12.1 For an existing building with a total useful floor area of over 1000m2, additional work may be required to improve the overall energy efficiency of the building if proposed work consists of or includes any of the following.

a. An extension.

b. Providing any fixed building service in the building for the first time.

c. Increasing the capacity of any fixed building service (which does not include doing so on account of renewable technology).

Consequential improvements should be carried out to ensure that the entire building complies with Part L of the Building Regulations to the extent that they are technically, functionally and economically feasible.

NOTE: If the building already complies with the current requirements of Part L of the Building Regulations, consequential improvements are not required.

12.2 Where work other than the items listed in paragraph 12.1 is planned as part of the principal works, if they improve the energy performance of the building, these are consequential improvements. Work carried out to compensate for the poorer standard of an extension using the alternative approach to demonstrating compliance described in paragraph 10.11 does not count as a consequential improvement.

Consequential improvements which apply when extending a building

NOTE: A new free-standing building constructed on an existing site is a new building, not an extension.

12.3 When an existing building with a total useful floor area of over 1000m2 is being extended or the habitable area is being increased, consequential improvements should be installed. The measures listed in Appendix D, Table D1, may be considered technically, functionally and economically feasible in normal circumstances.

12.4 For an extension or increase in habitable area, the value of the principal works is used to determine the minimum value of the consequential improvement works. The value of the consequential improvement works should not be less than 10% of the value of the principal works.

12.5 As part of the initial notice or deposit of plans, a chartered quantity surveyor or other suitably qualified person should produce a signed report that establishes the value of the principal works and the value of the consequential improvements using prices current at the date when the building control body is informed of the proposals.

Consequential improvements on installing or extending the capacity of fixed building services

NOTE: Increasing the size of central boiler plant to serve a new extension would not generally increase the installed capacity of a fixed building service per unit area, unless the heating provision in the existing building was also increased at the same time. In these circumstances, paragraph 12.6 would not apply, but paragraphs 12.3 to 12.5 would continue to apply as a result of the extension.

12.6 If it is proposed to install a fixed building service in an existing building with a total useful floor area of over 1000m2, either as a first installation or as an installation that increases the installed capacity of a fixed building service per unit area, then both of the following should be implemented as consequential improvements.

a. Make energy efficiency improvements to the fixed building services to meet the requirements of Part L, where this is practical and technically, functionally and economically feasible.

i. When installing or extending the capacity of fixed building services, the value of the principal works is used to determine the minimum value of the energy efficiency improvements made to fixed building services as consequential improvements. The value of these consequential improvements should not be less than 10% of the value of the principal works, excluding the value of any work to improve other energy efficiency aspects of the building served by the services in meeting paragraph 12.6b.

ii. The measures listed in Appendix D, Table D1, relate to this requirement, and may be considered technically, functionally and economically feasible in normal circumstances.

iii. As part of the initial notice or deposit of plans, a chartered quantity surveyor or other suitably qualified person should produce a signed report that establishes the value of the principal works and the value of the consequential improvements using prices current at the date when the building control body is informed of the proposals.

b. Improve other energy efficiency aspects of those parts of the building served by the fixed building service to meet the requirements of Part L, where this is technically, functionally and economically feasible.

i. All technically, functionally and economically feasible measures to improve the fabric of the building served by the service should be implemented. The extent of the improvements to the fabric should not be determined by the value of the principal works.

ii. The measures in Appendix D, Table D2 relate to this requirement and may be considered technically, functionally and economically feasible in normal circumstances.

Section 12: Consequential improvements