Energy Demand of Buildings - Low Energy Cooling for Sustainable Buildings - page 6

Figure 1.4 Measured heating energy consumption for newly built rows of houses in Ostfildern,
Germany
Although 20% of all buildings in Germany were constructed after 1980, they only
consume 5% of the total heating energy. Depending on building age and type, older
buildings' heating energy consumption varies between 100 and 400 kWh m − 2 a − 1 . The
main challenge of the next decades will therefore be the reduction of heating energy
consumption for existing buildings.
Within the POLYCITY project the existing building stock of the town of Cerdanyola
near Barcelona in Spain was analysed with over 6000 buildings: 44% of them are
single storey buildings, 28% have two floors. More than 90% of the buildings were
constructed after 1960 and 65% of the apartments are between 60 and 90 m 2 . The
average heating energy consumption is between 90 and 100 kWh m − 2 a − 1 and has
increased slightly during the last decade due to increased use of central heating systems
with integrated warm water production (see Figure 1.7). In comparison, in the urban
area of Barcelona with multi-family apartment blocks, heating energy consumption is
only 34 kWh m − 2 a − 1 on average (Reol, 2005).
1.1.2 Domestic Hot Water
Independent of the level of insulation, water heating is always necessary in residen-
tial buildings. The energy consumption is between about 220 (low requirement) and
1750 kWh per person and year (high requirement), depending on the pattern of con-
sumption. For the middle requirement range of 30-60 litres per person and day, with
a warm water temperature of 45 ◦ C, the consumption is 440-880 kWh per person
or 1760-3520 kWh for an average four-person household. Related to a square metre
of heated residential space, a rather low average value of 12.5 kWh m − 2 a − 1 is for
example used in German legislation. In Switzerland, a fixed value of 14 kWh m − 2 a − 1