Ventilation Matters
Approved Document F is divided into two main sections. Section F1 deals with ventilation within buildings, stating that all properties must have adequate and suitable ventilation for the occupants. Section F2 covers mechanical ventilation systems, requiring that any installed system is properly commissioned through testing and that the building owner receives full operating and maintenance instructions.
The fundamental reasons ventilation matters in buildings include:
- Removing carbon dioxide exhaled by occupants and replenishing oxygen levels in the air
- Extracting moisture from daily activities such as cooking, showering, and laundry to prevent condensation
- Diluting and removing airborne pollutants including dust, bacteria, and volatile organic compounds from furnishings
- Controlling humidity levels to prevent mould growth and timber decay in building structures
- Removing smoke, odours, and other airborne contaminants from specific rooms
Without proper ventilation, modern airtight buildings suffer from condensation problems that lead to rot in roof timbers, damp walls, and poor indoor air quality. The official Approved Document F publication provides full technical details on compliance requirements for all building types.
The Three Types of Ventilation Required in Dwellings
For residential buildings, Approved Document F identifies three distinct types of ventilation that must be provided. Each serves a different purpose and understanding them is fundamental to designing systems that maintain healthy ventilation requirements for buildings of all types.
Whole Building Ventilation
This is the background ventilation that runs continuously to provide fresh air throughout the entire dwelling. It ensures the air within the building is constantly changed, even when windows are closed and rooms are unoccupied. Whole building ventilation can be achieved through natural means such as trickle vents in window frames, or through mechanical systems such as continuous mechanical extract ventilation (MEV) or mechanical ventilation with heat recovery (MVHR). This type of system can be turned down when the building is unoccupied.
Extract Ventilation
Extract ventilation removes pollutants and moisture at their source before they spread through the building. This system is essential in rooms where high humidity or pollution is generated, such as bathrooms, kitchens, and utility rooms. An extractor fan in a bathroom pulls moist air outside, reducing condensation on walls, mirrors, and windows. A cooker hood in a kitchen removes cooking odours, steam, and airborne grease particles. Extract ventilation typically operates intermittently at higher flow rates than background systems, activated manually or by humidity sensors.
Purge Ventilation
Purge ventilation provides a means of rapidly removing large volumes of stale or polluted air from a building. This is the simplest form of ventilation and often requires no mechanical equipment. Opening windows or external doors creates a cross-flow of air that quickly clears smoke, strong odours, or excessive humidity. Purge ventilation is also useful for cooling during hot weather. The regulations require that all habitable rooms have some form of openable window or equivalent purge provision.
Natural Ventilation versus Mechanical Ventilation Systems
Approved Document F recognises both natural and mechanical approaches to achieving required ventilation rates. The choice depends on building design, location, and the specific requirements of each space. Many modern buildings use a combination of both approaches.
| Ventilation System Type | How It Works | Best Suited For | Energy Impact |
|---|---|---|---|
| Natural ventilation | Uses windows, doors, and trickle vents to allow air movement driven by wind and temperature differences | Homes in areas with good outdoor air quality and moderate climate | No electrical consumption, but uncontrolled heat loss in winter |
| Mechanical extract (MEV) | Central fan extracts air from wet rooms via ductwork, drawing fresh air in through background vents | Homes requiring reliable, controllable ventilation in all weather | Low energy use; some heat loss through extracted air |
| MVHR | Supplies filtered fresh air and extracts stale air while recovering heat from the outgoing stream | Airtight, highly insulated homes where heat retention is a priority | High efficiency; recovers 80-95% of heat |
| Positive input (PIV) | Fan supplies filtered air into the building, pushing stale air out through vents | Homes with persistent condensation or humidity problems | Moderate energy use; can reduce heating demand |
Where mechanical ventilation is installed, Part F2 requires full testing and submission of commissioning results to the local authority within five days of the final test. The installer must provide complete operating and maintenance instructions. For properties with pitched roofs, proper roof ventilation systems must be integrated to prevent condensation in roof spaces that can cause timber decay.
