Display Energy Certificates (DECs) show the actual energy usage of a public building (the Operational Rating) and allow the public to see the energy efficiency of a building. This is based on the energy consumption of the building as recorded by gas, electricity and other meters. The DEC should be displayed at all times in a prominent place clearly visible to the public.

Do all buildings require a DEC?

DECs are only required for buildings that have a total useful floor area of more than 500m2  (floor area will be reduced to 250m2 on 9 July 2015) that are occupied by a public authority or an institution providing a public service to a large number of people, and are frequently visited by members of the public. DECs are valid for one year. The accompanying Advisory Report is valid for 7 years.

To view the register or to check the validity of an DEC, please visit the Register.

Advice and guides on DECs for public buildings

The requirement to obtain and display a DEC came into effect on 30 December 2008.

Where a building is partly occupied by a public authority or a relevant institution, the authority or institution is responsible for displaying a DEC and having a valid Advisory Report. Other private organisations occupying the building, irrespective of the size they occupy, do not need to display a DEC.

A Guide to Display Energy Certificates (DEC)

Example of a DEC

Advice and guides for unmetered and campus DECs

Although multiple small buildings on a campus where each building is less than 500m2 are excluded, if these buildings are linked to one another by a heated space or are served by the same heating or cooling system then a DEC is required. The energy consumption for each separate building will then be derived by proportioning on the basis of floor area.

Important information on unmetered and campus DECs

Site based DECs are not acceptable in Northern Ireland.

Every building for which a DEC is required must display its own individual DEC. Where metering is at site level the DEC must be based on the metered site energy demands but with the consumption apportioned to each individual building on an area weighted basis. Where different benchmarks apply to the buildings on the site, for example a school building and a swimming pool building, then the relevant benchmark category for the building should be selected.

Subsequent to December 2009 it is expected that sub-meters have been installed where required.

How do I get a DEC?

An Energy Assessor, accredited to produce DECs for that type of building, is the only person who can produce a DEC and Advisory Report for your building.

To search for an accredited assessor and/or to check your assessor's credentials visit the epc register

The fuel and energy consumption data you provide will be reviewed by the assessor in line with the approved method. Adjustments may be made for occupancy, intensity of use, special energy uses, weather and climate.

For the purposes of the DEC the carbon dioxide emissions are based on the energy consumption and total useful floor area and building type, giving a measured CO2 emissions per square metre.

The assessor will use the approved calculation methodology to produce a DEC and an Advisory Report. The DEC will need to be lodged in a national register by the assessor and given a unique reference number.

What does a DEC contain?

A DEC must contain the following information:

  • the operational rating (the building as used) and the asset rating (the building as built - if available) as determined by the government approved method
  • the operational ratings and CO2 emissions for the previous two years and
  • a reference value such as a current legal standard or benchmark.

The operational rating is not required where an occupier has been in occupation for less than 15 months. The asset rating is not required in the DEC where an occupier entered into occupation of the building before 31st December 2008.

The DEC will also show the unique certificate reference number, the address of the building, the total useful floor area of the building, the name of the energy assessor, their employer (or trading name if self employed), the name of their accreditation scheme and the date when the DEC was issued.

DEC questions and answers

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