Planning, building and the environment

Assessment methodology and software

Energy Performance Certificates and Display Energy Certificates have to be produced using the relevant calculation tool specified in the National Calculation Methodology. This applies for all energy certificates whether on construction, sale or rent, or for public display.

A number of different methodologies have been developed (or are in the process of being developed) for different types of building and building condition. A summary is provided below:

Energy Performance Certificate

Home on completion of construction:
SAP
Building not intended as a home on completion of construction:
SBEM or DSM
A home being sold or rented out:
RDSAP (unless the unusual nature of the building indicates that a more accurate assessment could be obtained using the SAP methodology)
A building catering for mixed use (i.e. combining dwelling and non-dwelling) is constructed, sold or rented out:
It should be treated as a single dwelling as described above if the commercial part can be converted back to residential use and there is common access i.e. each part does not have a separate access(for example, where within a house a portion has been separated out as a workshop, office, or surgery);
For other scenarios, treat the dwelling and non-dwelling parts separately using the most appropriate methodology for each element. For example, where a building contains both flats and offices use SAP or RDSAP for the flat and SBEM or DSM for the offices
For all other buildings being constructed, sold or rented out:
SBEM or DSM

Display Energy Certificate

Operational Rating Methodology - more information on ORCalc software tests can be found at the Building Energy Calculation Software Approval Scheme website (external link)

The methodologies explained:

SAP - Standard Assessment Procedure

SAP is the Government's Standard Assessment Procedure for energy assessments of dwellings. The current version of SAP, SAP 2005 (external link), has been adopted by Government as part of the England and Wales national methodology for calculation of the energy performance of buildings. It is used to demonstrate compliance for dwellings with Part L of the Building Regulations 2000 (in England and Wales).

SBEM - Simplified Building Energy Model

SBEM is a computer program developed by BRE that provides an analysis of a building's energy consumption. The SBEM tool (external link) is designed to cover buildings that are not dwellings. It has been adopted by government as part of the UK national methodology for calculation of the energy performance of buildings. It is used to demonstrate compliance for dwellings with Part L of the Building Regulations 2000 (in England and Wales).

Operational Rating Methodology

The methodology for the calculation of the operational ratings for display energy certificates is available below.

RdSAP - Reduced Data Standard Assessment Procedure

RdSAP is the new Government-approved standardised assessment procedure for energy assesments of existing dwelling. A full SAP assessment requires many data items that cannot be seen in a survey (or take too long to collect). RdSAP is an industry-agreed standard set of data items and a standard way of inferring the missing data.

DSM - Dynamic Simulation Model

A Dynamic Simulation Model is a software tool that models energy inputs and outputs for different types of building over time. In certain situations, SBEM, will not be sophisticated enough to provide an accurate assessment of a building's energy efficiency. In these cases Government-approved proprietary dynamic simulation models may be used. Communities and Local Government will provide such an approval.