| Method | What it is | Typically used for |
|---|---|---|
| SBEM | The Simplified Building Energy Model – the national calculation engine, maintained by BRE | The great majority of commercial buildings |
| iSBEM | The interface an assessor uses to enter a building into SBEM | The data entry layer, not a different method |
| DSM | Dynamic Simulation Modelling – approved third-party software running an hourly simulation | Atria, mixed-mode ventilation, complex servicing, unusual geometry |
How the rating is produced
In outline: the assessor divides the building into zones by activity and servicing, describes the fabric and services of each, and the engine calculates the building's annual carbon emissions. That figure is compared with the emissions of a notional reference building of the same size and shape built to a defined standard. The ratio produces the asset rating, and the rating produces the band.
Two consequences follow, and both matter.
- The zoning is a judgement. How a building is divided affects the result. A building zoned coarsely by an assessor working quickly can be rated differently from the same building zoned carefully.
- The reference building moves with the methodology version. A certificate produced under an earlier version is not directly comparable with one produced today, which is part of why a re-assessment after ten years can surprise in either direction.
Reading the method off your certificate
The certificate records the calculation tool and version used, the assessor, their accreditation scheme, and the lodgement date. If you are comparing two certificates for the same building and cannot reconcile them, that block is usually where the answer is.
Find the certificate you already have
Search the Energy Performance of Buildings Register for your building. It is free, there is no sign-up, and it takes about ten seconds.
Common questions
What is SBEM?
The Simplified Building Energy Model – the calculation engine behind most non-domestic EPCs in the UK. Assessors enter the building through an interface called iSBEM.
What is a DSM assessment?
A Dynamic Simulation Model – approved software used for buildings SBEM cannot represent properly, such as atria, complex ventilation or unusual servicing strategies.
Does the assessment method change my rating?
It can. A complex building forced through SBEM may be penalised for features the simplified model cannot credit. Where that is suspected, a DSM assessment is the remedy.
Sources
- National Calculation Methodology and SBEM – uk-ncm.org.uk
- Approved Document L, Volume 2: buildings other than dwellings – GOV.UK
Legislation is cited to the version in force at the date below. We publish a corrections policy and amend pages when the law changes.