Utilisation of Passive Solar Energy - Renewable Energy: Technology, Economics and Environment - page 110

consider the inclined radiation incidence. This factor is taken into account by the
diffuse g -value in Table 3.2 and Table 3.3.
According to Equation (3.4), the solar heat generated within a defined period of
time within area Q S is thus calculated by multiplying the solar global radiation
incident on window G g,t,a , g -value and reduction factors, such as fixed and flexible
shading ( F S and F C ) (Table 3.4 and Table 3.5), contamination F D , and frame sec-
tion F F (Table 3.6).

Q = F F F F g G

(3.4) S S D F C g , t , a

Shading devices. By an appropriate building design, e.g. by balconies and projec-
tions, adequate shading protection from high-angle sun in summer can be pro-
vided without incurring any additional costs. The advantages of such fixed shad-
ing devices are simplicity and permanent function, as the devices lack moving
parts which would require special control. However, they are applied most easily
in a new building, where they can be incorporated into the original design, and
should be south facing to ensure good shading in summertime and high irradiation
into the building by the low-angle sun in winter (see Fig. 3.3). Even in summer-
time orientation to the east and west provides for high irradiation of the building
by the low-angle sun, whereas in wintertime irradiation for these orientations is
low (see Fig. 2.21). However, fixed shading devices reduce the efficiency of pas-
sive solar energy utilisation, as they also provide shading in-between seasons (in
spring and fall), when space heating systems are still required.

Well-insulated roof

South

Winter

Summer

Winter

Well-insulated roof

Living space with
insulating glazing
facing south

Summer

Optionally
glazed
loggia

Optional
sun space

Living space
with insulating
glazing facing
south

Thermal mass

Thermal mass

Fig. 3.3 Shading of transparent building surfaces by roof overhangs (left: single family
house, right: multi family house)

Shading of buildings thus depends on the following parameters or factors. For
a definition of the relevant angles refer to Fig. 3.4.