Why the building type changes the assessment
Every non-domestic building is assessed under the same regulations, but not with the same method, and the building type is what decides which applies.
Most premises are modelled with the Simplified Building Energy Model. SBEM Level 3 covers smaller, simple buildings with straightforward services – a shop, a cafe, a single office suite, broadly under 250 sqm. SBEM Level 4 covers larger buildings, anything with air conditioning, mechanical ventilation or several heating and cooling systems, and all new-build commercial work regardless of how simple it looks. The most complex buildings – those with atria, automated blind control or advanced HVAC strategies that SBEM cannot model reliably – need Dynamic Simulation Modelling at Level 5.
That distinction matters commercially, because moving from Level 3 to Level 4 typically changes the fee more than doubling the floor area does. It also explains results that surprise owners: a large, sparsely serviced warehouse can rate better than a small, heavily serviced office, because the certificate reflects the building fabric and its fixed services rather than how hard the space is worked. Process and plug loads – machinery, tills, computers, cooking equipment – sit outside the calculation entirely.
The pages below set out how each building type is assessed, what tends to drag its rating down, and which improvements move it most cheaply.
