Energy Demand of Buildings - Low Energy Cooling for Sustainable Buildings - page 2

Figure 1.1 Distribution of end energy consumption within the European Union

The European Directive for Energy Performance of Buildings, signed by the
European Parliament and Council in 2002, was created to unify the diverse national
regulations and calculation methods, to define minimum common standards on build-
ing energy performance and to provide certification and inspection rules for a building
and its heating and cooling plants. Although the performance directive only defines
a common methodology for energy certification, most European countries have now
increased their requirements to limit new buildings' energy demand. On average,
allowed building transmission losses are now 25% lower. The heat transfer coeffi-
cient ( U -value) is defined as the reciprocal sum of heat transfer resistances between
room and ambient air and is today on average between 0.3 and 0.4 W m − 2 K − 1 for a

building.
The reduction of energy consumption in buildings is of high socioeconomic rel-
evance, with the construction sector as Europe's largest industrial employer repre-
senting an annual investment of 910

10 9 euros (2003), corresponding to 10% of
gross domestic product. Almost 2 million companies, 97% of them small and medium
enterprises, directly employ 11.8 million people.
The total primary energy consumption in Germany is about 4

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10 9 MWh, corres-
ponding to 13 878 PJ (2007 data), and is estimated to decrease by 15% until 2030
(EWI/Prognos, 2005). The main efficiency gains are expected through the reduction
of transformation losses, which today are responsible for 3984 PJ and are due to
decrease by 37% until 2030. In the building sector, on the contrary, the final energy
consumption of 2599 PJ (2000) is only estimated to decline by 4% until 2030, which
is due to the slow rate of rehabilitation.
In moderate European climates such as Germany's, about 80% of the total energy
consumption is used for space heating, 12% for warm water production and the rest
for electrical appliances, communication and lighting. The dominance of heat con-
sumption, almost 80% of the primary energy consumption of households, is caused by
low thermal insulation standards in existing buildings. They dominate the residential
building stock with 90% of all buildings. Even in 2050, 60% of residential space will be
located in existing buildings (Ministry for Transport and Buildings, Germany, 2000).
Since the 1970s' oil crises the heating energy demand, particularly of new buildings,
has been continuously reduced by gradually intensified energy legislation. With high

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