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F – Ventilation

Contents

Section 1: Introduction

What is an Approved Document?

This is an extract from Approved Document F. It has been edited to make it more relevant to house building.
If in doubt, view the original document on the government web site.

1.1   This document has been approved by the Secretary of State to provide practical guidance on ways of complying with the requirements in Part F of Schedule 1 to, and regulations 39, 42 and 44 (in so far as it relates to fixed systems for mechanical ventilation) of, the Building Regulations 2010 (SI 2010/2214) for England and Wales, and regulations 20(1) and 20(6) (in so far as it relates to fixed systems for mechanical ventilation) of the Building (Approved Inspectors etc) Regulations 2010 (SI 2010/2215) for England and Wales. The Building Regulations 2010 and the Building (Approved Inspectors etc) Regulations 2010 are referred to throughout the remainder of this document as ‘the Building Regulations’ and ‘the Approved Inspectors Regulations’ respectively.

1.2   The intention of issuing Approved Documents is to provide guidance about compliance with specific aspects of building regulations in some of the more common building situations. They set out what, in ordinary circumstances, may be accepted as reasonable provision for compliance with the relevant requirement(s) of building regulations to which they refer.

1.3   If guidance in an Approved Document is followed there will be a presumption of compliance with the requirement(s) covered by the guidance. However, this presumption can be overturned, so simply following guidance does not guarantee compliance; for example, if the particular case is unusual in some way, then ‘normal’ guidance may not be applicable. It is also important to note that there may well be other ways of achieving compliance with the requirements. There is therefore no obligation to adopt any particular solution contained in this Approved Document if you would prefer to meet the relevant requirement in some other way. Persons intending to carry out building work should always check with their Building Control Body, either the local authority or an approved inspector, that their proposals comply with building regulations.

1.4   It is important to note that this Approved Document, as well as containing guidance, also contains extracts from the Regulations. Such regulatory text must be complied with as stated. The guidance contained in this Approved Document relates only to the particular requirements of building regulations that the document addresses (set out in Section 2). However, building work may be subject to more than one requirement of building regulations. In such cases the work will also have to comply with any other applicable requirements of building regulations.

1.5   There are Approved Documents that give guidance on each of the Parts of Schedule 1 and on regulation 7. A full list of these is provided at the back of this document.

Consideration of technical risk

1.6   The construction of new buildings, and building work to existing buildings, must satisfy all the technical requirements set out in the Building Regulations. When considering the incorporation of ventilation measures in dwellings, attention should also be paid in particular to the need to comply with Part B (fire safety), Part C (site preparation and resistance to contaminants and moisture), Part E (resistance to the passage of sound), Part L (conservation of fuel and power), Part J (combustion appliances and fuel storage systems) and Part P (electrical safety), as well as Part F. The adoption of any particular ventilation measure should not involve unacceptable technical risk of, for instance, creating a cold bridge. Designers and builders should refer to the relevant Approved Documents and to other generally available good practice guidance to help minimise these risks.

How to use this Approved Document

1.7   This Approved Document is subdivided into eight sections as detailed below.
This introductory section sets out the general context in which the guidance in the Approved Document must be considered.

Section 2 sets out the relevant legal requirements as published in the Building Regulations.

Section 3 contains key terms and general guidance on the types of building work covered by Approved Documents, how to deal with ‘special’ areas of buildings that contain dwellings, procedures for notifying work, materials and workmanship, certification and standards, and health and safety issues.

Section 4 details the principles of ventilation and its control.

Section 5 details the guidance for ventilation of dwellings.

Section 6 details the guidance for ventilation of buildings other than dwellings.

Section 7 details the guidance for ventilation of existing buildings.

Section 8 lists standards and other publications referred to in the text.

Note. A reference to a publication is likely to be made for one of two main reasons: either the publication contains additional or more comprehensive technical detail, which it would be impractical to include in full in the Approved Document but which is needed to fully explain ways of meeting the requirements;or it is a source of more general information.The reference will be to a specified edition of the document. The Approved Document may be amended from time to time to include new references or to refer to revised editions where this aids compliance.

Where you can get further help

1.9   If you do not understand the technical guidance or other information set out in this Approved Document and the additional detailed technical references to which it directs you, there are a number of routes through which you can seek further assistance:
  • the CLG website
  • the Planning Portal website
  • if you are the person undertaking the building work you can seek assistance either from your local authority building control service or from your approved inspector (depending on which building control service you are using, or intend to use, to certify compliance of your work with the requirements of the Building Regulations);
  • businesses registered with a competent person self-certification scheme may be able to get technical advice from their scheme operator;
  • if your query is of a highly technical nature you may wish to seek the advice of a specialist, or industry technical body, in the area of concern.

Responsibility for compliance

1.10   It is important to remember that if you are the person (e.g. designer, builder, installer) carrying out building work to which any requirement of building regulations applies you have a responsibility to ensure that the work complies with any such requirement. The building owner may also have a responsibility for ensuring compliance with building regulation requirements and could be served with an enforcement notice in cases of non-compliance.
Section 2 is omitted

Section 3: General guidance

Key Terms

3.1   The following are key terms used in this document:

Air permeability is the physical property used to measure the airtightness of the building fabric. It is defined as air leakage rate per hour per square metre of envelope area at a test reference pressure differential across the building envelope of 50 Pascal (50 N/m²). The design air permeability is the target value set at the design stage.

Airtightness is a general descriptive term for the resistance of the building envelope to infiltration with ventilators closed. The greater the airtightness at a given pressure difference across the envelope, the lower the infiltration.

Automatic control is where a ventilation device is opened and closed or switched on and off or its performance is adjusted by a mechanical or electronic controller which responds to a relevant stimulus. That stimulus is usually related to the humidity of the air in a room, pollutant levels (e.g. carbon dioxide concentration in a room), occupancy of the space (e.g. using a passive infra-red motion detector) or pressure difference across the device (e.g. due to the wind outside).

Background ventilator is a small ventilation opening designed to provide controllable whole building ventilation. See Diagram 1.

Basement (in relation to dwellings) is a dwelling, or a usable part of a dwelling (i.e. a habitable room), that is situated partly or entirely below ground level. Note that a cellar is distinct from a basement in that it is used only for storage, heating plant or purposes other than habitation.

Bathroom is a room containing a bath or shower and, in addition, can also include sanitary accommodation.

BCB or Building Control Body is a local authority or an approved inspector.

Cellar is a part of a dwelling which is situated partly or entirely below ground level, and is distinct from a basement in that it is used only for storage, heating plant or purposes other than habitation.

Closable opening is a ventilation opening which may be opened and closed under either manual or automatic control.

Common space is a space where large numbers of people are expected to gather, such as a shopping mall or cinema/theatre foyer. For the purposes of this Approved Document, a space used solely or principally for circulation (e.g. a corridor or lift lobby in an office building or blocks of flats) is not a common space.

Continuous operation is where a mechanical ventilation device runs all the time, e.g. mechanical extract ventilation (MEV) and mechanical ventilation with heat recovery (MVHR). The air flow rate provided by the mechanical ventilation need not be constant but may be varied, under either manual or automatic control, in response to the demand for pollutant or water vapour removal.

Equivalent area is a measure of the aerodynamic performance of a ventilator. It is the area of a sharp-edged circular orifice which air would pass through at the same volume flow rate, under an identical applied pressure difference, as the opening under consideration.

Extract ventilation is the removal of air directly from a space or spaces to outside. Extract ventilation may be by natural means (e.g. by passive stack ventilation) or by mechanical means (e.g. by an extract fan or central system).

Free area is the geometric open area of a ventilator.

Gross internal volume is the total internal volume of the heated space, including the volume of all furniture, internal walls, internal floors, etc.

Habitable room is a room used for dwelling purposes but which is not solely a kitchen, utility room, bathroom, cellar or sanitary accommodation.

Infiltration is the uncontrolled exchange of air between inside a building and outside through cracks, porosity and other unintentional openings in a building, caused by pressure difference effects of the wind and/or stack effect.

Intermittent operation is where a mechanical ventilator does not run all the time, usually running only when there is a particular need to remove pollutants or water vapour (e.g. during cooking or bathing). Intermittent operation may be under either manual control or automatic control.

Manual control is where a ventilation device is opened and closed, or switched on and off, or its performance is adjusted by the occupants of a room or building (see automatic control).

Occupiable room is a room in a building other than a dwelling that is occupied by people, such as an office, workroom, classroom or hotel bedroom, but not a bathroom, sanitary accommodation, utility room or rooms or spaces used solely or principally for circulation, building services plant or storage purposes.

Passive stack ventilation (PSV) is a ventilation system using ducts from terminals in the ceiling of rooms to terminals on the roof that extract air to outside by a combination of the natural stack effect and the pressure effects of wind passing over the roof of the building.

Permanent opening is a ventilation opening which is permanently fixed in the open position.

Purge ventilation is manually controlled ventilation of rooms or spaces at a relatively high rate to rapidly dilute pollutants and/or water vapour. Purge ventilation may be provided by natural means (e.g. an openable window) or by mechanical means (e.g. a fan).

Purpose-provided ventilation is that part of the ventilation of a building provided by ventilation devices designed into the building (e.g. via background ventilators, PSV, extract fans, mechanical ventilation or air-conditioning systems).

Sanitary accommodation is a space containing one or more water closets or urinals. Sanitary accommodation containing one or more cubicles counts as a single space if there is free circulation of air throughout the space.

Stack effect is the pressure differential between inside and outside a building caused by differences in the density of the air due to an indoor/outdoor temperature difference.

Surface water activity is a measure of the availability of water to micro-organisms, and is determined from the ratio of the vapour pressure of the water in the substrate to that of pure water at the same temperature and pressure. This ratio is, in steady-state conditions, numerically equal to the equilibrium relative humidity of the air, except that the latter is commonly expressed as a percentage (from IEA Annex 14 source book, 1991).

Utility room is a room containing a sink or other feature or equipment which may reasonably be expected to produce water vapour in significant quantities.

Ventilation is the supply and removal of air (by natural and/or mechanical means) to and from a space or spaces in a building. It normally comprises a combination of purpose-provided ventilation and infiltration.

Ventilation opening is any means of purpose provided ventilation (whether it is permanent or closable) which opens directly to external air, such as the openable parts of a window, a louvre or a background ventilator. It also includes any door which opens directly to external air.

Wet room is a room used for domestic activities (such as cooking, clothes washing and bathing) which give rise to significant production of airborne moisture, e.g. a kitchen, utility room or bathroom. For the purposes of Part F, sanitary accommodation is also regarded as a wet room.

Whole building ventilation (general ventilation) is nominally continuous ventilation of rooms or spaces at a relatively low rate to dilute and remove pollutants and water vapour not removed by operation of extract ventilation, purge ventilation or infiltration, as well as supplying outdoor air into the building. For an individual dwelling this is referred to as ‘whole dwelling ventilation’.

