Display Energy Certificates (DEC) for Large Public Buildings

From the 9th January 2013, publicly and privately owned large buildings, as defined in S.I. 243 of 2012, frequently visited by the public, are required to exhibit a DEC, in a prominent place, clearly visible to the public. The DEC is intended to encourage public authorities to adopt environmentally responsible and efficient use of energy in buildings.


What is the definition of a public body?

The definition of a public body is contained in S.I. No. 243 of 2012. It includes any public body or public authority/ institution set up by Government enactment. The Dept of State, Local Authorities, HSE and public educational establishments..

What is the format of the DEC?

The DEC is based on the measured energy use, where the actual energy consumed in the building is compared to a benchmark for similar buildings, and shown on the certificate A1 - G scale in terms of primary energy. There is also a CO2 indicator which shows the CO2 emissions associated with the building's energy consumption. Benchmark or typical buildings have a E1 rating. The DEC layout is specified in S.I. 243 of 2012.

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How is a DEC calculated?

The DEC rating is calculated on the basis of the ACTUAL energy consumption, during occupation, over a ONE YEAR period. The DEC reflects the use of the building and the practices of management and maintenance. This is calculated from meter readings/ bills or an alternative reliable source. From this, an operational rating is derived. The energy used by the building over the year is required. This may include gas fuels, oil fuels, solid fuels, district heating and cooling and electricity. Energy consumption is ideally obtained directly from onsite incoming energy meters, or from energy supply company bills. If this information is not available from those maintaining the building or the landlord, an estimate should be provided from the energy supplier. The Assessor can only use estimates data directly from the energy supplier and no other source

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How do you calculate a DEC for campus facilities?

Many campus style facilities have metering at the site level rather than at the building level. In such cases, the DEC should be based on the metered site energy demands, and the energy used by each building would be determined from the site energy consumption on a simple area weighted basis. A DEC should be displayed for each qualifying large building, as defined in S.I. 243 of 2012.


Ireland has adapted the methodology, developed in the UK, for the purposes of generating the DEC. The benchmarks are adjusted to take local factors into consideration. Additional software has been developed to aid the calculation procedure. The set of benchmarks relate to specific building use categories with standard use patterns and are made for specific locations and climate. Provisions are made for the following:

  • Where the actual building usuage covers more than one of the chosen building use categories . This composite benchmark is derived on a pro rata basis, taking account of the floor area applicable to each identified use.
  • Where there is significant climate differences between the location of the building being assessed and that assumed in the standard benchmark.
  • Where the use periods of the builidng are significantly greater than those assumed in the standard benchmark, up to a set limit of extended use.
  • Energy used for specific identified processes, may be excluded in exceptional circumstances. As part of the benchmarking process, CIBSE has identified activities that can be considered as significantly more intensive in their use of energy relative to those usually found in a particular building use category. Where these occur, both the energy use and floor area associated with the particular activities can be ommited from the assessment, provided that the separable energy uses are separately metered.

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When is the exhibition of a Display Energy Certificate (DEC) legally required?

From 9th July 2015 a DEC is required for:

- Buildings occupied by a public body with a total useful floor area in excess of 250m2, and frequently visited by the public

- Buildings (other than occupied by a public body) with a total useful floor area in excess of 500m2 and frequently visited by the public

Are any buildings exempt from the requirement for a DEC?

Exempted categories of buildings are listed in S.I. 243 of 2012. However SEAI encourages public bodies to generate and display a DEC for all buildings.

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Does the DEC relate to a whole building or to the part of a building?

The DEC requirement relates to any building or part of a building that satisfies the definition of a large building, as specified in S.I. 243 of 2012.

How soon after occupation can a DEC Assessment be carried out?

A DEC can be carried out at any time. If the building has just been occupied and therefore there is not sufficient billing data available, the response to the question - 'Do you have metered, estimated or apportioned measurements of energy consumption to cover more than 95% of all the energy used by the building? is 'No' resulting in a 'G' grade energy rating.

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What happens if there is not a sufficient amount of data?

If there isn't sufficient billing data available, the rating will default to G.The data has to be metered or an estimated measurements of energy consumption to cover more than 95% of energy used by the building.

Who can carry out a DEC Assessment?

DECs are completed by DEC Assessors registered with SEAI. Candidates seeking to register as a DEC Assessor must be registered with SEAI as a Non-Domestic BER Assessor and successfully complete a DEC Assessor workshop delivered by SEAI

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How is the DEC generated?

The DEC procedure involves the collection of all relevant data required to produce the certificate by the registered DEC Assessor. The data is entered ih an online tool and the DEC is generated by SEAI. Once the relevant party receives the DEC, it must be displayed in a prominent place. The certificate displays the grade awarded, an energy performance indicator, a CO2 performance indicator, histograms of trends in energy, primary electrical and heating energy per unit, a building identifier, basic building technical information, period of validity of the DEC, a unique DEC number and DEC Assessor number.

Where should the public body display the DEC?

In addition to the hard copy on display, public bodies may wish to provide a valid cert via a website or other publicly accessible media, show the full technical data that gives underlying details on the building and its energy performance and display supplementary information to explain the contents of the certificate, including any reasons explaining poorer/ better performance to the previous years result.

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How does a DEC differ from the BER (Building Energy Rating), that is required at construction, sale or rent of a building?

Building Energy Rating (BER) rating for domestic and non-domestic buildings is a rating certificate based on calculated energy use.
Display Energy Certificate (DEC) rating is a rating certificate based on measured energy use.

Do private buildings for sale or rent require a DEC?

The requirement for a DEC for privately and publicly owned buildings is in addition to the requirement for a BER.


Technical Bulletin for Large Public Buildings

Public buildings technical bulletin Dec 09.pdf (size 259.7 KB)
Its content includes information on:

  • Non Metered energy use
  • Stock Levels
  • District heating co efficients
  • Metered energy use
  • Utility bills
  • Occupancy hours
  • Calculating floor areas

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