What is SBEM?

The Simplified Building Energy Model (SBEM) is both a calculation methodology and a software module; it is provided by the UK Government as one of the approved ways of generating Energy Performance Certificates (EPCs) for non-domestic buildings. It is also an approved way of demonstrating compliance with the requirements of Part L of the Building Regulations in England & Wales (and equivalent legislation in other parts of the UK and the Republic of Ireland). SBEM is provided with a simple interface, iSBEM. Carbon Checker is also an approved interface to SBEM, so is an alternative to the iSBEM interface.

Too many zones for SBEM?

We have noticed that larger buildings are starting to be put through SBEM. Unfortunately, this has led to problems for some people as the Government’s SBEM engine seems to struggle when the number of zones in a building is more than about 200. There doesn’t seem to be an absolute cut-off point though, so some buildings with substantially more than 200 zones have worked. It seems that the issue might be as much to do with the number of surfaces as the number of zones. The limitations will apply to any interface to the SBEM engine.

We suggest that people who are hoping to run SBEM on buildings with more than about 200 zones seek advice from their accreditation scheme at an early stage. One strategy to avoid potential problems is to consider carefully whether zones can be combined to reduce the number of zones and surfaces being passed to SBEM. (This must, of course, be done in a way that’s consistent with SBEM’s zoning rules.)