Types of work covered by this Approved Document

3.2    This Approved Document gives guidance on what, in ordinary circumstances, may be considered reasonable provision for compliance with the requirements of Part F of Schedule 1 to, and regulations 39, 42 and 44 (in so far as it relates to fixed systems for mechanical ventilation) of, the Building Regulations, and regulations 20(1) and 20(6) (in so far as it relates to fixed systems for mechanical ventilation) of the Approved Inspectors Regulations, for those erecting new dwellings and buildings other than dwellings, or carrying out work on existing buildings.

Exemptions

3.3   The erection or extension of a number of classes of buildings is exempt under regulation 9 of, and Schedule 2 to, the Building Regulations from the requirements to comply with the requirements in paragraph 3.2 above:
  1. buildings controlled under the Manufacture and Storage of Explosives Regulations 2005, the Nuclear Installations Act 1965 or included in the schedule of  monuments maintained under section 1 of the Ancient Monuments and Archaeological Areas Act 1979;
  2. detached buildings into which people do not normally go, or go only intermittently for the purpose of inspecting or maintaining fixed plant or machinery, provided that the buildings are a specified distance from buildings into which people normally go;
  3. greenhouses providing that the principal purpose of the building is not retailing, packing or exhibiting;
  4. agricultural buildings (as defined), provided that no part of the building is used as a dwelling, that the building is at least one and one-half times its height from a building containing sleeping accommodation, and that there is a fire exit not more than 30 metres distant from any point in the building. Agricultural buildings used principally for retailing, packing or exhibiting fall outside the exemption;
  5. temporary buildings not intended to remain in place for more than 28 days;
  6. ancillary buildings used for the disposal of buildings or building plots on site; buildings on the site of construction or civil engineering works for use only during the course of those works and containing no sleeping accommodation; and buildings on the site of mines and quarries which do not contain dwellings, nor are used as offices or showrooms;
  7. detached single-storey buildings, with less than 30 m2 floor area and containing no sleeping accommodation, which are either constructed substantially of non-combustible material or at least 1 metre from the boundary of their curtilage;
  8. detached buildings of less than 30 m2 floor area, designed and intended to be used as shelters from nuclear, chemical or conventional weapons and used for no other purpose, provided the excavation for the building is at least 1 metre plus the depth of excavation from any other exposed structure;
  9. detached buildings of less than 15 m2 floor area containing no sleeping accommodation; and
  10. extensions of buildings at ground level with a floor area less than 30 m2 by the addition of a conservatory, porch, covered yard, covered way, or carport open on at least two sides.

Notification of work covered by the ventilation requirements

3.4   In most cases where it is proposed to carry out notifiable ventilation work on a building it will be necessary to notify the work to a BCB in advance. This notification would usually be by way of a full plans application or a building notice given to a local authority, or an initial notice given jointly with the approved inspector. However, there are three circumstances where such work need not be notified to a BCB in advance:

Competent person self-certification schemes

3.5   It is not necessary to notify a BCB in advance of work which is to be carried out by a person registered with a competent person self-certification scheme for that type of work. In order to join such a scheme a person must demonstrate competence to carry out the type of work the scheme covers, and also the ability to comply with all relevant requirements in the Building Regulations.

3.6   Where work is carried out by a person registered with a competent person scheme, regulation 20 of the Building Regulations and regulation 20(1) of the Approved Inspectors Regulations require that the occupier of the building be given, within 30 days of the completion of the work, a certificate confirming that the work complies fully with all applicable building regulation requirements. There is also a requirement that the BCB be given a notice of the work carried out, again within 30 days of the completion of the work. These certificates and notices are usually made available through the scheme operator.

3.7   BCBs are authorised to accept these certificates and notices as evidence of compliance with the requirements of the Building Regulations. Local authority inspection and enforcement powers remain unaffected, but they are normally used only in response to a complaint that work does not comply.

3.8   There are a number of competent person schemes for the installation of mechanical ventilation and air-conditioning systems in buildings. A list of the schemes and the types of work for which they are authorised is available at www.communities.gov.uk.
Emergency repairs

3.9   Where the work involves an emergency repair, e.g. to a failed fan, in accordance with regulation 12(8) of the Building Regulations there is no need to delay making the repair in order to make an advance notification to the BCB where this is not practicable. However, in such cases it will still be necessary for the work to comply with the relevant requirements and to give a notice to the BCB at the earliest opportunity, unless an installer registered under an appropriate competent person scheme carries out the work. A completion certificate can then be issued in the normal way.

Minor works
3.10   Where the work is of a minor nature as described in the schedule of non-notifiable work (Schedule 4 to the Building Regulations), the work must still comply with the relevant requirements but need not be notified to the BCB. In relation to mechanical ventilation and air-conditioning systems such work includes:
  • replacement of parts, or the addition of an output or control device where testing and adjusting is not possible or would not affect the system’s energy efficiency;
  • provision of a self-contained mechanical ventilation or air-conditioning appliance provided that any electrical work is exempt from a requirement to give advance notice to a BCB, and testing and adjustment is not possible or would not affect its energy efficiency, and the appliance is not installed in a room containing an open-flued combustion appliance. Examples might be a cooker hood, a bathroom extract fan or a room air-conditioning unit, which cannot be adjusted from their factory settings.

Historic and traditional buildings

SPAB may be useful for guidance on dealing with historic buildings

3.11   As mentioned above in paragraph 3.3a, buildings included in the schedule of monuments maintained under section 1 of the Ancient Monuments and Archaeological Areas Act 1979 are exempt from compliance with the requirements of the Building Regulations. There are other classes of buildings where special considerations may apply in deciding what is adequate provision for ventilation:

  1. listed buildings;
  2. buildings in conservation areas;
  3. buildings which are of architectural and historical interest and which are referred to as a material consideration in a local authority’s development plan or local development framework;
  4. buildings which are of architectural and historical interest within national parks, areas of outstanding natural beauty, registered historic parks and gardens, registered battlefields, the curtilages of scheduled ancient monuments, and world heritage sites; and
  5. buildings of traditional construction with permeable fabric that both absorbs and readily allows the evaporation of moisture.

3.12   When undertaking work on or in connection with a building that falls within one of the classes listed above, the aim should be to provide adequate ventilation as far as is reasonable and practically possible. The work should not prejudice the character of the host building or increase the risk of long-term deterioration of the building fabric or fittings.

3.13   The guidance given by English Heritage and in BS 7913 Principles of the conservation of historic buildings should be taken into account in determining appropriate ventilation strategies for building work in historic buildings.

3.14   In general, new extensions to historic or traditional dwellings should comply with the standards of ventilation as set out in this Approved Document. The only exception would be where there is a particular need to match the external appearance or character of the extension to that of the host building.

3.15   Particular issues relating to work in historic buildings that warrant sympathetic treatment and where advice from others could therefore be beneficial include:
  1. restoring the historic character of a building that has been subject to previous inappropriate alteration, e.g. replacement windows, doors and rooflights;
  2. rebuilding a former historic building (e.g. following a fire or filling a gap site in a terrace);
  3. making provision for the fabric of historic buildings to ‘breathe’ to control moisture and potential long-term decay problems.

3.16   In determining what is adequate ventilation in the circumstances, it is important that the BCB takes into account the advice of the local authority’s conservation officer. The views of the conservation officer are particularly important where building work requires planning permission and/or listed building consent.

Material change of use

More information on change of use here

3.17   A change of use occurs when there is a change in the purposes for which, or circumstances in which, an existing building or part of a building is used. For the purposes of building regulations, a material change of use occurs where, after the change:

  1. the building or part of a building is used as a dwelling, where previously it was not;
  2. the building or part of a building contains a flat, where previously it did not;
  3. the building or part of a building is used as a hotel or a boarding house, where previously it was not;
  4. the building or part of a building is used as an institution, where previously it was not;
  5. the building or part of a building is used as a public building, where previously it was not;
  6. the building or part of a building is not a building described in Classes 1 to 4 in Schedule 2, where previously it was;
  7. the building or part of a building, which contains at least one dwelling, contains a greater or lesser number of dwellings than it did previously;
  8. the building or part of a building contains a room for residential purposes, where previously it did not;
  9. the building or part of a building, which contains at least one room for residential purposes, contains a greater or lesser number of such rooms than it did previously;or
  10. the building or part of a building is used as a shop, where previously it was not.
3.18   Where a building undergoes any of the material changes of use described above it will be necessary for the resultant building to comply with the requirements of Part F of the Building Regulations. Where only part of the building undergoes a material change of use, normally only that part needs to comply with the requirements of Part F.

Live-work units

3.19   If a unit contains both living accommodation and space to be used for commercial purposes (e.g. workshop or office), the whole unit should be treated as a dwelling for the purposes of this Approved Document as long as the commercial part could revert to domestic use. This could be the case if, for example:
  1. there is direct access between the commercial space and the living accommodation; and
  2. both are contained within the same thermal envelope; and
  3. the living accommodation occupies a substantial proportion of the total area of the unit.

Sub-paragraph c means that the presence of (e.g.) a small manager’s flat in a large non-domestic building would not result in the whole building being treated as a dwelling. Similarly, the existence of a room used as an office or utility space within a dwelling would not mean that the building should not be treated as a dwelling.

Mixed use developments

3.20   When constructing a dwelling as part of a larger building that contains other types of accommodation, sometimes called a mixed use development, Section 5 of this Approved Document should be used for guidance in relation to each individual dwelling. Section 6 gives guidance relating to the non-dwelling parts of such buildings.

Materials and workmanship

3.21   Any building work which is subject to the requirements imposed by Schedule 1 to the Building Regulations shall be carried out in accordance with regulation 7. Guidance on meeting these requirements on materials and workmanship is contained in Approved Document 7.

3.22   Building Regulations are made for specific purposes, primarily the health and safety, welfare and convenience of people and for energy conservation. Standards and other technical specifications may provide relevant guidance to the extent that they relate to these considerations. However, they may also address other aspects of performance or matters which, although they relate to health and safety etc., are not covered by the Building Regulations.

3.23   When an Approved Document makes reference to a named standard, the relevant version of the standard to which it refers is the one listed at the end of the publication. However, if this version has been revised or updated by the issuing standards body, the new version may be used as a source of guidance provided it continues to address the relevant requirements of the Regulations.

The Workplace (Health, Safety and Welfare) Regulations 1992

3.24   The Workplace (Health, Safety and Welfare) Regulations 1992, as amended, apply to the common parts of flats and similar buildings if people such as cleaners, wardens and caretakers are employed to work in these common parts. These Regulations contain some requirements which affect building design. The main requirements are now covered by the Building Regulations, but for further information see Workplace health, safety and welfare, Workplace (Health, Safety and Welfare) Regulations 1992, Approved Code of Practice and guidance , HSE publication L24, 1996.

