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When does a refurbishment or extension need a new commercial EPC?

Updated 19 October 2026 · SEO Dons Editorial

Most refurbishments and extensions do not, on their own, require a new commercial EPC. The legal trigger from building work is narrow: the work has to change the number of separately used parts of the building and add or extend heating, hot water, air conditioning or mechanical ventilation. Otherwise the next certificate is due at the next sale or letting. There can still be good reasons to commission one sooner, and one good reason to think before you do.

What building work legally requires a new EPC?

Gov.uk lists three situations in which you must have an EPC: you rent out or sell the premises, a building under construction is finished, or there are changes to the number of parts used for separate occupation that involve providing or extending fixed heating, air conditioning or mechanical ventilation. The sale and letting triggers are covered in our guide to whether you need a commercial EPC; this page deals with building work.

The third is the one that catches refurbishment projects. Regulation 7A of the Energy Performance of Buildings Regulations 2012 applies where a building is modified so that it has a greater or lesser number of parts designed or altered for separate use than it previously had, and the modification includes providing or extending fixed services for heating, hot water, air conditioning or mechanical ventilation. Splitting a hypothetical single-let warehouse into three separately heated units, or merging two office suites into one with the heating extended across both, would both qualify.

When it applies, the person carrying out the building work must give the EPC to the owner and give notice to the local authority, including the certificate's register reference number, no later than five days after the work is completed. In England, where a registered building control approver is supervising the work, that notice goes to the approver instead. Building control has to be satisfied about this before it gives a completion certificate, so a missing EPC can hold up sign-off.

Does a refit or a new heating system need a new EPC?

No, not by itself. Government guidance on non-domestic EPCs says an internal refit with new heating, hot water, air conditioning or mechanical ventilation would not trigger the requirement unless the building were also converted into more or fewer parts for separate use. Its worked example is blunt: a complete internal refit with new services and no parts added or removed means no EPC is required.

That does not mean the work escapes regulation. Gov.uk notes that many alteration projects may need building regulations approval, including installing or replacing a heating system, putting in fixed air conditioning, and replacing windows and doors. The EPC rules and the building regulations are separate regimes, and a project can be caught by one without the other. If the refurbishment also changes how the building is used, see our guide to EPCs and change of use.

What about extensions?

The guidance takes the same approach. A building that has been extended without adding or removing a separate part does not need an EPC, although the work may need to comply with building regulations. A building extended with a new separate part, served by new heating, ventilation, air conditioning or hot water, does need one.

Extensions also carry Part L consequences. Approved Document L Volume 2 says a large extension should be regarded as a new building for energy purposes, where its floor area is greater than 100 square metres and greater than 25% of the existing building's total useful floor area. Smaller extensions follow the guidance for new elements in existing buildings.

What does Part L expect from work on an existing building?

At a high level, Part L standards attach to the building work being carried out. Building work includes extensions and the provision or extension of a controlled service or fitting. Three points matter most for commercial owners.

  • Thermal elements. Under regulation 23, renovating more than 50% of a wall, floor or roof's surface means the whole element must meet the Part L standard, in so far as that is technically, functionally and economically feasible.
  • Consequential improvements in England. For existing buildings over 1,000 square metres, an extension, the first provision of fixed building services or an increase in their installed capacity can require additional energy efficiency work. For an extension, Approved Document L says the value of those improvements should not be less than 10% of the value of the principal works.
  • Wales is different. The Welsh version of regulation 28 applies consequential improvements to any existing building that is extended, with no floor area threshold.

Revised Part L standards come into force in England on 24 March 2027, with transitional protection for work notified before that date and started before 24 March 2028. Wales has its own revised Volume 2, taking effect on 4 March 2027. You can use either your local authority's building control service or a private registered building control approver.

Can a new EPC help or hurt your MEES position?

For a let building, the rating matters because of the minimum energy efficiency standard. Since 1 April 2018 a new non-domestic tenancy has needed at least an EPC E rating unless an exemption is registered, and from 1 April 2023 that applies to all privately rented non-domestic property, even without a change in tenancy. Government guidance adds that a let property marketed or modified in the past 10 years will probably be legally required to have an EPC. Our MEES compliance page covers the detail.

How it helps. If works have lifted the building's performance, a new certificate is how that improvement gets recorded. For an F or G rated building, our guide to improvement options for F and G ratings sets out what usually moves the score.

How it can hurt. The most recent EPC is the valid one, and once a certificate is registered it cannot be altered. A fresh assessment is also calculated with the methodology and software approved at the time: the notice of approval dated 24 March 2026 superseded the June 2025 version, and approved software is revised from time to time. So a new rating will not necessarily match the old one, even where little has changed. If the purpose is MEES, plan the works first and commission the certificate when they are finished, rather than lodging one mid-project.

When is it worth commissioning a new EPC anyway?

Government guidance says that where accommodation has been renovated, for example with upgraded heating or a change of use, it would be preferable to have an updated EPC, even though one is not required. An up-to-date certificate also gives buyers and tenants an accurate picture, and its recommendation report reflects the building as it now is.

Otherwise, timing follows the transaction. An EPC is valid for 10 years and can be reused within that period, but if no valid certificate exists when you decide to sell or let, one must be commissioned before the building is put on the market. If you are unsure whether that point has arrived, check the EPC triggers first. When one applies, you can request quotes from accredited assessors through the form on this site.

Sources

Common questions

Does replacing the boiler mean we need a new EPC?

Not on its own. Government guidance says new heating, hot water, air conditioning or ventilation does not trigger an EPC unless the building is also converted into more or fewer separately used parts. The replacement may still need building regulations approval.

Who has to provide the EPC after qualifying building work, and when?

The person carrying out the building work must give the EPC to the owner and give notice, with the register reference number, to the local authority or, in England, to the registered building control approver supervising the job. Both are due no later than five days after the work is completed.

Will a new EPC replace our existing one even if the rating is worse?

Yes. The most recent EPC is the valid one, and registered certificates cannot be altered. That is why it pays to finish planned improvements before commissioning a new certificate.

Do consequential improvements apply to every extension?

In England they apply to existing buildings over 1,000 square metres that are extended or gain new or larger fixed building services. In Wales, regulation 28 applies them to any extension of an existing building.

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