analysis of the influences of solar radiation and façade glazing ...

3.3 Estimation of thermal energy gain and loss through building fenestration 72
District heating [kWh]
30 000
29 000
28 000
27 000
26 000
25 000
24 000
23 000
22 000
21 000
20 000
design value
0 10 20 30 40 50
Window-Wall Ratio [%]
Fig. 3.21: Relationship between energy for space heating and window-to-wall area.
As it turned out, we could describe the relationship between the energy consumption for
space heating Eh and the window-to-wall ratio with a high level of accuracy by using the
following linear equation:
Eh = 210 , 8⋅WWR+
20262.
(3.1)
It is important to emphasize that it is impossible to find an optimal value of WWR if we use
this simple approach to the subject under examination.
It was proposed to find a procedure for determining the optimal value of the window-towall
ratio. This method consists of the three following steps:
I. calculation of energy balance for windows on each side of the building separately,
II. increase an area of the windows with the positive energy balance to the maximum
limit,
III. reduce the size of the windows with a negative energy balance to the minimal
value, which depends on the floor space for all living rooms.
Therefore, in the beginning it was necessary to examine each building façade separately.
Fig. 3.22 – Fig. 3.25 show the energy balance of the glazing systems for the north, south,
west and east faces of the building, respectively. Simulations were conducted for the
following five locations in Germany: Hannover, Berlin, Düsseldorf, Frankfurt and