3.25   Where the requirements of the Building Regulations that are covered by this Approved Document do not apply to dwellings, the provisions may still be required in the situations described above in order to satisfy the Workplace Regulations.

Section 4: Introduction to the provisions

Performance

4.1   The purpose of this section is to outline briefly what ventilation in buildings is for and the philosophy behind the guidance for ventilation given in Approved Document F. More detail is given in some of the informative Appendices at the end of this Approved Document.

4.2   The key aim of the requirement of Part F1(1) is that a ventilation system is provided that, under normal conditions, is capable of limiting the accumulation of moisture, which could lead to mould growth, and pollutants originating within a building which would otherwise become a hazard to the health of the people in the building.

4.3   In general terms, the requirement may be achieved by providing a ventilation system which:
  1. extracts, before it is generally widespread, water vapour from areas where it is produced in significant quantities (e.g. kitchens, utility rooms and bathrooms);
  2. extracts, before they are generally widespread, pollutants which are a hazard to health from areas where they are produced in significant quantities (e.g. rooms containing processes or activities which generate harmful contaminants);
  3. rapidly dilutes, when necessary, pollutants and water vapour produced in habitable rooms, occupiable rooms and sanitary accommodation;
  4. makes available over long periods a minimum supply of outdoor air for occupants and disperses, where necessary, residual pollutants and water vapour. Such ventilation should minimise draughts and, where necessary, should be reasonably secure and provide protection against rain penetration;
  5. is designed, installed and commissioned to perform in a way which is not detrimental to the health of the people in the building; and
  6. is installed to facilitate maintenance where necessary.

4.4   The guidance in this Approved Document has not been formulated to deal with the products of tobacco smoking.

4.5   Ventilation systems in buildings result in energy being used to heat fresh air taken in from outside and, in mechanical ventilation systems, to move air into, out of and/or around the building. Energy efficiency is dealt with under Part L of Schedule 1 and Regulation 40 of the Building Regulations but consideration should be given to mitigation of ventilation energy use, where applicable, by employing heat recovery devices, efficient types of fan motor and/or energy-saving control devices in the ventilation system.

The purpose of ventilation

4.6   Ventilation is simply the removal of ‘stale’ indoor air from a building and its replacement with ‘fresh’ outside air. It is assumed within the Approved Document that the outside air is of reasonable quality.

4.7   Ventilation is required for one or more of the following purposes:
  1. provision of outside air for breathing;
  2. dilution and removal of airborne pollutants, including odours;
  3. control of excess humidity (arising from water vapour in the indoor air);
  4. provision of air for fuel-burning appliances (which is covered under Part J of the Building Regulations).

4.8   Ventilation may also provide a means to control thermal comfort but this is not controlled under the Building Regulations. Part L addresses minimising energy use due to the effects of solar gain in summer.

4.9   The airborne pollutants and water vapour mentioned in paragraph 4.7b and c above include those that are released from materials and products paragraph used in the construction, decoration and furnishing of a building, and as a result of the activities of the building’s occupants.

4.10   The pollutant(s) of most importance will vary between building types (e.g. dwelling, office, factory), building uses (e.g. industrial process, shop, commercial kitchen), and even from room to room within a building (e.g. kitchen, shower room, conference room, photocopier room). Common pollutants in a dwelling are moisture and combustion products from unflued appliances (e.g. gas, oil or solid fuel cookers) and chemical emissions from construction and consumer products. Note that the ventilation system capacity, if used appropriately, is usually sufficient to remove odours arising from normal occupant activities within a dwelling. In an office building, body odour is often the key pollutant, but there are a number of other pollutant sources including the building itself, furnishings, printers and photocopiers.

Types of ventilation

4.11   Buildings are ventilated through a combination of infiltration and purpose-provided ventilation:
  • Infiltration is the uncontrollable air exchange between the inside and outside of a building through a wide range of air leakage paths in the building structure.
  • Purpose-provided ventilation is the controllable air exchange between the inside and outside of a building by means of a range of natural and/or mechanical devices.

4.12   It is important to minimise the uncontrollable infiltration and supply sufficient purpose-provided ventilation. Air tightness measures to limit infiltration are covered in Part L of the Building Regulations and its supporting Approved Documents. Approved Document F recommends methods of achieving sufficient purpose-provided ventilation, allowing for a reasonably high level of airtightness.

4.13   For the purposes of Part F, a reasonably high level of airtightness means a level which is significantly tighter than the minimum target value recommended under Part L, because all new buildings are expected to better the target value to some degree. Through good design and execution, domestic and non-domestic buildings can currently achieve an air permeability down to around 2 to 4 m3/(h.m2) of envelope area at 50 Pascal (Pa) pressure difference. Some buildings constructed are tighter than this. It can be anticipated that there will be a continual trend towards more airtight buildings due to drivers for higher energy efficiency and lower carbon emissions.

4.14   The ventilation provisions recommended for new dwellings in this Approved Document have been specified for two standard designs of air permeability:
  • In the default option, the guidance assumes zero air permeability and thus no infiltration. The building ventilation is reliant entirely on installed purpose-provided ventilation, thus ensuring sufficient ventilation for dwellings of all levels of air permeability. This option should be particularly suitable when intending to construct a more airtight dwelling, or where the person carrying out the building work does not have previous experience of closely matching design with as-constructed air permeability and may, as a consequence, achieve a significantly better performance than designed.
  • In the alternative option, the guidance assumes an infiltration of 0.15 air changes per hour (ach). The recommended purpose-provided ventilation is less as infiltration contributes to the total amount of ventilation. This option is most appropriate when designing to an air permeability leakier than 5 m3/(h.m2) at 50 Pa, and it is expected from experience that the measured air permeability will be close to the design value and will not be better than 3 m3/(h.m2) at 50 Pa.
    Paragraphs 5.8 to 5.10 provide further information.

The ventilation strategy adopted in Approved Document F

4.15   Approved Document F adopts the following strategy. (Systems which comply with the strategy are described in Sections 5 and 6.)
  • Extract ventilation from rooms where most water vapour and/or pollutants are released, e.g. due to activities such as cooking, bathing or photocopying. This is to minimise their spread to the rest of the building. This extract may be either intermittent or continuous.
  • Whole building/dwelling ventilation to provide fresh air to the building and to dilute and disperse residual water vapour and pollutants not dealt with by extract ventilation as well as removing water vapour and other pollutants which are released throughout the building (e.g. by building materials, furnishings, activities and the presence of occupants). Whole building/dwelling ventilation provides nominally continuous air exchange. The ventilation rate may be reduced or ceased when the building is not occupied. It may be necessary to purge the air when the building is re-occupied.
  • Purge ventilation throughout the building to aid removal of high concentrations of pollutants and water vapour released from occasional activities such as painting and decorating or accidental releases such as smoke from burnt food or spillage of water. Purge ventilation is intermittent, i.e. required only when such occasional activities occur. Purge ventilation provisions may also be used to improve thermal comfort, although this is not controlled under the Building Regulations.

4.16   This ventilation strategy can be delivered by a natural ventilation system or a mechanical ventilation system or a combination of both (i.e. ‘mixed-mode’ or ‘hybrid’ ventilation system). For mainly naturally ventilated buildings, it is common to use a combination of ventilators to achieve this strategy (e.g. for dwellings it is common to use intermittent extract fans for extract ventilation, trickle ventilators for whole dwelling ventilation and windows for purge ventilation). For mechanically ventilated or air-conditioned buildings, it is common for the same ventilators to provide both local extract and whole building / dwelling ventilation and, for buildings other than dwellings, to provide purge ventilation as well.

4.17   The ventilation systems and devices mentioned in this document are examples of those commonly in use at the time of writing. Other ventilation systems and devices, perhaps following a different strategy (e.g. positive input ventilation or supply air windows), may provide acceptable solutions, provided it can be demonstrated to the BCB (e.g. by use of a product or system covered by a national or European certificate issued by a European Technical Approval issuing body, provided the conditions of use are in accordance with the terms of the certificate) that they meet Requirement F1. The assessment of the suitability of a ventilation system should take account of the design air permeability of the building, and the fact that the completed building may be ‘tighter’ than the design value because of variability in construction quality.

Control of ventilation

4.18   It is important that ventilation is controllable so that it can maintain reasonable indoor air quality and avoid waste of energy. These controls can be either manual (i.e. operated by the occupant) or automatic. Demand-controlled ventilation systems employ sensors to detect the level of occupancy, water vapour or other pollutants and adjust the ventilation rate accordingly in order to avoid over-ventilation and so reduce energy consumption.

4.19   Manually controlled trickle ventilators (the most common type of background ventilators) can be located over the window frames, in window frames, just above the glass or directly through the wall (see Diagram 1 in Key terms). They are positioned typically 1.7 m above floor level to avoid discomfort due to cold draughts. These ventilators often incorporate a simple flap that allows users to shut off the ventilation – depending on external weather conditions. Trickle ventilators are intended to be normally left open in occupied rooms in dwellings. A window with a night latch position is not recommended because of the difficulty of measuring the equivalent area, the greater likelihood of draughts and the potential increased security risk in some locations.

4.20   In dwellings, humidity-controlled devices are available to regulate the humidity of the indoor air and, hence, minimise the risk of condensation and mould growth. These are best installed as part of an extract ventilator in moisture-generating rooms (e.g. kitchen or bathroom). Humidity control is not appropriate for sanitary accommodation, where the dominant pollutant is normally odour. Trickle ventilators are available which ‘throttle down’ the ventilation flow passage(s) according to the pressure difference across the ventilator to reduce draught risks during windy weather. Manufacturers should be consulted when selecting the correct type of pressure-controlled trickle ventilator.

4.21   Other types of automatic control may be suitable for regulating ventilation devices (e.g. trickle ventilators, ventilation fans, dampers and air terminal devices) in dwellings. In such cases, it is important that the device controls the ventilation air supply and/or extract according to the need for ventilation in the space to remove or dilute indoor pollutants and water vapour. Trickle ventilators with automatic controls should also have manual override, so that the occupant can close the ventilator to avoid draughts and fully open the ventilator to provide maximum air flow when required. For pressure-controlled trickle ventilators that are fully open at typical conditions (e.g. 1 Pa pressure difference), only a manual close option is recommended.

4.22   In buildings other than dwellings, more sophisticated automatic control systems are available. These may be based on sensors located within the building, e.g. occupancy sensors (using local passive infra-red detectors) or indoor carbon dioxide concentration sensors (using electronic carbon dioxide detectors) as an indicator of occupancy level and, therefore, body odour.

