Dwelling Emission Rate (DER) Is equal to CO2 emissions per unit floor area for space and water heating and lighting less emissions saved by energy generation Is equal to CO2 emissions per unit floor area for space and water heating and lighting less emissions saved by energy generation New dwellings & extensions New dwellings & extensions Non Dwellings & large dwellings >450m 2 Non Dwellings & large dwellings >450m 2 Building Emission Rate Building Emission Rate