Solar energy use in buildings - Solar Energy Sciences and Engineering Applications - page 620

In multi-family houses (see Figure 18.15.2) the heating demand decreases from
67 to 38 kWh m − 2 a − 1 with decreasing northern glazing fraction; i.e. by 42%, and by
24% for high-rise buildings (from 62 to 47 kWh m − 2 a − 1 ), as shown in Figure 18.15.3.
In order to understand the importance of glazing ratios in relation to urban density,
three types of glazing ratios were evaluated in four different site densities and the results
are represented in Figure 18.15.4. As a reference scenario, typical glazing ratios from
the German building typology were used for the different building types and their con-
struction year (30% for the single-family building, 30% for the multi-family building,
32% for the high-rise apartment blocks, 16% for terraced housing and 17% for the
old apartment house). When the glazing ratio is increased on all façades, the heating
demand increases with increasing site density. The cooling demand nearly doubles
with high glazing fractions and again decreases with increasing site density. Higher
site densities increase the heating demand by 12% to 18%, but reduce cooling by
up to 50%.
18.16 OFFICE BUILDINGS IN AN URBAN CONTEXT
The heating, cooling and lighting energy demands of office buildings were analysed
as a function of urban density (see Figure 18.16.1). As the characteristic parameter,
the height of the building H related to the distance between buildings W was used.
The office building type investigated is a cellular plan office with a building envelope
designed to a low-energy standard following the German Energy Saving Ordinance
2009.
Figure 18.16.2 shows total annual energy demand of a south-oriented sample office
space under four different aspect ratio (H/W) scenarios in southern German climatic
conditions. Figure 18.16.2 shows that the total energy demand increases by 20% when
the H/W ratio changes from 0.5 to 1 due to an increase in heating energy demand. The
total energy demand then slightly decreases by 6% with aspect ratios above 1 as the
cooling energy demand decreases.
Figure 18.16.1 The form structure labels H, D and L 1 refer to the height, depth and frontal length of
each unit, L 2 refers to the spacing between the units andW to the width of the street.