Performance-based guidance

4.23  This Approved Document focuses on performance-based guidance which suggests to the designer what level of ventilation should be sufficient, rather than how it should be achieved. Therefore, the designer has the freedom to use whatever ventilation provisions suit a particular building, including the use of innovative products and solutions, if it can be demonstrated that they meet the performance standard recommended in this Approved Document.

4.24   The actual performance criteria for acceptable levels of moisture and pollutants are given in Appendix A. The air flow rates necessary to meet the performance criteria are given in the main guidance.

4.25   Simple guidance in the form of ventilator sizes for the whole dwelling is also provided to make it easier for designers to meet building regulations requirements in common situations.

Equivalent area of ventilators

4.26   Equivalent area is used in the Approved Document instead of free area for the sizing of background ventilators (including trickle ventilators) because it is a better measure of the air flow performance of a ventilator. Unlike equivalent area, free area is simply the physical size of the aperture of the ventilator but may not accurately reflect the air flow performance which the ventilator will achieve. The more complicated and/or contorted the air flow passages in a ventilator, the less air will flow through it. So, two different ventilators with the same free area will not necessarily have the same air flow performance. A European Standard, BS EN 13141-1:2004 (Clause 4), includes a method of measuring the equivalent area of background ventilator openings.

4.27   As equivalent area cannot be verified with a ruler, it will be difficult to demonstrate to Building Control Bodies that trickle ventilators and similar products have the correct equivalent area unless it is clearly marked on the product. For this reason, it is preferable to use ventilators which have the equivalent area (in mm² at 1 Pa pressure difference), or equivalent area per metre (where the equivalent area of the product varies according to length) marked on the product in an easily visible location from the inside of the dwelling when installed. Where it is not practical for the manufacturer to mark the ventilator because it can be used in conjunction with a range of other components, some form of temporary marking for the installed system should be acceptable to the BCB.

Ventilation effectiveness

4.28   Ventilation effectiveness is a measure of how well a ventilation system works in terms of delivering the supply air to the occupants of a building. If the supply air is mixed fully with the room air before it is breathed by the occupants, the ventilation effectiveness is 1. If the supply air is extracted from the room before it mixes with any room air, the ventilation effectiveness is 0. If the supply air reaches the occupant without mixing with any room air, the ventilation effectiveness tends towards infinity.

4.29   This is important as a system with a higher ventilation effectiveness achieves acceptable pollutant levels at the occupant’s breathing zone for a lower air supply rate, and offers potentially significant energy savings. However, it has been decided not to make an allowance for any reduction of fresh air supply rates based on ventilation effectiveness in Approved Document F at this time. This is because ventilation effectiveness is dependent on the ventilation system design, its installation and the way in which occupants use the space. While it is possible to predict what the ventilation effectiveness of a system should be, there is currently insufficient knowledge of the actual ventilation effectiveness achieved in buildings to allow designers to guarantee performance and so avoid significant under-ventilation by reducing air supply rates. This is because ventilation effectiveness may be influenced by factors beyond the designer’s control such as occupant usage (e.g. seating plan and use of computers within a space and whether the space is being heated or cooled by the ventilation air). In the designs shown in this Approved Document, it has been assumed that the ventilation effectiveness is 1.0. CIBSE Guide A provides further information on ventilation effectiveness.

Source control

4.30   A complementary strategy for achieving good indoor air quality is to reduce the release of water vapour and/or air pollutants into the indoor air, i.e. source control. Source control is not considered within the main guidance of the Approved Document owing to limited knowledge about the emission of pollutants from construction and consumer products used in buildings and the lack of suitable labelling schemes for England and Wales. Some construction products such as glass, stone and ceramics are by their nature low emitters of air pollutants. Currently, some paints are labelled for their volatile organic compound (VOC) content, and some wood-based boards (class E1, BS EN 13986:2004) are available with low formaldehyde emission. This allows suitable products to be chosen when good indoor air quality is a priority, but at the present time it is not practical to make an allowance for use of these products in the ventilation requirements. Further information about control of emissions from construction products is available in BRE Digest 464.

4.31  Exposure to house dust mite (HDM) allergens can lead to allergic sensitisation and to exacerbation of allergic conditions. The moisture criteria needed to avoid HDM are more complex and demanding than those needed to avoid mould. The reduction of mite growth may be feasible in UK dwellings via appropriate ventilation, heating and moisture control as part of an integrated approach that involves the removal of existing mite allergens.

4.32   Useful information may be found in the World Health Organisation (WHO) publication, House dust mites, Crowther D and Wilkinson T (2008), which is included in Public health significance of urban pests, Bonnefoy X, Kampen H and Sweeney K, WHO Regional Office for Europe

4.33   Further information and suggested measures for source control are given in Review of health and safety risk drivers (BD 2518) (Now archived)

Noise

4.34   The noise caused by ventilation systems is not controlled under the Building Regulations. However, such noise may be disturbing to the occupants of a building and it is recommended that measures be taken to minimise noise disturbance. For example, in noisy areas, in order to reduce noise entering the building through the ventilation system, it may be appropriate to use sound-attenuating ventilation products depending on the noise level and any planning conditions.

4.35    Noise from the ventilation system may also disturb people who are outside the building, so measures to minimise externally emitted noise should also be considered.

4.36   Noise generated by ventilation fans (which may travel through ducts) and noise from the fan unit may disturb the occupants of the building and so discourage their use. Therefore, the designer should consider minimising noise by careful design and the specification of quieter products.

To ensure good acoustic conditions, the average A-weighted sound pressure level in noise sensitive rooms, such as bedrooms and living rooms, should not exceed 30 dB LAeq,T (see Note below). In less sensitive rooms, such as kitchens and bathrooms, a higher level would be acceptable, e.g. 35 dB LAeq,T .Noise from a continuously running mechanical ventilation system on its  minimum low rate should not normally exceed these levels, and should preferably be lower in order to minimise the impact of the ventilation system.

The main issues to be addressed in minimising the noise impact of the ventilation system are the noise from the fan unit entering the ducts, and the attenuation provided by the ducts, bends and junctions and the characteristics of the room grill. The noise breaking out of the fan unit casing may also be significant in adjacent rooms. The characteristics of the room will also affect the noise level.

Methods for measuring the sound power level produced by the fan unit of decentralised extract, centralised extract, and balanced supply and extract with heat recovery systems are under development. When available, they should be read in conjunction with the appropriate parts of BS EN 13141.

Note:
The noise index LAeq,T  is used in BS 8233:1999, where T is the duration of the measurement. If the noise from the sound source is steady (e.g. fluctuating by up to 3 dB) a measuring time of 1 minute will be adequate and the LAeq,1 min level will be similar to the dB(A) level used elsewhere. If the noise from the sound source fluctuates more than this a longer measuring time (T) will be required.

Fire precautions

4.37   Where ducting passes through a fire-resisting wall/floor or fire compartment, the required measures to ensure compliance with Part B of the Building Regulations must be taken.

Modular and portable buildings

4.38   Buildings constructed from sub-assemblies that are delivered newly made or selected from stock should be treated no differently from any other new building and must comply with all the relevant requirements in Schedule 1 to the Building Regulations 2010 that were in force when they were manufactured. For guidance on energy efficiency requirements, see Approved Document L2A.

Installation of ventilation systems

4.39   It is recommended that ventilation systems are installed in new and existing dwellings in accordance with the guidance in the 2010 edition of the Domestic ventilation compliance guide. The guide is referenced at relevant points of this Approved Document – in Section 5, New dwellings, and in Section 7, Work on existing buildings.

4.40   Section 5 of the Domestic ventilation compliance guide includes an installation checklist which should be completed by the system installer. It also includes an installation inspection sheet where the equivalent area of background ventilators should be recorded.

4.41   Installation guidance for buildings other than dwellings can be found in the references listed in Table 6.3.

Air flow rate testing and commissioning of ventilation systems

4.42   The Regulations require:

  • mechanical ventilation systems to be commissioned (where they can be tested and adjusted) to provide adequate ventilation and a commissioning notice to be given to the BCB;
  • air flow rates for mechanical ventilation systems in new dwellings to be measured and a notice to be given to the BCB.
4.43   For dwellings, the procedures approved by the Secretary of State for measurement of air flow rates and for commissioning of mechanical ventilation systems are in Sections 2 and 3 of the Domestic ventilation compliance guide. Section 5 of the guide contains air flow measurement test and commissioning sheets which should be completed by the person responsible for commissioning.

4.44   For commissioning of non-domestic ventilation systems, the commissioning procedure approved by the Secretary of State is CIBSE Code M, available from www.cibse.org.

4.45   The commissioning of mechanical ventilation systems to provide adequate ventilation under Part F of the Building Regulations will need to be carried out with the commissioning of such systems to ensure that they use no more fuel and power than is reasonable in the circumstances under Part L of the Building Regulations. It is permissible for the notice of  commissioning to be given to the BCB to cover the commissioning required under both Parts F and L. Approved Documents L1A, L1B, L2A and L2B give guidance on commissioning required by Part L.

4.46   In addition, guidance on commissioning ventilation ductwork is provided in the HVCA guidance documents DW/144 Specification for sheet metal ductwork: low, medium and high pressure/velocity air systems, DW/154  Specification for plastics ductwork, and DW/143 Practical guide to ductwork leakage testing, all available from www.hvca.org.uk. (Now archived)

Provision of information

4.47   The Regulations require sufficient information about the ventilation system and its maintenance requirements to be given to owners so that the ventilation system can be operated to provide adequate air flow.

4.48   For new and existing dwellings, Section 4 of the Domestic ventilation compliance guide lists the documents that it is recommended should be given to the dwelling owner at installation handover. The inspection checklist and air flow measurement test and commissioning sheet in Section 5 should form part of the information pack. The parts of Section 5 covering air flow measurement and commissioning should also be given to the BCB.

4.49   For new and existing buildings other than dwellings, a way of showing compliance would be to follow the guidance in Approved Documents L2A and L2B, which reference the CIBSE TM 31 Building log book toolkit, 2006.

Section 5: New dwellings

Introduction to provisions

5.1   This Approved Document shows three main ways of complying with the ventilation requirements of the Building Regulations:
  1. providing the ventilation rates set out in paragraphs 5.4 to 5.7; or
  2. following the system guidance set out:
    for dwellings without basements in paragraphs 5.8 to 5.10. This guidance covers all levels of design air permeability. Alternative guidance is also provided for dwellings designed to an air permeability leakier than (>) 5 m3/(h.m2) at 50 Pa where the developer from experience will not construct significantly more airtight dwellings (not better than 3 m3/(h.m2) at 50 Pa);or
    for dwellings with basements in paragraphs 5.11 to 5.13; or
  3. 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.
5.2   There should be reasonable access for maintenance. This should include access for the purpose of changing filters, replacing defective components and cleaning ductwork.

