Sustainable Building Operation Using Simulation - Low Energy Cooling for Sustainable Buildings - page 231

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Real consumption Calculation EN 832 n =0.7 Calculation DIN V 18599 n =0.4 WW

Figure 6.30 Monthly heating energy consumption degree day corrected and compared with calculated
consumption for air changes of 0.7 and 0.4 h − 1 . In addition the measured warmwater consumption (WW)
is shown

energy balance from EN 832, but which allows more detailed zoning of the building.
The results indicate that the real air exchange rate of the naturally ventilated building
is related to the outside temperature, which should be considered in further models.
The same effect was analysed for rehabilitated residential buildings in the Scharn-
hauser Park area (see Figure 6.31), where winter energy consumption could be well
modelled with a reduced air exchange of 0.35 h − 1 , whereas in spring months a higher
air exchange of 0.7 h − 1 gave good agreement with measurement data. Before the
buildings were renovated, the higher air exchange rates gave good results; however,
the higher airtightness of the new windows led to low air exchange rates especially in
the cold winter months. During spring and autumn, on the other hand, the consumption
is underestimated if the air exchange rate is kept at the lower value of 0.35 h − 1 (see

Figure 6.32).
To compare measured consumption results E c,measured from several years, it is stan-
dard practice to normalize the measured heating energy consumption using the actual
degree day G 15 compared with the long-time average degree day G 15 m (see e.g. the
German standard VDI 3807). If such a degree day correction is carried out, based on
temperature differences relative to 15 ◦ C, the maximum difference in annual heating
energy consumption reduces from 21% for the uncorrected values to 15%:

E c,measured G 15 m
G 15

E c,normalized = (6.16)