Figure 3.14 Building with compact form

The solar insolation and regional thermal stress influence the form of the building. In colder climates, the buildings` should have a more compact form, while in regions with heavy radiation impact, the buildings should have elongated shape with an east-west axis.

In the northern hemisphere, the buildings` south facade can receive almost twice as much solar radiation in winter than in summer. This ratio can be even larger in the southern latitude, resulting in a one to 4 ratio. On the other hand, the east and west facade can receive up to 2.5 times more amount of solar insolation in summer than in winter. For comparison, in summer the east and west facades can receive 2 to 3 times more insolation than the south facade. The roof facade receives the largest amount of insolation compared to the others.

The aspect of building form can be described by various parameters some of which offer better description of the interdependent of the form and buildings` performance. These parameters are:

 plan ratio  compactness  form factor

Figure 3.14Building with compact form15

Plan ratio

Optimal plan ratio of a residential building is recommended relative to the climate zone of the building[45]. The general rule is that the square house is not the optimum plan ratio in any location, rather an elongated form with an axis of the elongation to be east-west.

The ratio of the length of the building is given for the summer and winter period as a near optimal ratio, with a degree of flexibility, such as:

 In cool climate the winter optimal plan ratio is 1:1.1 and the summer is 1:1.4.  In temperate climate, the winter optimal plan ratio is 1:1.56 and with summer optimal ratio is 1:1.6. The ratio can be up to 1:2.4.