5.3   Note that extract fans lower the pressure in a building, which can cause the spillage of combustion products from open-flued appliances (i.e. the combustion gases may fill the room instead of going up the flue or chimney). This can occur even if the appliance and the fan are in different rooms. Ceiling sweep fans produce air currents and hence local depressurisation, which can also cause the spillage of flue gases from open-flued gas appliances or from solid fuel open fires. In buildings where it is intended to install open-flued combustion appliances and extract fans, the combustion appliance should be able to operate safely whether or not the fans are running. A way of showing compliance in these circumstances would be to follow the guidance given in Approved Document J on both the installation of the appliances and tests to show that combustion appliances operate safely whether or not fans are running.

Ventilation rates

5.4   The performance will be achieved by providing the air flow rates set out in paragraphs 5.5 to 5.7. The air flow rates specified are for the performance of the complete installation. The performance of the ventilation devices (and associated components such as ducting for fans) should be tested according to the Standards listed under ‘Performance test methods’ in Table 5.3. All natural and mechanical systems should be fully commissioned, and guidance is given in the Domestic ventilation compliance guide, available from: www.planningportal.gov.uk/approveddocuments.

5.5   Extract ventilation to outside is required in each kitchen, utility room and bathroom and for sanitary accommodation. The extract can be either intermittent or continuously operating. The intermittent rate, and for continuous systems the minimum extract air flow rates at the highest and lowest settings, should be no less than specified in Table 5.1a.

5.6   The whole dwelling ventilation rate for the supply of air to the habitable rooms in a dwelling should be no less than specified in Table 5.1b.

5.7   Purge ventilation provision is required in each habitable room and should be capable of extracting a minimum of four air changes per hour (ach) per room directly to outside. Normally, openable windows or doors can provide this function (see Appendix B), otherwise a mechanical extract system should be provided. In other rooms (e.g. kitchens and bathrooms) the mechanical or passive stack extract provisions should be sufficient, although passive stack ventilation will take longer to purge the room.

Ventilation systems for dwellings without basements

5.8   The performance required for dwellings without basements could be achieved by following Steps 1 and 2 below. Worked examples for each system are given in Appendix C.

5.9   For each system, guidance is given for dwellings to cover all design air permeabilities. This guidance is therefore suitable for all dwellings and, for ventilation purposes, it is not necessary for the as-built permeability to be close to the design permeability.

5.10   In addition to this guidance, for each system alternative guidance is provided for dwellings with as-built air permeabilities leakier than (>) 3 m3/(h.m2) at 50 Pa. It is recommended that this option is selected only if designing to an air permeability leakier than (>) 5 m3/(h.m2) at 50 Pa and if the person carrying out the building work has previous experience of closely matching design with as-built air permeability levels. If the alternative guidance is followed, and it is subsequently found that either
  • the tested air permeability for that dwelling is tighter than or equal to (≤) 3 m3/(h.m2) at 50 Pa, or
  • if the dwelling is not tested, but another dwelling of the same dwelling type tested under regulation 43 is tighter than or equal to (≤) 3 m3/(h.m2) at 50 Pa,

it may be necessary for the BCB to ask for more air permeability testing to be carried out to ensure all dwellings in the sample are provided with adequate ventilation.

Step 1: Select one of the following four ventilation systems (illustrated in Diagram 2a).

System 1: Background ventilators and intermittent extract fans. Guidance on minimum provisions for extract and whole dwelling ventilation is set out in Table 5.2a. Note that it includes separate guidance for dwellings with habitable rooms having only a single exposed façade.

System 2: Passive stack ventilation (PSV). Guidance on minimum provisions for extract and whole dwelling ventilation is set out in Table 5.2b.

System 3: Continuous mechanical extract (MEV). Guidance on minimum provisions for extract and whole dwelling ventilation is set out in Table 5.2c.

System 4: Continuous mechanical supply and extract with heat recovery (MVHR). Guidance on minimum provisions for extract and whole dwelling ventilation is set out in Table 5.2d.

Step 2: See Table 5.3 for guidance on performance test methods for the products chosen.

 

 

Ventilation systems for basements

5.11   For a dwelling which includes a basement that is connected to the rest of the dwelling above ground by a large permanent opening (e.g. an open stairway), the whole dwelling including the basement should be ventilated in accordance with paragraph 5.8 (for dwellings without basements) and treated as a multi-storey dwelling. If the basement has only a single exposed façade, while the rest of the dwelling above ground has more than one exposed façade, ventilation systems 3 and 4 are preferred, following the guidance in paragraph 5.8. If systems 1 or 2 are to be used, seek expert advice.

5.12   For a dwelling which includes a basement that is not connected to the rest of the dwelling above ground by a large permanent opening:
  1. the part of the dwelling above ground should be considered separately and ventilated in accordance with paragraph 5.8. If the part of the dwelling above ground has no bedrooms, assume it has one bedroom for the purpose of determining ventilation provisions; and
  2. the basement should be treated separately as a single-storey dwelling above ground level in accordance with paragraph 5.8. If the basement has no bedrooms, assume it has one bedroom for the purpose of determining ventilation provisions. The  guidance on natural ventilation given in the Approved Document may not be appropriate for this situation and expert advice should be sought.
5.13   A dwelling which comprises only a basement should be treated as a single-storey dwelling above ground level in accordance with paragraph 5.8. The guidance on natural ventilation given in the Approved Document may not be appropriate for this situation and expert advice should be sought.

Ventilation of a habitable room through another room or a conservatory

5.14   In a habitable room not containing openable windows (i.e. an internal room) the requirement will be met if the room is ventilated either through another habitable room (see paragraph 5.15) or through a conservatory (see paragraph 5.16).

5.15   A habitable room not containing openable windows may be ventilated through another habitable room (see Diagram 3) if:
  1. there is, from the habitable rooms to outside, provision for both: i.   purge ventilation, one or more ventilation openings, with a total area given in Diagram 3 based on at least the combined floor area of the habitable rooms; and ii.  background ventilation of at least 8000mm2 equivalent area; and
  2. there is an area of permanent opening between the two rooms as given in Diagram 3 based on at least the combined floor area of the habitable rooms.
5.16   A habitable room not containing openable windows may be ventilated through a conservatory (see Diagram 4) if:
  1. there is, from the conservatory to outside, provision for both: i.  purge ventilation, one or more ventilation openings, with a total area given in Diagram 4 based on at least the combined floor area of the habitable room and conservatory; and ii.   background ventilation, a ventilation opening (or openings) of at least 8000mm2 equivalent area; and
  2. there are openings (which must be closable) between the habitable room and the conservatory for: i.  purge ventilation equivalent to paragraph 5.15a(i) above; and ii.  background ventilation equivalent to paragraph 5.15a(ii) above which should be located typically at least 1.7 m above floor level and need not be within the door frame.

Section 6: New buildings other than dwellings – this section is omitted as it does not concern dwellings

Section 7: Work on existing buildings

General

FENSA do a Guide for Compliance with Building Regulations for replacement doors and windows in dwellings

7.1   When building work is carried out on an existing building, the work should comply with the applicable requirements of Schedule 1 to the Building Regulations, and the rest of the building should not be made less satisfactory in relation to the requirements than before the work was carried out (see regulations 3 and 4 of the Building Regulations). Further, when a building undergoes a material change of use, as defined in regulation 5 of the Building Regulations (see paragraph 3.17 above), Part F applies to the building or that part of the building which has been subject to the change of use, in accordance with regulation 6. Therefore, the guidance in other sections of this Approved Document may be applicable.

7.2   Windows are a controlled fitting. Regulation 4(1) of the Building Regulations requires that, when windows in an existing building are replaced, the replacement work should comply with the applicable requirements of Schedule 1, i.e. Parts L and N. In addition, the building work once completed should not have a worse level of compliance with other applicable requirements of Schedule 1 than before commencement of the work. Other applicable requirements of Schedule 1 may include Parts B, F and J.

7.3   Where the original windows were fitted with trickle ventilators the replacement windows should include them and they should be sized as set out in paragraph 7.6.

7.4   Where the original windows were not fitted with trickle ventilators and the room is not ventilated adequately by other installed provisions, it would be good practice to fit trickle ventilators (or an equivalent means of ventilation) to help with control of condensation and improve indoor air quality. Ventilation devices should be fitted with accessible controls.

7.5   When windows are replaced as part of the work connected with a material change of use, Sections 5 and 6 of this Approved Document apply.

7.6   In all cases where trickle ventilators (or an equivalent means of ventilation) are to be fitted, the new ventilation opening should not be smaller than was originally provided, and it should be controllable. Where there was no ventilation opening, or where the size of the original ventilation opening is not known, the following minimum sizes should be adopted.

Dwellings:
  • habitable rooms – 5000 mm2 equivalent area
  • kitchen, utility room and bathroom (with or without WC) – 2500 mm2 equivalent area.
Buildings other than dwellings:
  • occupiable rooms: for floor areas up to 10 m2 – 2500 mm2 equivalent area; greater than 10 m2 – at the rate of 250 mm2 equivalent area per m2 of floor area
  • kitchens (domestic type) – 2500 mm2 equivalent area
  • bathrooms and shower rooms – 2500 mm2 equivalent area per bath or shower
  • sanitary accommodation (and/or washing facilities) – 2500 mm2 equivalent area per WC.

Addition of a habitable room (not including a conservatory) to an existing dwelling

7.7   The requirements will be met by following the guidance in paragraphs 7.8 to 7.10.

7.8   The general ventilation rate for the additional room and, if necessary, adjoining rooms could be achieved by one of the following options.
  1. Background ventilators could be used as follows: i. if the additional room is connected to an existing habitable room which now has no windows opening to outside, the guidance in paragraph 5.15 should be followed; or ii. if the additional room is connected to an existing habitable room which still has windows opening to outside but with a total background ventilator equivalent area less than 5000 mm2, the guidance in paragraph 5.15 should be followed;or iii. if the additional room is connected to an existing habitable room which still has windows opening to outside and with a total background ventilator equivalent area of at least 5000 mm2, there should be background ventilators of at least 8000 mm2 equivalent area between  the two rooms and background ventilators of at least 8000 mm2 equivalent area between the additional room and outside.
  2. A single room heat recovery ventilator could be used to ventilate the additional habitable room . The supply rate to that room should be determined as follows. First, determine the whole building ventilation rate from Table 5.1b. Second, calculate the  room supply rate required from:

7.9  
For purge ventilation, follow the guidance given in Table 5.2a.
7.10   Guidance on location and controls is also given in Table 5.2a and guidance on performance testing standards is given in Table 5.3.

