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Can a Level 5 (DSM) EPC change your rating?

Updated 23 October 2026 · SEO Dons Editorial

When is a Level 5 (DSM) EPC required?

A building is Level 5 when a dynamic simulation model (DSM), not SBEM, is used to assess it. The government's guide says that in certain situations SBEM "may not be sophisticated enough to provide an accurate assessment of a building's energy efficiency", and that in these cases government-approved dynamic simulation models may be used.

Elmhurst Energy is one of the accreditation schemes the government's guide lists. Its guide to the levels names buildings with atria, automatic shading systems, extensive use of thermal mass or highly glazed facades as examples, and gives airports and large shopping centres as typical Level 5 buildings. It says such buildings "cannot be modelled reliably using simplified methods".

The NCM website, which hosts the official SBEM guidance, points to DSM in three specific situations:

  • Borrowed daylight. Where daylight passes to an internal zone, for example through glass partitions, and is a key design feature with a significant impact, the FAQ says you will need an approved DSM instead of SBEM.
  • An HVAC system SBEM does not offer. The FAQ says you might be able to use an approved DSM to model the building.
  • Tight humidity control. The FAQ says SBEM does not currently consider energy for humidification and dehumidification.

Elmhurst describes the assessor reviewing the building's size, use and services and then modelling its performance with the appropriate software. The certificate must be issued by an assessor accredited for that category of building, and Level 5 assessors are specifically trained and approved to use DSM software.

Can an owner choose DSM for a building that SBEM could model?

The approved method can be applied in either tool. The government's notice of approval says the energy performance of a building that is not a dwelling must be calculated using "an approved implementation of the National Calculation Methodology for buildings other than dwellings, i.e. SBEM or an approved DSM". The guidance, however, presents DSM as the route where SBEM falls short, not as an optional upgrade. Whether a given building should use it is for an assessor accredited at Level 5 to confirm after survey, and the SBEM Level 3 vs Level 4 vs DSM guide explains how the levels are set.

Can a DSM model give a different rating from SBEM for the same building?

Yes, because the two methods describe the building differently. SBEM "estimates the monthly energy use and carbon emissions of a building" from a description of its geometry, construction and services, using a fixed set of system options. A dynamic simulation model, in the guide's words, "models energy inputs and outputs for different types of building over time". Where an HVAC system is not among SBEM's options, the NCM website says it could be acceptable to select a substitute system to produce "approximate results". A DSM model can describe the system itself.

As a hypothetical illustration, take an office with a central atrium and automatic shading. Elmhurst lists both among the features that simplified methods cannot model reliably. A DSM model represents them in its own terms, so its inputs and calculation differ from an SBEM model's, and the two results need not match. None of the sources used for this page says which way a difference goes, because DSM exists to give an accurate assessment, not to favour a band.

What stays the same whichever method is used?

  • Standard assumptions. The NCM website says the parameters and schedules for each activity are standardised to allow consistent comparisons and cannot be modified by the user for energy certification. The assessor cannot tune them to reach a band.
  • Approved software. The notice of approval says a software tool must be validated against published criteria to operate consistently with the approved methodologies. That covers DSM tools as well as SBEM interfaces.
  • Verification. For level four and five buildings the assessor must visit, inspect and record where the data came from.
  • Duty of care. Energy assessors must carry out assessments with reasonable care and skill.
  • Recourse. If a result looks wrong, the route is the same as for any EPC. What to do if your commercial EPC looks wrong explains it.

The assessor models the building as it is. Choosing the method does not choose the outcome.

Why is this a MEES planning question for complex buildings?

Because MEES tests the valid EPC. A let property is sub-standard where its valid EPC expresses its performance as below band E, and an EPC is valid if it was entered on the register no more than 10 years before it is relied on and no other EPC for the property has since been entered. A new EPC, by either method, therefore replaces the old one whatever its band. The MEES compliance guide covers the rules and exemptions.

For the largest buildings there is a second test on the horizon. The government's interim response says that from 2031 it is proposed that all private rented buildings over 1,000 square metres in England and Wales will need to reach EPC B, where cost effective. The changes will only take effect following the successful passage of secondary legislation, and further detail on implementation of the threshold is still to come. The existing 7-year payback test and exemptions are to remain. EPC B by 2031 sets out what that means.

For a tall office, an atrium building or a shopping centre, three questions follow. Which level does the building require? What rating does an assessment at that level record? What does the recommendation report suggest to close the gap to E now, or to B if the proposal becomes law?

What does Level 5 add to the fee and the workload?

More detailed modelling and a more specialised assessor. A Level 5 building is modelled in DSM software by an assessor accredited at that level, and the assessor must visit, inspect and record the provenance of the data. Those requirements bear on the fee. Level 5 EPC cost: what drives the price of a DSM assessment sets out the drivers, and the commercial EPC cost guide shows how fees are built up at every level.

When does it make sense to ask about Level 5?

  • The building has features Elmhurst links to Level 5: atria, automatic shading, extensive thermal mass or a highly glazed facade.
  • An assessor tells you SBEM would rely on approximations for a significant feature, such as an HVAC system it does not offer.
  • The building is let, or soon will be, and is over 1,000 square metres, so a reliable baseline will matter for the proposed 2031 standard.
  • You are comparing quotes and want to be sure each assessor is pricing the same level, which the cost guide helps with.

It does not make sense as a way to shop for a different band. The guidance describes DSM as a route to an accurate assessment where SBEM falls short.

Sources

Common questions

Will a Level 5 assessment remove an F or G rating?

Not by itself. A new EPC replaces the earlier one for the building whatever its band, and the band is whatever the assessment records for the building as it is. If the building is let, MEES tests the valid EPC, so the practical routes to E are the improvements in the recommendation report or a registered exemption.

Can the assessor switch to DSM because I ask?

The approved method can be applied in SBEM or an approved DSM, and the guidance presents DSM as the route where SBEM may not be sophisticated enough. Which applies to your building is for an assessor accredited at the right level to confirm after survey.

What if I think a Level 5 result is wrong?

Complain to the assessor first. GOV.UK says that if you are still unhappy you can contact the assessor's accreditation scheme, whose details are on the certificate. Schemes must also provide for resolving complaints against their members.

Does the 1,000 square metre line in the 2031 proposal apply to the whole building or the let space?

The interim response refers to private rented buildings over 1,000 square metres and says further detail on implementation of the threshold will come in the forthcoming government response. Check that response before assuming either reading.

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