An early SBEM calculation shows the proposed non-domestic building outside its applicable Part L target. The useful response is not to change a number in the model until it passes. First establish whether the inputs match the design; then compare realistic design options with the architect and building-services team. The calculation becomes valuable when it helps decisions while those decisions can still be made.
Check the model before changing the building
Confirm the drawing revision, floor areas, orientation, zoning and each room's activity. Compare entered U-values, glazing performance and air-permeability assumption with the actual specification. Missing plant efficiencies or generic lighting inputs can distort the picture. SBEM is an approved modelling route for suitable non-domestic buildings, but the correct software version and regulatory edition depend on the project. Ask the assessor to explain the inputs and the reported shortfall in plain terms.
Test changes as a coordinated package
Improved fabric can reduce heat demand, but glazing, shading and daylight affect cooling and lighting as well. Efficient heating or ventilation equipment may matter less if controls and operating zones are poorly described. Review fixed lighting power, control strategy, heat recovery and the proposed low-carbon or renewable systems with the designers. Model a few buildable combinations, recording the effect on the relevant metrics, cost and construction programme. No single technology guarantees compliance.
Keep evidence aligned with what gets built
A promising design-stage result can be lost when glazing, plant or lighting changes during procurement. Keep an agreed schedule of performance specifications and notify the assessor when substitutions are proposed. At completion, the as-built calculation must reflect the actual building and the applicable Part L submission route. The building control body assesses the evidence; a modelling report is not approval by itself.
Use the shortfall to decide the next move
Ask for a concise list of the strongest design levers, the assumptions that need confirmation and the documents still missing. This turns an SBEM result into a design conversation rather than a pass-or-fail surprise at handover. For complex geometry or systems, the assessor may need to discuss whether another approved modelling route is appropriate. Our SBEM Calculations service can review the project stage, drawings and proposed building services before the next model revision.