When choosing a ventilation strategy, builders must also consider energy efficiency measures because the ventilation system itself affects the building’s overall heat loss. The regulations require that ventilation is controlled so it does not adversely affect energy performance.
Ventilation Requirements for Non-Dwelling Buildings
Non-dwelling buildings such as offices, retail spaces, leisure centres, and commercial kitchens have additional ventilation considerations. The presence of more occupants, heat-generating equipment, and specific activities creates greater demand for fresh air supply and temperature control.
For non-dwelling buildings, Approved Document F works alongside Approved Document L2a, which covers the conservation of fuel and power in buildings other than dwellings. Cooling becomes a significant factor in commercial buildings, and the ventilation system must maintain comfortable conditions during peak occupancy.
Regardless of the building’s use, the regulations require attention to the following points:
- Air continuously circulated through air conditioning or mechanical ventilation must meet quality standards
- The potential for Legionnaires disease must be assessed, particularly in water-based air handling systems
- All ventilation systems must be designed for easy repair and maintenance access
- Cooling loads must be calculated properly and integrated with the air conditioning strategy
Designers on commercial projects should refer to CIBSE design guidance documents which provide detailed methodologies for calculating ventilation rates and designing compliant systems for different occupancy types.
Ventilation in Offices and Workplaces
Offices and workplaces are covered by specific regulations within Approved Document F, and these extend to associated areas such as leisure centres, commercial kitchens, storage cupboards, changing rooms, washrooms, and toilet facilities. People working in these spaces require levels of ventilation similar to dwelling occupants, but the methods of achieving compliance differ.
The regulations permit several approaches to achieving required airflow rates in workplaces:
- Through provision of natural ventilation where the building design and location allow adequate fresh air intake
- By following guidelines in CIBSE Manual AM13:2000 and CIBSE Guide A and B2, which provide ventilation rate calculations based on occupancy and room function
- Through installation of a mechanical ventilation system demonstrated through testing to meet required air quality and moisture levels
Open-plan offices require higher ventilation rates than cellular offices due to higher occupancy density. Meeting rooms and areas with high occupant turnover need additional purge capacity. The regulations require that building insulation upgrades and other retrofit measures do not compromise existing ventilation performance.
Alterations to Existing Buildings and June 2022 Updates
Works on Existing Properties
Where alterations are carried out on an existing building, the regulations require that existing parts retain their current ventilation performance. These levels must not be reduced by new building work or improvements. Window replacement is one of the most common improvements affecting ventilation. Any new windows must comply with Approved Documents L and N, and should include trickle vents unless existing ventilation levels are demonstrably unaffected.
Builders working on existing properties must consider building codes and compliance standards when planning ventilation modifications to ensure all work meets current requirements.
June 2022 Updates to Approved Document F
On 15 June 2022, significant updates to Approved Document F came into effect. These changes were introduced to align the regulations with new net zero requirements and help meet the 2025 Future Homes Standard. The key changes include:
- Simplification of ventilation requirements across all building types, making compliance clearer
- Alignment of air tightness testing with overall system performance
- Specifications may differ depending on how buildings and areas are used
- Focus on air quality to ensure it is as clean as possible with no harmful pollutants
- CO2 monitors required in office buildings where airborne infection risk is significant
- Minimum air supply rate of 0.5 litres per second per square metre for mechanical ventilation in common areas and offices
- Recirculating air systems must filter or clean the recirculated air
- Trickle vents required when windows are replaced in domestic properties unless ventilation is unaffected
- Homeowner guidance on why ventilation is important when systems are installed
- Commissioning sheet and system design documentation for the homeowner
- Official checklist for builders to assess how past and future works affect ventilation
These updates represent a significant shift towards recognising indoor air quality alongside energy efficiency. As with all Building Regulations Approved Documents, it is essential to reference the most current regulations before commencing any building work. The official Approved Document F can be downloaded from the UK Government website, and local authority building control departments can provide guidance on specific compliance requirements.