For the purposes of Display Energy Certificates, a building must have a roof, walls and use energy to condition the indoor climate. This is the case where the building has any of the following fixed services:
- Cooling; and/or
- Mechanical ventilation (this means the supply of fresh air and extraction of stale air – not just an extraction fan).
It is not uncommon for a site to have multiple buildings or a large building built is multiple phases. If two or more buildings on the same site are linked by a fully enclosed structure consisting of a roof and walls, even if the link is not itself conditioned, then the combined buildings can be considered a single building for DEC purposes providing they have not been designed or altered to be used separately (usually by separate occupiers). This approach is particularly sensible when the different parts are serviced by the same common systems and where sufficient sub-metering is not in place. However, they may still be treated separately which can be useful in identifying energy efficiency improvements and monitoring energy usage.
NB: Since February 2009 site based DECs and ARs no longer meet the requirements of the legislation. All qualifying buildings on a site must now have their own Display Energy Certificate and Advisory Report.