Skip to content
The content on this page has yet to be rewritten for GOV.WALES. It is still correct and up-to-date.

Part L of the Building Regulations (Conservation of fuel and power)

The content of this page is not being updated. Get up to date information on Building regulations guidance at

Related Links

These Approved Documents have been amended because of the introduction of the revised Approved Document supporting regulation 7 (Materials and Workmanship).
Practice guidance for local planning authorities and developers on planning for sustainable buildings.
Tell us if you want any of the documents on this page in an alternative format.
Technical guidance on Part L of Schedule 1 of the Building Regulations 2010 – Conservation of Fuel and Power.

2014 changes (from 31 July 2014)

We have announced changes to Part L that come into effect from 31 July 2014, and have published new guidance documents for Wales:

Part L 2014 Calculation Software (from 31 July 2014)

Domestic Software

Carbon dioxide emissions and energy ratings for dwellings are calculated using the UK Government's Standard Assessment Procedure for the Energy Rating of Dwellings (SAP). The Building Research Establishment (BRE) lists SAP software approved for use in Wales.

SAP 2012 has been revised to support the 2014 amendment to Part L of the Building Regulations in Wales, which is expected to deliver an aggregate 8% improvement in new dwelling performance. SAP 2012 can be used for building regulations compliance purposes from 31 July 2014. For information on current approved SAP 2012 software, as well as the updated SAP 2012 guidance document, please visit the BRE website (external link).

Non-Domestic Software

The methodology for non-domestic buildings in the UK is the National Calculation Methodology (NCM). The procedure for demonstrating compliance with the building regulations for non-domestic buildings is by calculating the annual carbon dioxide emissions and primary energy consumption for the proposed building and comparing them with those of a 'notional' building which has the same size and shape. The NCM allows the calculation to be carried out either by the SBEM (Simplified Building Energy Model) or by approved simulation software tools.


SBEM has a basic user interface, iSBEM, which is a free tool. iSBEM is updated to reflect amendments in Part L of the Building Regulations or improvements to the tool functionality. The latest version which is suitable for use in Wales from 31 July 2014 is iSBEM v5.2.d and  can be  downloaded on the BRE website (external link).

FI-SBEM and Dynamic Simulation Modelling (DSM)

There are also commercial front-end software tools that interface with the SBEM engine and calculate the building carbon dioxide and energy performance. Dynamic Simulation Modelling (DSM) primarily applies to building analysis software that can model the thermal dynamic response of buildings. These software tools can be used to demonstrate compliance with regulations 25, 25C(a), 26, 26A, 27 and 27A of the Building Regulations in Wales.

The list of approved software for non domestic buildings in Wales from the 31 July 2014 can be found in the document below.

Archived versions of Approved Document L are available on the National Archives (external link).