Addition of a wet room to an existing dwelling

7.11   The requirements for the additional wet room will be met by following the guidance in paragraphs 7.12 to 7.15.

7.12   Whole building and extract ventilation can be provided by:
  1. intermittent extract, as given in Table 5.2a, and a background ventilator of at least 2500 mm2 equivalent area; or
  2. single room heat recovery ventilator, as given in Table 5.2a; or
  3. passive stack ventilator, as given in Table 5.2b; or
  4. continuous extract fan, as given in Table 5.2c.

7.13   To ensure good transfer of air throughout the dwelling, there should be an undercut of minimum area 7600 mm2 in the internal door between the wet room and the existing dwelling. This is equivalent to an undercut of 10 mm for a standard 760 mm width door. This should be achieved by making an undercut of 10 mm above the floor finish if the floor finish is fitted, or by a 20 mm undercut above the floorboards, or other surface, if the finish has not been fitted.

7.14   For purge ventilation, follow the guidance for the appropriate system given in Tables 5.2a to 5.2c.

7.15   Guidance on location and controls is given in Tables 5.2a to 5.2c and guidance on performance standards is given in Table 5.3.

Addition of a conservatory to an existing building

7.16   The guidance applies to conservatories with a floor area over 30 m2.

7.17   The requirements will be met by following the guidance in paragraphs 7.18 to 7.20.

7.18   The general ventilation rate for the conservatory and, if necessary, adjoining rooms could be achieved by the use of background ventilators. Follow the guidance in paragraph 5.16 whatever the ventilation provisions in the existing room adjacent to the conservatory.

7.19   For purge ventilation, follow the guidance given in Table 5.2a.

7.20   Guidance on location and controls is also given in Tables 5.2a and guidance on performance standards is given in Table 5.3.

Refurbishing a kitchen or bathroom in an existing dwelling

7.21   If any of the work being carried out in the kitchen or bathroom of an existing building is ‘building work’, as defined in regulation 3 of the Building Regulations, the Regulations require that you comply with the appropriate requirements of the Regulations, and in doing so you do not make compliance with other requirements of the Regulations, including ventilation, worse than before. The Regulations also require that before you start work, the work is notified to a BCB, except in certain circumstances. (See paragraphs 3.4 to 3.10 inclusive above for details of notification requirements and exemptions.)

7.22   The definition of ‘building work’ in regulation 3 of the Building Regulations includes a range of building activities in existing buildings, and includes all work on controlled services. For more information see the Building Regulations 2010 at: www.planningportal.gov.uk.

7.23   If you carry out any ‘building work’, and there is an existing extract fan or passive stack ventilator (or cooker hood extracting to outside in the kitchen), you should retain or replace it. However, if there is no existing ventilation system you need not provide one. Replacing an extract fan or cooker hood with a similar type, and using the existing cabling, need not be notified to a BCB.

7.24   If a combustion appliance is installed, Approved Document J: Combustion appliances and fuel storage systems should be consulted. It is available at:

Section 8: Standards and other publications

Standards

BS EN 378-3:2008 Refrigerating systems and heat pumps. Safety and environmental requirements. Installation site and personal protection.

BSI PD CR 1752:1999 Ventilation for buildings – design criteria for the indoor environment.

BS 5502:2003 Buildings and structures for agriculture. Various relevant parts including: Part 33:1991 Guide to the control of odour pollution, AMD 10014 1998. Part 52:1991 Code of practice for design of alarm systems, emergency ventilation and smoke ventilation for livestock housing, AMD 10014 1998.

BS 5454:2000 Recommendations for the storage and exhibition of archival documents.

BS 5925:1991 Code of practice for ventilation principles and designing for natural ventilation. AMD 8930 1995.

BS 7913:1998 Principles of the conservation of historic buildings.

BS EN 13141-1:2004 Ventilation for buildings. Performance testing of components/products for residential ventilation. Externally and internally mounted air transfer devices.

BS EN 13141-3:2004 Ventilation for buildings. Performance testing of components/products for residential ventilation. Range hoods for residential use.

BS EN 13141-4:2004 Ventilation for buildings. Performance testing of components/products for residential ventilation. Fans used in residential ventilation systems.

BS EN 13141-6:2004 Ventilation for buildings. Performance testing of components/products for residential ventilation. Exhaust ventilation system packages used in a single dwelling.

BS EN 13141-7:2004 Ventilation for buildings. Performance testing of components/products for residential ventilation. Performance testing of a mechanical supply and exhaust ventilation units (including heat recovery) for mechanical ventilation systems intended for single family dwellings.

BS EN 13141-8:2006 Ventilation for buildings. Performance testing of components/products for residential ventilation. Performance testing of unducted mechanical supply and exhaust ventilation units [including heat recovery] for mechanical  ventilation systems intended for a single room.

BS EN 13986:2004 Wood-based panels for use in construction. Characteristics, evaluation of conformity and marking.

Other publications

American Conference of Government Industrial Hygienists (ACGIH)

Industrial ventilation 26th Edition, Manual of recommended practice. Available from: www.acgih.org/store

BRE

BRE Digest 464, Part 1:VOC emissions from building products. Sources, testing and emission data, 2002. ISBN 978 1 86081 546 1.

BRE Digest 464, Part 2:VOC emissions from building products. Control, evaluation and labelling schemes, 2002. ISBN 978 1 86081 547 8.

BSRIA

Ventilation hygiene toolkit:BSRIA Facilities Management Specification 1 Guidance to the standard specification for ventilation hygiene, 2002. ISBN 978 0 86022 454 9.

Chartered Institution of Building Services Engineers (CIBSE)

Applications Manual AM10: Natural ventilation in non-domestic buildings, 2005. ISBN 978 1 80328 756 0.

Applications Manual AM13: Mixed mode ventilation, 2000. ISBN 978 1 90328 701 4.

CIBSE Guide A: Environmental design, 2006.ISBN 978 1 90328 766 8.

CIBSE Guide B:Heating, ventilating, air conditioning and refrigeration, 2005. ISBN 978 1 90328 758 3.

TM13: Minimising the risk of Legionnaires’ disease, 2002. ISBN 978 1 90328 723 1.

CIBSE Commissioning Codes, available from: www.cibse.org/index.cfm?go=publications.view&item=266.

CIBSE TM26 Hygienic maintenance of office ventilation ductwork, 2000. ISBN 978 1 90328 711 8.

Defence Estates

Defence Works Functional Standard, Design and Maintenance Guide 08: Space requirements for plant access operation and maintenance, 1996. ISBN 978 1 11772 785 4. Available from:

www.defence-estates.mod.uk/publications/dmg/dmg_08.pdf    (this is now a broken link)

Department for Children, Schools and Families (DCSF);

Building Bulletin 101, Ventilation of school buildings, 2006. ISBN 978 0 11271 164 3.

See: www.teachernet.gov.uk/iaq        (this is now a broken link)

Department of Health Estates and Facilities Division

HTM 03; Part AVentilation in healthcare premises: Design and validation, 2007.

HTM 03; Part B – Ventilation in healthcare premises: Verification and operational Management, 2007.

HBN (various).

Energy Saving Trust

Good Practice Guide 192. Designing energy efficient multi-residential buildings, 1997.
Available from:
www.est.org.uk/bestpractice/index.cfm (archived).

Health and Safety Executive (HSE)

HSE Catering Information Sheet No 10, Ventilation of kitchens in catering establishments, 2007. Available from:
www.hsebooks.com.

HSE Catering Information Sheet No 11, The main health and safety law applicable to catering, 2000. Available from: www.hsebooks.com.

HSG 258 Controlling airborne contaminants at work. A guide to local exhaust ventilation (LEV), 2008. ISBN 978 0 71766 298 2.

HSG 193. COSHH Essentials. Accessed on:

www.coshh-essentials.org.ukHSG 202. General ventilation in the workplace – Guidance for employers, 2000. ISBN 978 0 71761 793 7.

L8 Legionnaires Disease: The control of legionella bacteria in water systems. Approved code of practice and guidance, 2000. ISBN 978 0 71761 772 2.

L24 Workplace (Health, Safety and Welfare) Regulations 1992. Approved Code of Practice and guidance , 2001. ISBN 978 0 71760 413 5.

HVCA

HVCA DW/144 Specification for sheet metal ductwork – low, medium and high pressure/air systems, 1998. ISBN 978 0 90378 327 9.

HVCA DW/154 Specification of plastics ductwork, 2000. ISBN: 0 90378 331 2.

HVCA DW/143 A practical guide to ductwork leakage testing, 2000. ISBN: 978 0 90378 330 9.

HVCA DW/172 Specification for kitchen ventilation systems, 2005.ISBN 978 0 90378 329 3.

HVCA TR/19 Guide to good practice. Internal cleanliness of ventilation systems, 2005. ISBN 978 0 90378 335 4.

Legislation

Factories Act 1961, Chapter 34.

Welfare of Farm Animals (England) Regulations 2000, SI 2000/1870.

Welfare of Farm Animals (England) (Amendment) Regulations 2002, SI 2002/1646.

Welfare of Farm Animals (England) (Amendment) Regulations 2003, SI 2003/299.

Department for Communities and Local Government

Planning Policy Statement (PPS) 15: Planning and the historic environment; DoE, 1994.
Paragraphs 6.1 to 6.40 have been superseded by Circular 01/2007, Revisions to principles of selection for listing buildings. Both available at:

www.communities.gov.uk/planningandbuilding/planning/planningpolicyguidance/historicenvironment/ppg15.   (this page is now archived)

Review of health and safety risk drivers (BD 2518). Available at:
www.communities.gov.uk/documents/planningandbuilding/pdf/reviewhealthsafety.pdf   (this page is now archived)

Appendix A: Performance-based ventilation

Introduction

see more on Ventilation

As specified in the section on Performance, this Approved Document recommends ventilation provisions to control both moisture and pollutants in buildings. In order to do this, acceptable levels of moisture and other pollutants need to be defined. This Appendix sets out the levels of moisture and other pollutants that the provisions in this Approved Document are designed to control.

Note that the guidance within this Approved Document may not be adequate to address pollutants from flueless combustion space heaters or from occasional, occupant-controlled events such as painting, smoking, cleaning or other high-polluting events. It does not address the airborne spread of infection or contamination from outdoor sources. While many of these considerations could be important factors in achieving acceptable indoor air quality, solutions are not ready for inclusion in this guidance, and indeed indoor air quality may be better controlled at source (e.g. avoidance, isolation or use of lower emitting products).

Performance criteria for dwellings

The performance criterion for moisture is as follows:

Oh, well, Hallelujah!

