Knowledgebase: DCLG Guide to EPC (ND)
What contributes to the energy performance of a building?
Posted by Mike Gordon on 22 July 2015 01:02 PM

The energy rating of a building is a complex calculation which is based on a combination

of factors. The key factors are:

the type of construction of the building (including walls, roofs, floors and glazing)

whether parts (zones) of the building are used for different purposes e.g. office, factory etc

and the occupancy profile for each zone

heating, cooling, ventilation and hot water systems used


The energy performance of non-dwellings is shown as a CO2 based index. The CO2

based rating a building receives depends on the energy used for space heating, water

heating, ventilation and lighting, less any energy generated from energy generation

technology installed in the building (such as solar water heating). The lower the number

the lower the typical CO2 emissions (based on a scale of zero to 150 +).

The rating is adjusted for the total useful floor area of a building (see glossary of terms

for a full definition) so it is independent of size for a given type of building.

The calculation process compares the carbon emissions of the building with those of a

reference building. The reference building is an equivalent building (i.e. a building of the

same size, shape and use as the actual building) constructed to a notional building

designed to a specified standard.