Section 3 General guidance

General guidance

  1. Key terms
    1. Types of work covered by this Approved Document
      1. Exemptions
        1. Notification of work covered by the ventilation requirements
          1. Competent person self-certification schemes
            1. Emergency repairs
              1. Minor works
              2. Historic and traditional buildings
                1. Material change of use
                  1. Live-work units
                    1. Mixed use developments
                      1. Materials and workmanship
                        1. Independent certification schemes
                          1. Standards and technical specifications
                            1. The Workplace (Health, Safety and Welfare) Regulations 1992

                              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.

                              Diagram 1 Provisions for background ventilation

                              Diagram 1 Provisions for background ventilation

                              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:

                              a. 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;

                              b. 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;

                              c. greenhouses providing that the principal purpose of the building is not retailing, packing or exhibiting;

                              d. 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;

                              e. temporary buildings not intended to remain in place for more than 28 days;

                              f. 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;

                              g. 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;

                              h. 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;

                              i. detached buildings of less than 15 m2 floor area containing no sleeping accommodation; and

                              j. 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

                              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:

                              a. listed buildings;

                              b. buildings in conservation areas;

                              c. 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;

                              d. 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

                              e. 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 Heritage1 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:

                              a. restoring the historic character of a building that has been subject to previous inappropriate alteration, e.g. replacement windows, doors and rooflights;

                              b. rebuilding a former historic building (e.g. following a fire or filling a gap site in a terrace);

                              c. 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

                              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:

                              a. the building or part of a building is used as a dwelling, where previously it was not;

                              b. the building or part of a building contains a flat, where previously it did not;

                              c. the building or part of a building is used as a hotel or a boarding house, where previously it was not;

                              d. the building or part of a building is used as an institution, where previously it was not;

                              e. the building or part of a building is used as a public building, where previously it was not;

                              f. the building or part of a building is not a building described in Classes 1 to 4 in Schedule 2, where previously it was;

                              g. 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;

                              h. the building or part of a building contains a room for residential purposes, where previously it did not;

                              i. 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

                              j. 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:

                              a. there is direct access between the commercial space and the living accommodation; and

                              b. both are contained within the same thermal envelope; and

                              c. 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 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.

                              Independent certification schemes

                              3.24There are many uK product certification schemes. Such schemes certify compliance with the requirements of a recognised standard that is appropriate to the purpose for which the material is to be used. Materials which are not so certified may still conform to a relevant standard.

                              3.25Many certification bodies that approve products under such schemes are accredited by the united Kingdom Accreditation Service (uKAS). Such bodies can issue certificates only for the categories of product covered under the terms of their accreditation.

                              3.26BCBs may take account of the certification of products, components, materials or structures under such schemes in deciding whether the relevant standard has been complied with. Similarly, BCBs may take account of the certification of the installation or maintenance of products, components, materials or structures under such schemes in deciding on compliance with the relevant standard. Nonetheless, before accepting that certification constitutes compliance with building regulations, a BCB should establish in advance that the relevant scheme is adequate for that purpose.

                              Standards and technical specifications

                              3.27Building regulations are made for specific purposes, including securing the health, safety, welfare and convenience of people in or about buildings; furthering the conservation of fuel and power; furthering the protection or enhancement of the environment; and facilitating sustainable development. Guidance contained in standards and technical approvals is relevant to the extent that it relates to those purposes. However, the guidance may also address other aspects of performance such as serviceability, or aspects which, although they relate to health and safety, are not covered by building regulations.

                              3.28When an Approved Document makes reference to a named standard or document, the relevant version of the standard or document is the one listed at the end of the Approved Document. until the reference in the Approved Document is revised, the standard or document listed remains the approved source, but if the issuing body has published a revised or updated version, any content that addresses the relevant requirements of the Building

                              3.29The appropriate use of a product in compliance with a European Technical Approval as defined in the Construction Products Directive will meet the relevant requirements.

                              3.30The Department intends to issue periodic amendments to its Approved Documents to reflect emerging harmonised European standards. Where a national standard is to be replaced by a European harmonised standard, there will be a coexistence period during which either standard may be referred to. At the end of the coexistence period the national standard will be withdrawn.

                              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.