New Build/Conversion Commercial EPC Assessment: Covering England and Wales

A New Build/Conversion Commercial EPC Assessment is the non-domestic EPC assessment used for a new commercial building or a commercial building created or materially modified by conversion. In practice, it is the route used for offices, retail units, industrial units, warehouses and other buildings other than dwellings when the EPC is linked to construction completion or qualifying modification, not a routine existing-premises sale or renewal EPC.

No. This service is for new-build commercial buildings and commercial buildings created or reconfigured through conversion or qualifying modification, not the ordinary EPC route for an existing office, shop, warehouse or industrial unit being re-let or sold in its existing form. If the premises is simply an existing non-domestic property on the market, that is a different EPC workflow.

Yes, where the end result is a building other than a dwelling and the project falls into the construction or qualifying-modification route. The non-domestic EPC guide also makes clear that a modified building requires an EPC where it ends up with more or fewer parts designed for separate occupation and the modification includes the provision or extension of fixed services such as heating, air conditioning or mechanical ventilation.

Yes, often it does. The official non-domestic EPC guide says that if a building is modified so it will have more or fewer parts designed to be used separately, and the modification includes the provision or extension of fixed services for heating, hot water, air conditioning or mechanical ventilation, an EPC is required when the work is complete. That is a classic trigger on subdivision and reconfiguration jobs.

The approved route is the National Calculation Methodology (NCM) for buildings other than dwellings, implemented through SBEM or an approved Dynamic Simulation Model (DSM). The 2026 England notice of approval says the energy performance of a building that is not a dwelling must be calculated using an approved implementation of the NCM, i.e. SBEM or an approved DSM, and the Welsh notice says the same for new buildings other than dwellings in Wales.

No. A commercial EPC is an asset rating based on the building’s calculated energy performance, while a DEC is an operational rating based on the actual energy consumption of certain public buildings. The official DEC guide says a DEC reflects actual metered use over the previous 12 months, whereas the approved methodology notice for EPCs describes the EPC route as an asset-rating calculation.

No. The EPC is part of the overall energy-performance package, but it is not the same thing as full Part L compliance evidence. For non-domestic new buildings, Approved Document L requires design-stage and as-built BRUKL reports, target and building primary energy and emission rates, plus supporting specification lists. The EPC matters, but it is not the only document Building Control relies on.

A BRUKL report is the Building Regulations UK Part L compliance report used to show energy-compliance evidence for a non-domestic building. Approved Document L in England says the BRUKL report should be provided to the Building Control body and to the building owner to show that the work complies with the energy-efficiency requirements, and that SBEM produces it as a standard output.

Yes. The official non-dwelling EPC guide says that where building units are let as bare structures without services, but there is an expectation they will be fitted out and energy will be used to condition the indoor climate, an EPC should still be provided. Approved Document L also has dedicated shell-and-core provisions for the design-stage and as-built Part L calculations.

Treat it as a live compliance workstream, not a final-day certificate request. The strongest route is to appoint the assessor at design stage, complete the BRUKL submission before works start, keep use-class and zoning assumptions stable, track substitutions carefully, and finalise the as-built information before Building Control is waiting on it. The legal handover duty is tied to physical completion, so late EPC work almost always becomes a programme issue.