12.1 For an existing dwelling with a total useful floor area of over 1000m2, additional work may be required to improve the overall energy efficiency of the dwelling if proposed work consists of or includes any of the following.
a. An extension.
b. Providing any fixed building service in the dwelling 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 dwelling complies with Part L of the Building Regulations, to the extent that they are technically, functionally and economically feasible.
12.2 Technical guidance on consequential improvements is given in Approved Document L, Volume 2: Buildings other than dwellings.
