Utilisation of Passive Solar Energy - Renewable Energy: Technology, Economics and Environment - page 111

− Shading by the horizon F h : determined by the solar position plot (see Fig. 2.20)
or according to Table 3.4.
− Shading by projecting structures: overhangs F o and side overhangs (fins) F f are
distinguished (Table 3.5).
The so-called shading factor F S covers the entire shading. According to Equation
(3.5), it is composed of the horizon shading factor F h , the shading factors of over-
hangs F o and side overhangs F f . Dynamic building simulations allow for a more
precise determination of the total shading of a building than this simplified equa-
tion.

F = F F F

(3.5)

S h o f

Table 3.4 Part of shading factor to determine the shading by the horizon F h for different
latitudes, window orientations and horizon angle (S south, E east, W west, N north; see e.g.
/3-3/)
Horizon angle Latitude 45° Latitude 55° Latitude 65°

S E/W N S E/W N S E/W N

0°
10°
20°
30°
40°

1.00
0.97
0.85
0.62
0.46

1.00
0.95
0.82
0.70
0.61

1.00
1.00
0.98
0.94
0.90

1.00
0.94
0.68
0.49
0.40

1.00
0.92
0.75
0.62
0.56

1.00
0.99
0.95
0.92
0.89

1.00
0.86
0.58
0.41
0.29

1.00
0.89
0.68
0.54
0.49

1.00
0.97
0.93
0.89
0,85

Definition of F h Definition of F o Definition of F f

Horizon
angle Angle of lateral

projections

Overhang
angle

Vertical
section

Horizontal-section

Fig. 3.4 Definition of angles corresponding to different kinds of shading (left: angle corre-
sponding to the horizon shading factor F h ; centre: angle corresponding to the overhang
shading factor F o ; right: angle corresponding to the shading factor F f of side overhangs
(fins); see /3-3/)

Besides the described fixed shading elements, also adjustable shading devices
are used for passive solar system control. If the solar heat gain exceeds, for in-
stance, the heat demand of a living space to be covered by solar resources, the
solar aperture surface can be shaded to prevent overheating. External shading
elements, such as window blinds and shutters, re-transmit the absorbed radiant
heat to the ambient air, and are thus often more efficient than internal shading
equipment. However, internal shading equipment (such as shutters and drapes)
does not have to be weatherproof and is thus less demanding in terms of design.