Summary
0.1 This approved document, Approved Document L, Volume 1: Dwellings, gives guidance on how to comply with Part L of Schedule 1 to the Building Regulations and the energy efficiency requirements for dwellings. For guidance relating to non-domestic buildings, use Approved Document L, Volume 2: Buildings other than dwellings.
0.2 This approved document contains the following sections:
Application
0.3 The guidance in Approved Document L, Volume 1 applies to dwellings only.
In a mixed-use building, Approved Document L, Volume 2: Buildings other than dwellings should be consulted for building work in parts of the building that are not dwellings.
NOTE: Dwellings are self-contained units. Rooms for residential purposes and buildings that contain only rooms for residential purposes are not dwellings; Approved Document L, Volume 2: Buildings other than dwellings applies.
Common areas in buildings that contain multiple dwellings
0.4 For the common areas of buildings that contain more than one dwelling, the following guidance applies.
a. If the common areas are heated, the guidance in Approved Document L, Volume 2: Buildings other than dwellings should be followed.
b. If the common areas are unheated, individual fabric elements should meet the minimum standards set out in Section 4.
New dwellings
0.5 Guidance for new dwellings is given in Sections 1 to 9 of this approved document, Approved Document L, Volume 1.
0.6 For a conservatory or porch installed as part of the construction of a new dwelling, the treatment of the conservatory or porch depends on whether both of the following have been achieved.
a. There is adequate thermal separation between the dwelling and the conservatory or porch.
b. The dwelling’s heating system is not extended into the conservatory or porch.
If both (a) and (b) have been achieved, the conservatory or porch should be treated as if it were an extension being added onto an existing dwelling. The guidance for new elements in existing dwellings in Section 10 should be followed.
If either or both of (a) or (b) has not been achieved, the conservatory or porch should be treated as a room in the new dwelling. The guidance for the whole new dwelling should be followed, including for dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate calculations.
Extensions to and work on existing dwellings
0.7 Guidance for existing dwellings is given in this approved document for the following.
a. Limiting heat gains and losses: Section 4.
b. Building services: Sections 5 and 6.
c. New elements in existing dwellings, including replacing a fabric element and constructing an extension: Section 10.
d. Existing elements in existing dwellings, including renovating or retaining a thermal element, material change of use and change to energy status: Section 11.
NOTE: For building work in very large dwellings of over 1000m2, consequential improvements may be required to improve the energy efficiency of the dwelling. Guidance is given in Section 12.
Exemptions for listed buildings, buildings in conservation areas and scheduled monuments
0.8 Work to the following types of dwellings does not need to comply fully with the energy efficiency requirements where to do so would unacceptably alter the dwelling’s character or appearance.
a. Those listed in accordance with section 1 of the Planning (Listed Buildings and Conservation Areas) Act 1990.
b. Those in a conservation area designated in accordance with section 69 of the Planning (Listed Buildings and Conservation Areas) Act 1990.
c. Those included in the schedule of monuments maintained under section 1 of the Ancient Monuments and Archaeological Areas Act 1979.
0.9 Work to a dwelling in paragraph 0.8 must comply with the energy efficiency requirements where this would not unacceptably alter the dwelling’s character or appearance. The work should comply with standards in this approved document to the extent that it is reasonably practicable.
Historic and traditional dwellings
0.10 The energy efficiency of historic and traditional dwellings should be improved only if doing so will not cause long-term deterioration of the building’s fabric or fittings. In particular, this applies to historic and traditional buildings with a vapour permeable construction that both absorbs moisture and readily allows moisture to evaporate. Examples include those built with wattle and daub, cob or stone and constructions using lime render or mortar.
0.11 New extensions to historic and traditional dwellings should comply fully with the energy efficiency standards in this approved document unless there is a need to match the external appearance or character of the extension to that of the host building. The work should comply with standards in this approved document to the extent that it is reasonably practicable.
0.12 In determining whether full energy efficiency improvements should be made, the building control body should consider the advice of the local authority’s conservation officer.
