UK Building Regulations compliance and Energy Performance Certificate (EPC) creation must be undertaken using the relevant calculation tool specified in the National Calculation Methodology (NCM). For non-dwellings you have a choice of using either:
- SBEM (Simplified Building Energy Model) tools
- DSM (Dynamic Simulation Model) tools
SBEM
SBEM is a compliance procedure/computer program developed by BRE that provides an analysis of a building's energy consumption for compliance. It 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.
A free, basic interface, iSBEM, is available from the Government or a variety of 3rd party commercial interfaces are on the market. IES offers one of only a few 3D model based interfaces to SBEM; it is integrated with our DSM tool.
In certain situations SBEM is not be sophisticated enough to provide an accurate assessment of a building's energy efficiency. In these, and in fact all situations, it is acceptable to use DSM as an alternative.
DSM
DSM uses dynamic thermal simulation modelling that complies with the NCM in order to show compliance. It uses real site weather data and simulates at hourly intervals throughout the entire year. The IES <Virtual Environment> powered by its Apache engine is one of only two approved DSM software tools.
By analysing the energy performance at hourly intervals as opposed to the monthly average calculated by SBEM, the results of DSM analysis are commonly more accurate and allow the modelling of buildings which have sophisticated features that vary non-linearly, such as:
- Night ventilation strategies
- Ventilation with enhanced thermal coupling to structure
- Demand-controlled ventilation
- Automatic blind control
- Variable speed pumping
- Light transfer between highly glazed internal spaces such as atria or light wells
Both SBEM and DSM are compliance procedures and due to the standardisation of data specified in the NCM, are not true representations of the energy consumption of your real building. It is prudent to use appropriate modelling tools for design purposes.
As IES’ SBEM and DSM compliance modules link to its full <Virtual Environment> suite of performance simulation tools, modelling for design can be carried out from the same 3D model allowing you to compare and contrast how meeting compliance criteria actually affects the building’s performance.
THE LEVELS
Energy Assessors in England & Wales and N. Ireland can only lodge EPCs within their accreditation banding, which can be at one or several levels depending on their experience on the different calculation tools:
Level 3 can undertake energy inspections of existing simple non-dwellings with frequently occurring characteristics using the SBEM method.
Level 4 can undertake energy inspections of new-build and existing simple non-dwellings using the SBEM method.
Level 5 can undertake energy inspections of any new-build and existing non-dwellings using the DSM method.
If you are qualified at Level 4 you are automatically qualified at Level 3. However, being competent at Level 5 does not make you competent at Levels 3 and 4.
