Intelligent Envelopes for High-Performance Buildings by Guedi Capeluto & Carlos Ernesto Ochoa

Author:Guedi Capeluto & Carlos Ernesto Ochoa
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

The solar collection envelope is defined for each project according to a definition of the self-shading period required, which is specific for each site. The critical date and time that shape SCE geometry may be different for each elevation depending on its orientation.

Calculations are carried out for the 21st day of every month, and for every hour during the predetermined required period. For each hour during this period, the azimuth and altitude of the sun are calculated.

Conceptually, the examined area has to be divided into a fine orthogonal mesh placed at the desired building height area, and the maximum height value from the zenith to the vertices of each of the mesh components, to the ground surface, need to be calculated. Joining all the point elements in space will determine the SCE surface.

This process of determining the protection angle and the building shape is not a simple task, particularly for non-rectangular building plans, or when the North axis is not parallel to the external walls. The required shading period for a window in a given orientation should be calculated as a result of parametric analysis, using dynamic hourly energy simulation models. Such analysis for different shading requirements gives the energy consumption for heating , cooling and lighting . After finishing calculation of the required shading period, it is possible to generate a building geometry that fulfills these requirements.

The longer the required self-shading period, the larger will be the wall inclination, in particular for east and west orientations. This also means a lower resulting building volume with a disproportionate roof area exposed to the sun. In order to decrease wall inclination and therefore roof area, designers may consider additional means such as deeper windows and the use of additional dynamic shading devices on the affected facades.

As an example, we present a study done for the city of Jerusalem (32°N 35°E), which was carried out using the SustArc simulation model (Capeluto and Shaviv idem). The calculations were carried out for a shading period based on the summer months (May to September) between 10.00 and 14.00 solar time. As the solar path is symmetrical for 22 June, the resulting shading period will be wider, including March and April. The daily self-shading period was limited to four hours around noon, in order to avoid very inclined facades.

As a way to prevent significant solar gains before 10:00 and after 14:00 in summer, additional shading devices should be considered by the designer. In cases when the aim is to protect the building during all the working hours, it may be required to run the model using the local standard time.

From Fig. 3.10, it can be observed that for the studied case, the SCE obtained is symmetrical with respect to the North-South axis. This explains that the resulting East and West facades result with the same inclination of 34 degrees from the zenith. However, this is not the case for the South and North facades.

Fig. 3.10Example of a SCE for a North-South oriented building in Jerusalem generated

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