  • There should be no visible mould on external walls in a properly heated dwelling with typical moisture generation.
The principal performance criteria used for other indoor air pollutants are as follows.
Exposure to the following levels of nitrogen dioxide (NO2) should not be exceeded:
  • 288 μg/m3 (150 ppb) – 1 hour average (DOH, 2004)
  • 40 μg/m3 (20 ppb) – long-term average (DOH, 2004).
Exposure to the following levels of carbon monoxide should not be exceeded:
  • 100 mg/m3 (90 ppm) – 15 minute averaging time (DOH, 2004)
  • 60 mg/m3 (50 ppm) – 30 minute averaging time (DOH, 2004)
  • 30 mg/m3 (25 ppm) – 1 hour averaging time (DOH, 2004)
  • 10 mg/m3 (10 ppm) – 8 hours averaging time (DOH, 2004).

Exposure to total volatile organic compound (TVOC) levels should not exceed 300 μg/m3 averaged over 8 hours (ECA, 1992).

Control of bio-effluents (body odours) for adapted individuals (reduction in perception due to being exposed to the environment for a period of time) will be achieved by an air supply rate of 3.5 l/s/person (ASHRAE, 2003).

Mould growth can occur whether the dwelling is occupied or unoccupied, so the performance criteria for moisture (as set out in Table A2) should be met at all times, regardless of occupancy. The other pollutants listed above are harmful to the occupants only when the dwelling is occupied.

Assumptions used in applying performance criteria for dwellings in Section 5

General
  • For the default option in which the design air permeability can be any value, dwellings with ventilation System 1 or 2 are assumed to have an infiltration of 0.05 ach (air changes per hour); and dwellings with ventilation System 3 or 4 are assumed to have no infiltration.
  • For the alternative option in which the design air permeability is >5 m3/(h.m2) at 50 Pa, dwellings with ventilation System 1, 2 or 4 are assumed to have an infiltration of 0.15 ach, and dwellings with ventilation System 3 are assumed to have negligible infiltration, as discussed in Table 5.2c.
  • The ventilation effectiveness is 1.0.
  • For the purpose of this Approved Document, for all dwellings (new, and existing where Part F applies), the moisture criterion is likely to be met if the moving average surface water activity of the internal surfaces of external walls is always less than the value noted in Table A1 during the heating season, evaluated over each of the stated averaging periods. Table A1 is the primary basis for demonstrating compliance with the moisture criterion.

As a guide, for new dwellings, for the purpose of this Approved Document, the moisture criteria in Table A1 are likely to be met if the moving average relative humidity (RH) in a room is always less than the value given in Table A2 during the heating season, evaluated over each of the stated averaging periods.

The performance criterion for moisture (given above) is the same as that used in the 2006 edition of Approved Document F. However, research carried out since 2006 (Altamirano-Medina et al, 2009) has indicated that the values of relative humidity needed to satisfy the criterion could be expressed in a different and more practical way as shown in Table A2. These RH values may, in general, be slightly less onerous than those used in the 2006 edition. This may not be true in all cases and so the ventilation rates necessary to satisfy the criterion have not been changed.

Extract ventilation
  • The principal pollutant to be removed by extract ventilation is moisture. The source rates were taken from BS 5250:2002 Table B.1.
  • For intermittent extract: – Historically, a ventilation rate of 60 l/s has been specified in the kitchen for the removal of moisture and there is no strong justification to amend it. The ventilation rate removes moisture generated at a production rate of 2000 g/h. A reduced ventilation rate of 30 l/s is used for a cooker hood, owing to the greater ventilation effectiveness. – Historically, a ventilation rate of 15 l/s has been specified in the bathroom for the removal of moisture and there is no strong justification to amend it. The ventilation rate removes moisture generated at a production rate of 400 g/h. – In the utility room, it is assumed that the ventilation rate required is 50% of that in the kitchen. – In WCs, the main pollutant is odour. Historically, a ventilation rate of 6 l/s has been specified and there is no strong justification to amend it.
  • For continuous extract:– No reason has been found to change the extract rates, so the rates used in Table 5.1a are the same as used in the 2006 edition of AD F.
Whole dwelling ventilation
  • The principal pollutant to be removed by whole dwelling ventilation is moisture. The source rates were taken from BS 5250:2002 Table B.1.
  • It was assumed that local extract removes 100% of the moisture generated in the bathroom and 50% of the moisture generated in the kitchen.
  • The rates given in Table 5.1b are the same as in the 2006 edition.
  • The calculations were based on winter weather conditions. During warmer spring and autumn periods, the moisture removal capacity of the outdoor air will be less (i.e. the outdoor air on being heated to the internal temperature within the dwelling will have a higher relative humidity in the spring and autumn periods) and additional ventilation may be required. The provisions for purge ventilation (e.g. windows) may be used for this purpose.
  • There are other pollutants which must also be adequately controlled. These are particularly important in homes of low occupant density where moisture production is low for the size of the property. Levels of volatile organic compounds were monitored in a BRE study of UK homes (Dimitroulopoulou et al, 2005). From these data, the total source production rate of volatile organic compounds was determined to be 300 μg/h per m2 of floor area. To meet the performance criterion of 300 μg/m3, it requires a minimum whole dwelling ventilation rate of 0.3 l/s per m2 of internal floor area.
Purge ventilation
  • A value of 4 ach has been selected as: – it provides a purge ventilation rate an order of magnitude above whole building ventilation; – it is similar to the ventilation rate provided by windows in the 1995 edition of Approved Document F. The calculation assumes single-sided ventilation for a dwelling in an urban environment and an internal/external temperature difference of 3°C.

Basis of Table 5.2 – Whole dwelling ventilation rates

  • In determining the ventilation rates, the air supply rates in Table 5.1b have been used.
  • For dwellings having an air permeability of > 5 m3/(h.m2) at 50 Pa, the air supply rate has been reduced by 0.15 ach to allow for infiltration.
  • To determine the equivalent areas, the standard air flow equation has been used as below:

A = 1000.(Q/Cd).(ρ/2.∆P)0.5

Where:

A = the background ventilator equivalent area (mm2)

Q = the air supply rate (l/s)

Cd = the discharge coefficient, taken as 0.61

ρ = the air density (kg/m3), taken as 1.2

∆P = the pressure across the vent, which has been taken as 0.6 Pa for single-storey dwellings and 1.0 Pa for multi-storey dwellings.

Note that the total actual equivalent area required (AT) is double that derived from the equation above, which provides the equivalent area only for air supplied to the dwelling. A similar equivalent area is required for air to exit the dwelling. The total equivalent area determined in this way is given in the guidance for Systems 1 and 2. Note that in determining these pressure differences, a meteorological wind speed of 4 m/s at 10 m height was taken (based on BS 5925:1991) and an internal/external temperature difference of 15°C

Performance criteria for buildings other than dwellings

The main guidance within this document has focused on offices. For this, the main criteria have been:

  • A supply rate, in the absence of tobacco smoking or other excessive pollutants, of 10 l/s/person, based upon surveys which indicate that below this level the incidence of health effects becomes increasingly significant. This will also satisfy the requirement of 8 l/s/person needed to control bio-effluents for unadapted individuals.
  • There should be no visible mould on external walls in a properly heated building with typical moisture generation.
  • Exposure to the following levels of nitrogen dioxide (NO2) should not be exceeded:
    – 288 μg/m3 (150 ppb) – 1 hour average (Department of the Environment, 1996)
    – 40 μg/m3 (21 ppb) – annual mean (WHO, 2005).
  • Exposure to the following levels of carbon monoxide should not be exceeded:
    – 100 mg/m3 (90 ppm) – 15 minute averaging time (WHO, 2000)
    – 60 mg/m3 (50 ppm) – 30 minute averaging time (WHO, 2000)
    – 30 mg/m3 (25 ppm) – 1 hour averaging time (WHO, 2000)
    – 10 mg/m3 (10 ppm) – 8 hours averaging time (Department of the Environment,1994a).
  • Exposure to the following levels of carbon monoxide for occupational exposure should not be exceeded:
    – 35 mg/m3 (30 ppm) – 8 hours averaging time (HSE, 2003).
  • Exposure to total volatile organic compound (TVOC) levels should not exceed 300 μg/m3 averaged over 8 hours (ECA, 1992).
  • Ozone levels should not exceed 100 μg/m3 (Department of the Environment, 1994b).

Note that the guidance within this Approved Document may not be adequate to address pollutants from occasional, occupant-controlled events such as painting, smoking, cleaning or other high-polluting events. While these could be important factors in achieving acceptable indoor air quality, solutions are not ready for inclusion in this guidance, and indeed they may be better controlled at source (e.g. avoidance, isolation or use of lower emitting products).

Mould growth can occur whether the building is occupied or unoccupied, so the performance criteria for moisture (as set-out in Table A1) should be met at all times, regardless of occupancy. The other pollutants listed above are harmful to the occupants only when the building is occupied.

Where the Health and Safety Executive gives guidance for specific situations, it should be followed in preference to the guidance given here.

Assumptions used in applying performance criteria for offices in Section 2 General

  • The office has an air permeability of 3 m3/(h.m2) at 50 Pa.
  • At this level of air permeability, in large buildings (low ratio of surface area to volume contained), infiltration can be assumed to be negligible compared with the purpose-provided ventilation.
  • The ventilation effectiveness is 0.9 (for Table 6.1b).
  • For the purposes of this Approved Document, the moisture criterion will be met if the surface water activity in a room does not exceed the values given in Table A1 during the heating season.
Extract ventilation
  • Office equipment can emit pollutants including ozone and organic compounds. For example, a study by Black and Wortham (1999) suggests the following emission rates for laser printers and dry paper copiers assuming 30 minutes use in an hour:
    –25 mg/h for TVOCs
    – 3 mg/h for ozone.

To meet the performance criteria for these pollutants requires an extract rate of 20 l/s per machine during use.

  • For sanitary accommodation, the extract rates used for dwellings have been applied.
  • For food and beverage preparation areas, the extract rates used for dwellings have been applied.
Whole building ventilation
  • A number of studies have investigated ventilation and health in offices (principally sick building syndrome). Although there is no clear threshold ventilation rate below which health suddenly worsens, a number of sources have identified 10 l/s/p as a significant level. This can probably be traced back to an analysis of experimental studies of office buildings by Mendell (1993). Hence the recommendation within the Approved Document is for 10 l/s/p for buildings with no smoking and no significant pollutant sources.
  • Increasing the ventilation rate above 10 l/s/p may improve health (results unclear), but there are diminishing returns (i.e. the improvement in health per l/s/p increase in ventilation rate becomes smaller as the ventilation rate increases). This suggests that there is little advantage in increasing the whole building ventilation rate above 10 l/s/p. Increased ventilation has a cost in economic and environmental terms. Having set a ventilation rate of 10 l/s/p, if further improvements in indoor air quality are necessary, alternative approaches should be considered first, e.g. use of low-emission materials.

Purge ventilation

    •  There are normally more options for the removal of high concentrations of pollutants from office spaces than for dwellings (e.g.leaving rooms unoccupied until acceptable pollutant levels are achieved). Hence, general guidance has been provided rather than specifying any ventilation rate(s).

