A DEC (Display Energy Certificate) measures the actual energy consumption of a building over a 12-month period, and compares it with other buildings of a similar type.
A survey is carried out to calculate the floor area for each activity type within the building, e.g. offices, kitchens, teaching spaces, sports halls, etc. The survey also includes details of the type of heating and hot water systems, lighting, glazing and other items. The surveyor needs access to all parts of the building, including plant rooms and roof spaces.
The annual energy consumption of the building for a 12-month period is then calculated, either from data collected by the client’s Automated Meter Reading systems or from the gas and electricity suppliers’ bills.
Government-approved software is then used to produce a DEC Operational Rating, based on the energy consumption per square metre, and taking into account the weather conditions during that 12-month period (so that, for example, high consumption during an unusually cold winter doesn’t produce an artificially poor rating).
The DEC process also includes preparation of an Advisory Report. This suggests ways to improve the energy efficiency of the building, and potentially therefore to save money on fuel bills.
The DEC must be displayed in a prominent place, clearly visible to members of the public.
For buildings larger than 1000m2 the DEC must be renewed annually. For smaller buildings the DEC is valid for 10 years.