Introduction to NCM
The National Calculation Method for the EPBD (Energy Performance of Buildings Directive) is defined by the Department for Communities and Local Government (DCLG). The procedure for demonstrating compliance with the Building Regulations for buildings other than dwellings is by calculating the annual energy use for a proposed building and comparing it with the energy use of a comparable 'notional' building. Both calculations make use of standard sets of data for different activity areas and call on common databases of construction and service elements. A similar process is used to produce a 'asset rating' in accordance with the EPBD. The NCM therefore comprises the underlying method plus the standard data sets.
The NCM allows the actual calculation to be carried out either by an approved simulation software or by a simplified tool based on a set of CEN standards. That tool has been developed for DCLG by BRE and is called SBEM - Simplified Building Energy Model. It is accompanied by a basic user interface - iSBEM.
Introduction to SBEM
SBEM is a computer program that provides an analysis of a building's energy consumption. SBEM calculates monthly energy use and carbon dioxide emissions of a building given a description of the building geometry, construction, use and HVAC and lighting equipment. It was originally based on the Dutch methodology NEN 2916:1998 (Energy Performance of Non-Residential Buildings) and has since been modified to comply with current CEN Standards. Details of the calculation method, the algorithms used and the assumptions made are provided in the SBEM Technical Manual, available from the Download page.
SBEM makes use of standard data contained on associated databases and available with other software.
The purpose of SBEM and its interface iSBEM is to produce consistent and reliable evaluations of energy use in non-domestic buildings for Building Regulations Compliance and for Building Energy Performance Certification purposes. Although it may assist the design process, it is not primarily a design tool. It does not calculate internal temperatures, for example.
As iSBEM is a compliance procedure and not a design tool, if the performance of a particular feature is critical to the design, even if it can be represented in SBEM, it is prudent to use the most appropriate modelling tool for design purposes. In any case, SBEM should not be used for system sizing.
In line with revisions to Approved Document ADL2A, SBEM and iSBEM have been revised and updated a number of times to include additional functionality. The current version - v5.2.d - can be used for demonstrating compliance with Part L 2013 in England and for generating Energy Performance Certificates. It can also be used for Building Regulations and EPCs in Wales. See the Download pages for more details of applicability in different parts of the UK and the Republic of Ireland. The tool, along with a user guide, can be downloaded free of charge from the Download pages.
SAP for dwellings
The calculation method for dwellings under Part L 2013 is a new version of SAP - the Standard Assessment Procedure for the Energy Rating of Dwellings. This is specified in documents available at http://www.bre.co.uk/sap2012/ and is implemented through a number of commercially available software tools.
ORCalc Methodology (for Display Energy Certificates)
The purpose of Display Energy Certificates (DECs) is to raise public awareness of energy use and to inform visitors to public buildings about the energy use of a building. DECs provide an energy rating of the building from A to G, where A is very efficient and G is the least efficient, based on the actual amount of metered energy used by the building over a 12 month period.
For further information regarding DEC’s and the ORCalc please visit