Note: This is a general guide for UK commercial property owners and professionals. Non-domestic EPC regulations, registers and processes differ across England & Wales, Scotland and Northern Ireland. Always check the current position on GOV.UK and the relevant national register before acting on any specific matter.
Level 3
Level 3 covers existing buildings with simple heating and ventilation — typically natural ventilation with straightforward heating, no comfort cooling and no complex controls. Most small shops, simple offices and basic industrial units sit here and are modelled in iSBEM.
Level 4
Level 4 covers existing buildings with more complex services: mechanical ventilation, comfort cooling, VAV or fan-coil systems, heat recovery and more sophisticated controls. It still uses iSBEM but requires an assessor accredited to the higher level.
Level 5 and dynamic simulation
Level 5 uses approved Dynamic Simulation Modelling software rather than iSBEM. It is needed where the building or its services fall outside what iSBEM can represent — atria, complex façades, unusual mixed-mode strategies, CHP, and many new-build Part L submissions.
Using the correct level matters: an assessment carried out at too low a level for the building can be challenged and may need to be redone.
Next steps
If you'd like specific advice about a property or portfolio, request a quote and our in-house assessors will come back to you.