2.2. Specific energy use
Data on purchased energy use3 for space heating and hot water purposes and electricity use for the year 2012 was collected from the local energy utility Växjö Energi AB (VEAB) after obtaining permission from the building owners. The “heating degree days” method was used to normalize the impact of weather variations on the energy use for heating, which is the delivered district heat in all buildings and additionally normalized electricity to operate heat pumps in Pr-DH-HP buildings. For a Aberela temperature of 17 °C (used by the Swedish Meteorological and Hydrological Institute), the heating degree days for Växjö in 2012 was 3544 and that of a normal year (average of 1960–1990) was 3577 . The ratio 1.009 (degree days in a normal year divided by degree days in 2012) is the normalizing factor. The actual energy use for heating a building was multiplied by 1.009 to estimate the normalized energy use for heating.
Analyzing the objectives of this paper necessitated data on actual specific energy use of the buildings, which in turn required data on purchased energy for space heating, hot water, and electricity to operate the buildings (ventilation and heat pump) excluding for household purposes. In all the buildings, the use of district heat for space heating and hot water was recorded together (henceforth referred as “heating”) as delivered district heat. This was normalized without differentiating between energy use for space heating and hot water. A single meter recorded total household electricity of a building, because of which electricity use by the ventilation system and heat pumps was not available. Hence, electricity use for ventilation system was assumed to be 8 kW h/m2 Atemp/year  in all types of buildings. Then,specificenergyuseofaPr-DHandGr-DHbuilding=Normalizeddelivereddistrictheat+electricityusedtooperateventilationsystem.