Approved document L

[edit] Introduction

The Building Regulations set out requirements for specific aspects of building design and construction. Regulation 26 of the building regulations states that “Where a building is erected, it shall not exceed the target CO2 emission rate for the building…”, and Schedule 1 – Part L Conservation of fuel and power states that provision for conservation of fuel and power shall be made by: limiting heat gain and losses and providing building service which are efficient, have effective controls and are properly commissioned and that information is provided so that the building can be operated efficiently.

There are four parts to Approved Document L:

Key criterion described in Approved Document L include:

The designed carbon emission rate (Dwelling Emission Rate (DER) for self-contained dwellings and individual flats (excluding common areas) and Building Emission Rate (BER) for buildings other than dwellings) must not exceed the Target Emission Rate (TER) for a notional building of similar type, size and shape. Both are expressed in kgCO2/m2 per year.
Fixed building services should achieve a reasonable standard of energy efficiency. This is intended to prevent inappropriate trade-offs between different elements of the building. Minimum limiting parameters are set for key components of the building fabric to ensure that this is the case.
Solar gains should be limited.
As-built performance should be consistent with the DER. This includes air-permeability testing and appropriate commissioning of building services systems.
Provision should be made for energy efficient operation by providing the building owner with information enabling them to operate the building in a way that uses no more fuel and power than is reasonable. This might be done by the preparation of a building log book.
Limiting fabric parameters.

Before construction begins, a design stage calculation must be issued to the Building Control Body (BCB), setting out the TER, BER or DER and the specification for the building.

Within 5 days of the completion of the construction, a report must be issued to the BCB setting out the TER, BER or DER, any changes that have been made to the specification, and an energy performance certificate (EPC). These calculations require that an air-permeability test is carried out to ensure that the building envelope has been constructed to a suitably high level of workmanship so that air (and so heat) will not 'leak' through the building fabric. In addition, the BCB is likely to require a commissioning notice.

For buildings other than dwellings, the TER and BER can be calculated and the EPC produced by following the National Calculation Method (NCM). This can be done by using approved simulation software (Approved Dynamic Simulation Models (DSMs)) or by using the Simplified Building Energy Model (SBEM), a 'simplified' compliance tool developed by BRE, which has a user interface called iSBEM.

For dwellings, the Standard Assessment Procedure (SAP) should be followed. This can be done by using a computer program approved for SAP calculations by BRE on behalf of the government.