References
Altamirano-Medina H., Mumovic D., Davies M., Ridley I. and Oreszczyn T., (2009). Guidelines to avoid mould growth in buildings, Advanced Buildings Energy Research, 3, pp 221–236.
ASHRAE. Handbook 2007: HVAC applications.

Black M S and Wortham A W (1999). Emissions from office equipment. Proceedings of the 8th International Conference on Indoor Air Quality and Climate, Indoor Air 99, Edinburgh 8–13 August 1999, Vol. 2, pp 455–459.

BS 5250:2002 Code of practice for the control of condensation in buildings. BSI.

BS 8233:1999 Code of Practice: Sound insulation and noise reduction for buildings, BSI.

Department of the Environment (1994a). Expert panel on air quality standards: Carbon monoxide.London, HMSO. www.defra.gov.uk/environment/airquality/panels/aqs/publications/index.htm     (this page is now archived)

Department of the Environment (1994b). Expert panel on air quality standards: Ozone. London, HMSO. www.defra.gov.uk/environment/airquality/panels/aqs/publications/index.htm     (this page is now archived)

Department of the Environment (1996). Expert panel on air quality standards: Nitrogen dioxide. London, The Stationery Office.
www.defra.gov.uk/environment/airquality/panels/aqs/publications/index.htm     (this page is now archived)

Department of Health (2004). Committee on the Medical Effects of Air Pollutants. Guidance on the effects on health of indoor air pollutants.

www.advisorybodies.doh.gov.uk/comeap/PDFS/guidanceindoorairqualitydec04.pdf     (this link is now broken)

Dimitroulopoulou C, Crump D, Coward S K D, Brown V, Squire R, Mann H, White M, Pierce B and Ross D (2005). Ventilation, air tightness and indoor air quality in new homes. Report BR 477. BRE bookshop.

ECA (1992). European Concerted Action on indoor air and its impact on man: Guidelines for ventilation requirements in buildings.Working Group Report No. 11. EUR 14449 EN. Commission of the European Communities, Luxembourg.

HSE (2003). Occupational exposure limits 2002, plus supplement 2003. HSE Books.

Mendell M J (1993). Non-specific symptoms in office workers: a review and summary of the epidemiologic literature. Indoor Air 3, pp 227–236.

Ross D I and Wilde D (1999). Continuous monitoring of nitrogen dioxide and carbon monoxide levels in UK homes. Proceedings of the 8th International Conference on Indoor Air Quality and Climate, Indoor Air 99, Edinburgh 8-13 August 1999, Vol. 3, pp 147–152.

WHO (2000). Guidelines for air quality. World Health Organisation, Geneva.

WHO (2005). Air quality guidelines – global update. World Health Organization, Geneva.

Appendix B: Purge ventilation

 

Introduction

Adequate purge ventilation may be achieved by the use of openable windows and/or external doors. This Appendix provides details of necessary window and door sizes. The diagrams highlight the window dimensions of importance.

Windows

  • For a hinged or pivot window that opens 30º or more or for parallel sliding windows (e.g. vertical sliding sash windows), the height x width of the opening part should be at least 1/20th of the floor area of the room.
  • For a hinged or pivot window that opens between 15º and 30º, the height x width of the opening part should be at least 1/10th of the floor area of the room.
  • If the window opens less than 15º it is not suitable for providing purge ventilation and other arrangements should be made.
  • If the room contains more than one openable window, the areas of all the opening parts may be added to achieve the required proportion of the floor area. The required proportion of the floor area is determined by the opening angle of the largest window in the room.
  • Note that Approved Document B includes provisions for the size of escape windows.The larger of the provisions in Approved Document B or F should apply in all cases.

External doors (including patio doors)

  • For an external door, the height x width of the opening part should be at least 1/20th of the floor area of the room. If the room contains more than one external door, the areas of all the opening parts may be added to achieve at least 1/20th of the floor area of the room.
  • If the room contains more than one external door, the areas of all the opening parts may be added to achieve at least 1/20th of the floor area of the room.
  • If the room contains a combination of at least one external door and at least one openable window, the areas of all the opening parts may be added to achieve at least 1/20th of the floor area of the room.

 

Further information

The aim of this guidance is to achieve a purge ventilation rate of 4 ach.
  • It provides a purge ventilation rate of an order of magnitude above the whole building ventilation rate.
  • It is similar to the purge ventilation rate provided by windows historically in ADF.

The guidance contained within this Appendix is a simplification of guidance in BS5925:1991 (AMD 8930, 1995) Code of practice for ventilation principles and designing for natural ventilation. This Appendix has assumed single-sided ventilation for dwellings in an urban environment (local wind speed of 2.1m/s) and a summer-time internal/external temperature difference of 3°C. It has considered and simplified variations in air flow rates caused by factors including window type and window height.

This design guidance should deliver 4 ach in most cases. Depending on the dwelling design or the external climate, it may be possible to achieve this ventilation rate through a smaller window opening area. BS5925 provides a good starting point for determining the window openings required. It may be beneficial to also seek expert advice.

Appendix C: Example calculations for ventilation sizing for dwellings

Introduction

This Appendix provides example calculations for each ventilation system set out in paragraph 5.10. A ground-floor flat and a semi-detached house have been considered for each system type. Thus there are eight examples as follows.

Ground-floor flat:

Example C1 – Background ventilators and intermittent extract fans

Example C2 – Passive stack ventilation

Example C3 – Continuous mechanical extract

Example C4 – Continuous mechanical supply and extract

Semi-detached house:

Example C5 – Background ventilators and intermittent extract fans

Example C6 – Passive stack ventilation

Example C7 – Continuous mechanical extract

Example C8 – Continuous mechanical supply and extract

It has been assumed that the intended measured air permeability is > 5 m3/(h.m2) in examples C1, C2, C5 and C6, and the design air permeability is ≤ 3 m3/(h.m2) in the other examples.

Details of ground-floor flat

Description

The flat contains the following rooms:

  • kitchen
  • combined living/dining room
  • one double bedroom
  • internal bathroom containing WC, and in addition
  • all rooms have an external wall except for the bathroom.

The floor plan is given in Diagram C1.

Assumptions:

  • cooker hood adjacent to cooker hob
  • gross internal volume of the heated space of 83 m3
  • total floor area of 36 m2
  • two-person occupancy and
  • side-hinged windows 1.0 m high and openable to 60°.

Details of semi-detached house

Description

The semi-detached house contains the following rooms:
  • entrance hall/stairway
  • kitchen
  • dining room
  • living room
  • three bedrooms
  • bathroom containing WC, and in addition
  • all rooms have an external wall.

The floor plans are given in Diagrams C2 and C3.

Assumptions

  • cooker hood adjacent to cooker hob
  • gross internal volume of the heated space of 210 m3
  • total floor area of 84 m2
  • four-person occupancy
  • side-hinged windows 1.0 m high and openable to a fixed position of 20º.

Appendix D: Minimising ingress of external pollution into buildings in urban areas

Typical urban pollutants that need to be considered include those covered by the UK Air Quality Strategy (www.defra.gov.uk/environment/airquality/strategy/index.htm (2007)). These are:
  • carbon monoxide, CO
  • nitrogen dioxide, NO2
  • sulphur dioxide, SO2
  • ozone, O3
  • particles (PM10)
  • benzene
  • 1,3-butadiene
  • polycylic aromatic hydrocarbons (PAHs)
  • ammonia
  • lead.
Although nitrogen oxide, NO, is not included in the UK Air Quality Strategy, it is a normal constituent of combustion discharges and in many cases (for example, from gas-fired plant) the largest polluting emitter. Therefore, it also needs to be taken into account. Typical pollution emission sources that need to be considered include:
  • including traffic junctions and underground car parks
  • combustion plant (such as heating appliances) running on conventional fuels, most commonly natural gas
  • other combustion processes (for example, waste incineration, thermal oxidation abatement systems)
  • discharges from industrial processes
  • fugitive (i.e. adventitious/not effectively controlled) discharges from industrial processes and other sources
  • building ventilation system exhaust discharges
  • construction and demolition sites which are a source of particles and vapourous discharges.

In urban areas, buildings are exposed simultaneously to a large number of individual pollution sources from varying upwind distances (long range, intermediate range and short range) and heights and also over different timescales. The relationship between these and their proportionate contribution under different circumstances governs pollutant concentrations over the building shell and also internally.

Internal contamination of buildings from outdoor pollution sources therefore depends upon the pollutant sources, the physical characteristics of the building and its relation to its surroundings, the ventilation strategy employed and the location of the air intake. Whatever type of ventilation system is used, it is important to ensure that the intake air is not contaminated. This is especially important in air quality management areas where, by definition, pollution levels of at least one pollutant are already close to the air quality standards. Simplified guidance on ventilation intake placement for minimising ingress of pollutants may be summarised, as in Table D1.

Control of ventilation intakes

For pollutant sources such as urban road traffic, whose concentration fluctuates with the time of day, reducing the flow of external air or closing ventilation intakes during peak periods of high external pollutant concentrations, for example during rush hours, for up to an hour may be an option.

Air intakes located on a less polluted side of the building may then be used for fresh air, or air may be fully recirculated within the building. Alternatively, the building may be used as a ‘fresh air’ reservoir to supply air during these short periods. The use of atria as a source of ‘fresh air’ for this purpose may be an option.

However, care must be taken since, for example, reducing the inflow of external air will also reduce the outflow of internal air, resulting in a build-up of internally generated pollutants that need to be removed. Most modern buildings have low ceiling heights and therefore the concept of a substantial ‘fresh air’ reservoir available within the building may not apply. Further details of this principle with examples may be found in Liddament (2000).

Location of exhaust outlets

The location of exhausts is as important as the location of air intakes. These should be located such that re-entry to a building, or ingestion into other nearby buildings, is minimised (for both natural and mechanical intakes) and such that there is no adverse effect on the surrounding area. Guidance on outlet placement may be summarised as follows:
  • Exhausts should be located downstream of intakes where there is a prevailing wind direction
  • Exhausts should not discharge into courtyards, enclosures or architectural screens as pollutants tend to build up in such spaces and do not disperse very readily
  • It is recommended that stacks should discharge vertically upwards and at high level to clear surrounding buildings and so that downwash does not occur
  • Where possible, pollutants from stacks should be grouped together and discharged vertically upwards. The increased volume will provide greater momentum and increased plume height. This is common practice where there are a number of fume cupboard discharges; greater plume height dispersion can be achieved by adding the general ventilation exhaust.

References

CIBSE (1999). CIBSE Technical Memorandum TM21, Minimising pollution at air intakes.

ISBN 978 0 90095 391 0.

Liddament MW (2000) Chapter 13: ‘Ventilation strategies’,
Indoor Air Quality Handbook.
McGraw-Hill.

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