When Is a DEC Required for Public Buildings?

A Display Energy Certificate is not required simply because a building is large, publicly owned or used by a public-facing organisation. The key question is who occupies it and whether the public regularly visits. So, when is a DEC required? In England and Wales, it is generally required where a public authority occupies a building with a total useful floor area over 250m² and the building is frequently visited by the public.

That one is pretty simple in principle. In practice, mixed-use sites, shared offices and changing occupiers can make the answer less obvious. Getting it right matters because a DEC must be clearly displayed, is based on actual energy use and is designed to show the public how efficiently a building is being run.

When is a DEC required?

A DEC is mandatory when all three of the following apply:

• The building has a total useful floor area of more than 250m².

• It is occupied by a public authority, or by an institution providing public services to a large number of people.

• It is frequently visited by the public.

Examples often include council offices, libraries, schools, leisure centres, hospitals, GP surgeries, museums and other public service buildings. The rule is concerned with the occupied building or relevant part of a building, rather than the size of the wider site alone.

A public authority includes bodies carrying out functions of a public nature. However, not every organisation offering a public service will automatically fall within the requirement. The nature of the occupier, how the building is used and the level of public access all need to be considered.

For instance, a council-run library over 250m² will usually need a DEC because visitors routinely enter and use the building. A back-office building used only by council staff, with no regular public access, may not. Equally, a privately run gym may welcome the public every day, but this does not automatically make it subject to the DEC requirement. It may instead need a Commercial EPC in the relevant circumstances.

What does “frequently visited by the public” mean?

This part of the rule is often where uncertainty arises. Frequent public visits means more than occasional appointments, supplier deliveries or a reception that is rarely used. The building should be one that members of the public commonly enter as part of receiving a service.

A school is normally a straightforward example. Parents, pupils and visitors use it regularly, and it provides a public service. A local authority office with a customer-service counter is another. By contrast, a secure operations centre, storage depot or staff-only administrative office may have limited visitor access and may fall outside the requirement.

The assessment should reflect the building’s normal use, not one-off events. If public access is limited to an annual open day, that would not usually be enough. If access patterns change - for example, a former staff office becomes a public advice centre - the DEC position should be reviewed promptly.

The 250m² threshold and shared buildings

The 250m² figure refers to total useful floor area. This is the area within the building envelope that is intended to be heated, cooled or mechanically ventilated for occupants. It is not simply the footprint shown on a site plan.

For buildings with several occupiers, the answer depends on how the space is arranged and used. A public authority may occupy only part of a larger building. If that area operates as a distinct, frequently visited public building and exceeds the threshold, a DEC may be needed for that part. Where services and energy supplies are shared, the practical scope of the certificate needs careful consideration.

This is one reason a quick desk-based assumption can cause problems. A building may have one postal address but contain several separate areas with different occupiers, meters and opening arrangements. An experienced assessor can establish the most appropriate approach before the assessment takes place.

What a DEC measures

A Domestic or Commercial EPC estimates the energy performance of a building based on its construction, systems and assumed use. A DEC works differently. It shows the actual energy used by a building over a 12-month period, taking account of factors such as weather.

The certificate gives an operational rating from A to G. A lower number indicates better energy performance, while the rating helps visitors and building managers see how actual consumption compares with a typical building of the same type.

This difference is useful. A well-insulated building can still have a poor DEC rating if heating controls are poorly managed, equipment is left running or occupancy patterns have changed. Likewise, a building with older fabric may perform reasonably well if it is carefully operated.

A DEC therefore is not just a compliance document. It can highlight where energy bills, carbon emissions and day-to-day building management deserve closer attention.

How often does a DEC need renewing?

The renewal period depends on the size of the building. For a public building with a total useful floor area over 1,000m², the DEC is valid for one year. For qualifying public buildings between 250m² and 1,000m², the DEC is valid for two years.

An accompanying advisory report is valid for seven years. The report sets out recommendations for improving the building’s energy performance. Even where an existing report remains valid, the DEC itself must still be renewed at the correct interval.

Because the certificate is based on actual annual energy consumption, it is sensible to plan ahead. Electricity and gas data needs to cover the relevant period, and gaps in meter records can slow down the process. If a site has changed meter, fuel type, occupancy or operating hours, flag this early so the assessor can advise on the information required.

Where must the certificate be displayed?

A valid DEC should be displayed in a clearly visible place where it can be easily seen by members of the public. A reception area, main entrance or public noticeboard is often suitable, provided visitors can see it without needing permission to enter a secure area.

Keeping a current certificate in a facilities file is not enough. The requirement is to display it. Building managers should also make sure an out-of-date DEC is removed or replaced as soon as the new one is issued.

There can be financial penalties for failing to obtain, display or make available a required DEC. More importantly, a missed certificate can create avoidable pressure for facilities teams and public-sector property managers who are already balancing compliance, budgets and operational demands.

When a DEC is not required

Many buildings do not need a DEC, even if they are busy or energy intensive. Private commercial premises, for example, are not normally required to display a DEC solely because customers visit them. They may require a Commercial EPC when constructed, sold or let, but that is a separate requirement.

Smaller public buildings of 250m² or below are also outside the usual mandatory DEC threshold. Buildings that are not frequently visited by the public may be outside scope as well, although each case should be considered on its facts.

There are also situations where a building may be exempt from EPC-related requirements because of its nature, such as certain temporary buildings, places of worship or buildings due for demolition. Exemptions are specific and should not be assumed to apply to a DEC without checking the current rules and the building’s use.

A practical way to stay compliant

For portfolio managers, the simplest approach is to maintain a register of public buildings, their floor areas, occupiers, public-access arrangements and DEC expiry dates. Record when the advisory report expires too. This gives teams time to gather 12 months of energy information and arrange the assessment before compliance becomes urgent.

It also helps to review the register when services move, buildings are altered or a lease changes. A previously exempt office can become a public-facing building, while a public counter closing to visitors can change the position in the other direction.

Kings Energy Hub provides DEC assessments for qualifying public buildings across the East Midlands and surrounding areas, with clear advice on the information needed before the visit. If you are unsure whether a particular school, library, surgery or office falls within the rules, checking before the deadline is usually quicker and far less troublesome than correcting a missed requirement later.