0.13 Additional guidance is available in Historic England’s Energy Efficiency and Historic Buildings:
Application of Part L of the Building Regulations to Historic and Traditionally Constructed Buildings.
Exemptions for conservatories and porches
0.14 Where a dwelling is extended by adding a conservatory or porch, the work is exempt from the energy efficiency requirements, under regulation 21 of the Building Regulations, if all of the following apply.
a. The extension is at ground level.
b. The floor area of the extension does not exceed 30m2.
c. The glazing complies with Part K of Schedule 1 to the Building Regulations.
d. Any wall, door or window that separates the extension from the dwelling has been retained or, if removed, has been replaced with a wall, door or window.
NOTE: Replacement walls, windows and doors should meet the requirement in regulation 23(2). See Section 10.
e. The heating system of the dwelling is not extended into the conservatory or porch.
Exemptions for covered areas
0.15 Where a dwelling is extended by adding a carport that is open on at least two sides, a covered yard, a covered walkway or a covered driveway, the work is exempt from the energy efficiency requirements if both of the following apply.
a. The extension is at ground level.
b. The floor area of the extension does not exceed 30m2.
Live/work units
0.16 A building that contains both living accommodation and space for commercial purposes (e.g. for a workshop or office) should be treated as a dwelling if the commercial part can be reverted to domestic use.
0.17 The commercial part of a building can be reverted to domestic use if all of the following apply.
a. There is direct access between the commercial space and the living accommodation.
b. The commercial space and the living accommodation are within the same thermal envelope.
c. The living accommodation comprises a substantial proportion of the total area of the unit. What constitutes a ‘substantial proportion’ should be assessed on a case-by-case basis by the building control body.
NOTE: A large non-domestic building that contains a small flat for a manager is not treated as a dwelling. A dwelling that contains a room used as an office or utility space is still treated as a dwelling.
Mixed-use developments
0.18 When constructing a dwelling as part of a larger building that contains other types of accommodation, sometimes called a mixed-use development, refer to the two volumes of Approved Document L as follows.
a. For guidance on each individual dwelling, use this approved document, Approved Document L, Volume 1: Dwellings.
b. For guidance on the non-dwelling parts of the building, such as heated common areas and any commercial or retail space, use Approved Document L, Volume 2: Buildings other than dwellings.
Selected key interactions with other parts of the Building
Regulations
0.19 The approved documents set out what, in ordinary circumstances, may be accepted as one way to comply with the Building Regulations. Those designing or undertaking building work remain responsible for assessing, on a case-by-case basis, whether specific circumstances require additional or alternative measures to achieve compliance with the regulatory requirements. There are interactions between many of the requirements of the Building Regulations. Guidance on some key interactions is given below.
Interaction with Part C
0.20 This approved document, Approved Document L, Volume 1, provides guidance and examples on upgrading thermal elements. For interstitial and surface condensation, a lesser standard may be acceptable. Guidance in Approved Document C should be followed.
Interaction with Part E
0.21 This approved document, Approved Document L, Volume 1, provides guidance on insulation that is reasonably continuous and limits thermal bridging. Construction junctions should limit noise transfer where Part E of the Building Regulations sets a requirement. Approved Document E should be followed.
Interaction with Part F
0.22 This approved document, Approved Document L, Volume 1, provides guidance on reducing unwanted heat loss, by achieving optimum airtightness. When specifying the minimum amount of purpose-provided ventilation, consider the air infiltration of a dwelling; follow Approved Document F.
Interaction with Part J
0.23 This approved document, Approved Document L, Volume 1, provides guidance on airtightness. For guidance on permanent ventilation openings for open flued appliances in very airtight dwellings, follow Approved Document J.
Interaction with Part K and Part M
0.24 This approved document, Approved Document L, Volume 1, provides guidance on controls for fixed building services and on-site electricity generation. Manual controls, where provided, should be within reasonable reach of the occupants. Follow the guidance in Approved Documents K and M.
