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What is DEC?

Source: ‘Improving the energy efficiency of our buildings - A guide to Display Energy Certificates and advisory reports for public buildings’ by Communities and Local Government

A Display Energy Certificate shows the energy performance of a building based on actual energy consumption as recorded annually over periods up to the last three years (the Operational Rating). The DEC also shows an Asset Rating for this building if this is available (by way of an EPC). A DEC is valid for one year and must be updated annually.

The Operational Rating (OR) is a numerical indicator of the actual annual carbon dioxide emissions from the building. This rating is shown on a scale from A to G, where A is the lowest CO2 emissions (best) and G is the highest CO2 emissions (worst). Also shown are the Operational Ratings for the previous two years; this provides information on whether the energy performance of the building is improving or not.

The OR is based on the amount of energy consumed during the occupation of the building over a period of 12 months from meter readings and is compared to a hypothetical building with performance equal to one typical of its type (the benchmark). Typical performance for that type of building would have an OR of 100. A building that resulted in zero CO2 emissions would have an OR of zero, and a building that resulted in twice the typical CO2 emissions would have an OR of 200. If the building is a net energy generator, it would still be given an Operational Rating of zero.

A DEC must be accompanied by an advisory report and the owner of the building must have a valid one available. The advisory report highlights recommendations to improve the energy performance of the building (i.e. its fabric and associated services such as heating, ventilation and lighting). An advisory report is valid for seven years.

What buildings require DEC and when?

A DEC and advisory report are required for buildings with a total useful floor area (see Glossary of terms for a definition) over 1000m2 that are occupied in whole or part by public authorities and by institutions providing public services to a large number of persons and therefore frequently visited by those persons.

Private organisations, including those that may share a building with a relevant institution, do not need to display a DEC, but may elect to do so on a voluntary basis.

Who should get a DEC?

It is the responsibility of every occupier of a building affected by the regulations to display a valid DEC in a prominent place clearly visible to the public at all times and possess a valid advisory report.

By 1 October 2008 if you are an occupier of a building requiring a DEC, you will need to display a DEC showing an Operational Rating in a prominent place clearly visible to the public. By 1 October 2008 you will also need to have in your possession or control a valid advisory report.

If you are a new occupier, or have been in occupation for less than 15 months by 1 October 2008, you may not have 12 months of meter readings available that are required for an Operational Rating. The legislation makes provisions for calculation over the period of occupation in these cases.

DECs must be renewed every 12 months.

How to get a DEC? Energy Assessment Process

Step 1: commission an assessor

Only energy assessor who are accredited to produce DEC for that type of building can produce a DEC and advisory report for your building.

Step 2: gather the relevant information

The occupier will need to obtain actual meter readings or consignment notes for all fuels used in the buildings that are affected by this legislation. This may include gas fuels, oil fuels, solid fuels, district heating and cooling, grid electricity and electricity generated on site or obtained by private distribution systems from other sites. The information sources include:

• on-site energy meters;
• the building landlord or representative;
• the utility supplier;
• the district heating/cooling provider.

Step 3: enter the information to an approved software

The energy consumption data provided will then be reviewed by the energy assessor in line with the approved methodology. Under certain conditions, the methodology allows adjustments to be made for longer hours of occupation, variations to weather and climate and allows certain activities to be separated if they are non-typical of the type of building (separable energy uses).

The carbon dioxide emissions for the certificate are based on the adjusted energy consumption and adjusted total useful floor area and building type to give a measured CO2 emission per square metre.

Step 4: produce DEC and advisory report

The energy assessor will then use an approved tool to calculate the Operational Rating and produce a DEC and advisory report from the information gathered in line with the approved methodology. The DEC and advisory report must be lodged in a national register and given a unique certificate reference number.