Utilisation of Passive Solar Energy - Renewable Energy: Technology, Economics and Environment - page 112

In Table 3.6 are illustrated some examples of shading factors F C for flexible shad-
ings, corresponding to various types of adjustable shading equipment, along with
the corresponding orientation.

Table 3.5 Shading factor corresponding to shading by overhangs ( F o ) and by overhangs
(fins) ( F f ) for different latitudes, window orientations and horizon angles (S south, E east,
W west, N north; for angle definition see Fig. 3.4; refer to /3-3/)
Angle

Latitude 45° Latitude 55° Latitude 65°

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

Shading by overhangs ( F o )
0° a
30° a
45° a
60° a

1.00
0.90
0.74
0.50

1.00
0.89
0.76
0.58

1.00
0.91
0.80
0.66

1.00
0.93
0.80
0.60

1.00
0.91
0.79
0.61

1.00
0.91
0.80
0.65

1.00
0.95
0.85
0.66

1.00
0.92
0.81
0.65

1.00
0.90
0.80
0.66

Shading by projections ( F f )
0° b
30° b
45° b
60° b

1.00
0.94
0.84
0.72

1.00
0.92
0.84
0.75

1.00
1.00
1.00
1.00

1.00
0.94
0.86
0.74

1.00
0.91
0.83
0.75

1.00
0.99
0.99
0.99

1.00
0.94
0.85
0.73

1.00
0.90
0.82
0.73

1.00
0.98
0.98
0.98

a overhang angle; b angle of lateral projections

Table 3.6 Shading factors F C of selected internal and external shading devices /3-3/
Optical properties Shading devices Shading factor

Ab-
sorption

Trans-
mission

Internal
shading devices

External
shading devices

White window blinds 0.1 0.05

0.1
0.3
0.5
0.7
0.9
0.1
0.3
0.5
0.05

0.25
0.30
0.45
0.65
0.80
0.95
0.42
0.57
0.77
0.20

0.10
0.15
0.35
0.55
0.75
0.95
0.17
0.37
0.57
0.08

0.1

White cloth

0.3 Coloured cloth

0.2 Aluminium-coated cloth

As an example, Fig. 3.5 illustrates the room temperature of a building calcu-
lated by dynamic building simulation for both cases, without shading devices and
for two different shading methods in the course of one week in summer and ambi-
ent temperature θ e ranging from 12 to 27 °C. Passive solar heat gains have been
considered. However, for the example, active air cooling is assumed for room
temperatures above 26 °C; room temperature θ i will thus not increase beyond this
value. The figure shows furthermore, that internal window blinds can only slightly
reduce the inside temperature, whereas external blinds can reduce the inside tem-
perature by several degrees Kelvin. In the present case, no additional cooling is
required when using external window blinds.