6.1 This Approved Document sets out guidance for the following range of building types and uses:
a. offices – paragraphs 6.9 to 6.17;
b. car parks – paragraphs 6.19 to 6.22;
c. other building types – paragraph 6.18.
6.2 The ventilation provisions will not necessarily meet cooling needs. Guidance on limiting solar gains in summer to control overheating is considered in Approved Document L2A Conservation of fuel and power in new buildings other than dwellings.
6.3 Provision should be made to protect the fresh air supplies from contaminants injurious to health. Guidance on the siting of air inlets is provided in Appendix D.
6.4 Guidance on design measures to avoid legionella contamination, including design features not related to the ventilation of the building, is given in the HSE document Legionnaires’ disease: the control of legionella bacteria in water systems (see paragraphs 79 to 144). Further guidance may be found in CIBSE TM13 Minimising the risk of Legionnaires’ disease and in BSRIA Application Guides AG19/2000, AG20/2000 and AG21/2000.
6.5 Guidance on recirculated air in air- conditioning and mechanical ventilation systems is given in HSE document L24 Workplace health, safety and welfare, Workplace (Health, Safety and Welfare) Regulations 1992, Approved Code of Practice and guidance (paragraph 32).
Access for maintenance
6.6 Reasonable provision would be to include:
a. access for the purpose of replacing filters, fans and coils; and
b. provision of access points for cleaning duct work.
6.7 In a central plant room adequate space should be provided as necessary for the maintenance of the plant. Where no special provision is required, the requirement could be satisfied if 600 mm space is provided where access is required between plant and 1100 mm where space for routine cleaning is required (see Diagram 5). These figures are the minimum necessary and additional space may be needed for opening of access doors, withdrawal of filters, etc. Further guidance for more complex situations can be found in Defence Works Functional Standard, Design & Maintenance Guide 08: Space requirements for plant access operation and maintenance. Further guidance for the cleaning of ducts is provided by CIBSE Ventilation hygiene toolkit and HVCA TR/19 – Guide to good practice – Internal cleanliness of ventilation systems.
Diagram 4 Spaces for access
Introduction to provisions
6.8 This Approved Document shows four ways of complying with the ventilation requirements of the Building Regulations:
a. providing a ventilation system which meets the air flow rates set out in paragraphs 6.9 to 6.13; or
b. following the system guidance set out in paragraphs 6.14 and 6.15; or
c. following the system guidance set out in paragraphs 6.14 and 6.15; or
d. using other ventilation systems, provided it can be demonstrated to the Building Control Body that they satisfy the Requirement, e.g. by showing that they meet the moisture and air quality criteria set out in Appendix A.
Table 6.1a Extract ventilation rates
Table 6.1b Whole building ventilation rate for air supply to offices
Table 6.2a ventilation for offices with natural air supply – ventilation provisions
Table 6.2b Ventilation for offices with natural air supply – location of ventilators in rooms
6.9 The performance will be achieved by ventilation which provides the air flow rates set out in paragraphs 6.10 to 6.13. The air flow rates specified are for the installed performance.
6.10 Extract to outside is required in all office sanitary accommodation, washrooms and food and beverage preparation areas. In addition, printers and photocopiers in substantial use (greater than 30 minutes per hour) should be located in a separate room (to avoid any pollutants entering the occupied space) and extract provision installed. The extract flow rates should be no less than those specified in Table 6.1a.
6.11 The whole building ventilation rate for the supply of air to the offices should be no less than that specified in Table 6.1b.
6.12 Purge ventilation provision is required in each office. The total ventilation should be sufficient to reduce pollutants to an acceptable level before the space is occupied. The purged air should be taken directly to outside and should not be re-circulated to any other part of the building.
6.13 The outdoor air supply rates in Table 6.1b for offices are based on controlling body odours with low levels of other pollutants. Where there are significant levels of other pollutants, adequate outdoor air supply can be achieved by following the calculation method provided in CIBSE Guide A.
Natural ventilation of rooms
6.14 The air flow rates specified in Tables 6.1a and 6.1b can be provided by a mainly natural ventilation system by following the guidance in Tables 6.2a, 6.2b and 6.2c. A wide range of natural ventilation systems for providing whole building ventilation is given in CIBSE Application Manual AM 10: Natural ventilation in non-domestic buildings.
Mechanical ventilation of rooms
6.15 The requirement will be satisfied by following:
- the air flow rates set out in paragraphs 6.9 to 6.13; and
- the location guidance in Table 6.2b for extract ventilation; and
- the control guidance in Table 6.2c for extract ventilation.
6.16 As an alternative to paragraphs 6.9 to 6.13 the requirement will be satisfied by following the relevant recommendations of:
- CIBSE Application Manual AM 13: 2000: Mixed mode ventilation;
- CIBSE Guide A and CIBSE Guide B.
Ventilation of other types of building
6.17 The requirement will be satisfied by following the appropriate design guidance for the other buildings given in Table 6.3. In addition to the guidance documents listed, it should be noted that the Workplace (Health, Safety and Welfare) Regulations 1992 apply to most places where people work. A short guide, INDG244, is available from the HSE and at: www.hse.gov.uk/ pubns/indg244.pdf.
Table 6.2c Ventilation for offices with natural air supply – controls for ventilators in rooms
Table 6.3 Ventilation of other buildings and spaces
Table 6.3 Ventilation of other buildings and spaces
Ventilation of car parks
6.18 The requirement will be satisfied for car parks below ground level, for enclosed-type car parks and for multi-storey car parks if the mean predicted pollutant levels are calculated, the ventilation rate is designed and equipment is installed to limit the carbon monoxide to:
a. an average concentration of not more than 30 parts per million over an eight hour period; and
b. peak concentrations, such as by ramps and exits, of not more than 90 parts per million for periods not exceeding 15 minutes.
6.19 Note that Approved Document B also includes provisions for the ventilation of car parks for the purpose of fire risk management.
Alternative approaches for ventilation of car parks
6.20 As an alternative to paragraph 6.18, the following guidance would satisfy the requirement:
a. Naturally ventilated car parks. The provision of well-distributed permanent natural ventilation, e.g. openings at each car parking level with an aggregate equivalent area equal to at least 1/20th of the floor area at that level, of which at least 25% should be on each of two opposing walls.
b. Mechanically ventilated car parks
i. either the provision of both permanent natural ventilation openings of equivalent area not less than 1/40th of the floor area and a mechanical ventilation system capable of at least three air changes per hour (ach); or
for basement car parks, the provision of a mechanical ventilation system capable of at least six air changes per hour (ach).
ii. for exits and ramps, where cars queue inside the building with engines running, provisions should be made to ensure a local ventilation rate of at least 10 air changes per hour (ach).
6.21 Further guidance can be found in Code of practice for ground floor, multi-storey and underground car parks published by the Association for Petroleum and Explosives Administration (www.apea.org.uk); CIBSE Guide B:2005, Section 184.108.40.206; and Health and Safety Publication EH40: Occupational exposure limits for limiting concentration of exhaust pollutants. Fire safety issues are considered in Approved Document B.