Direct solar gains are significantly influenced by the glazing ratio. The simplest and most effective way for more solar gains is to have bigger glazing areas, which on the other hand also cause heat loss depending on the glazing type. For all building types the heating and cooling demand was calculated with various glazing ratios for different orientations. At first, the glazing ratio was only changed on one fagade, with fixed other glazing ratios. As a result, the heating demand increases strongest for the northern fagade, but hardly so for a southern fagade. As can be seen in Figure 18.15.1, a single-family house with no windows and a north fagade has 26% less heating demand
|
Figure 18.15.1 Heating and cooling demand (in kWh/m2 a) as a function of glazing ratio of a given fagade orientation for a single family house under Stuttgart/Germany climatic conditions. |
|
Figure 18.15.2 Heating and cooling demand (in kWh m-2 a) as a function of glazing ratio of a given fagade orientation for a multi family apartment block under Stuttgart climatic conditions. |
 |
Influence of solar gains and glazing ratio on heating and cooling demand for multifamily houses with different site densities.
than the single-family house with a totally glazed north fagade (65 kWhm-2 a-1 with no north fagade glazing compared to 93kWhm-2a-1 for the fully glazed northern fagade), whereas on the southern fagade the demand reduces by only 7% with reducing window area.
In multi-family houses (see Figure 18.15.2) the heating demand decreases from 67 to 38 kWhm-2 a-1 with decreasing northern glazing fraction; i. e. by 42%, and by 24% for high-rise buildings (from 62 to 47kWhm-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 construction 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 fagades, 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%.
