APPROVED DOCUMENT L2B – EXISTING BUILDINGS OTHER THAN DWELLINGS


Consequential improvements

When carrying out building works, there is now a requirement to make additional improvements to the fabric and services of existing buildings in order to reduce energy consumption.

However, this requirement only applies to existing buildings > 1000m2 where the work consists of;
a)
an extension
b)
initial provision of any fixed building service
c)
an increase in the installed capacity of any fixed building services (eg. to increase the heating output)

If it is proposed to build an extension, then a range of measures must be adopted to at least 10% of the value of the principal works.

When installing building services as a first installation or where the installation increases the installed capacity per unit area of an existing service then improvements must be made to the building fabric (walls, floors, roof, windows) and these are not limited to the 10% value. In addition, it will also be necessary to carry out further improvements as for extensions.


Large Extensions

If the extension is greater than 100m2 and at least 25% of the existing building, then it should be considered as a new building and the guidance in Approved Document L2A followed. It should be noted, however, that there will still be a need to carry out consequential improvements.


Smaller extensions
a)
A simple method of showing compliance is to meet the minimum fabric insulation standards and limit the area of windows etc.


Or
b)
The CO2 emissions from the building must be calculated and compared to a notional building that satisfies the requirements of a) above.
Conservatories and substantially glazed extensions

Non-exempt conservatories and sun rooms must meet the thermal standards for elements required for extensions, although there is no limit on the amount of glazing permitted.


Change of use
There are 2 ways of proving compliance;
a)
All new thermal elements being provided must meet the required standard for extensions.
If thermal elements are renovated (>25% surface area), then they must be up-graded to an improved standard.

If thermal elements are to be retained, then they must be up-graded (including windows) to an improved standard.

Heating and lighting must also meet the minimum standards.


Or
b)
Ensure calculated CO2 emissions do not exceed those for the same building up-graded in accordance with the required standards as above.


Material Alteration
As for change of use


Controlled Services and fittings
Must be installed to minimum standards, but generally specialists will need to be employed to prove this has been achieved.

Continuity of insulation

A Report must be submitted by a suitably qualified person confirming that suitable detailing and workmanship has been adopted.


Providing information
A Building Log-Book must be provided for the owner on completion of the works.



Page last updated on: 20/09/2010