Developing Parametric Solar Envelope for Ethiopian Cities

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Addis Ababa University


The effects of poorly designed buildings in terms of limited access to sunlight on critical times affect the health of building occupants and become the growing concerns about global warming, Ozone layer, depletion of fossil energy source and soaring oil prices. So, planning in a way to allow for sun access by regulating the form, height, orientation and organization of the built environment is important. This paper deals about the design and applicability of solar envelope to residential houses of Ethiopian cities to get access for solar or shade right. Solar envelope is a building volume limit that will not cast shadows on surrounding buildings at specified times so as to create comfortable indoor climate for humans based on the sun’s movement (time) relative to the location and geometry of a site (space). The concept of solar envelope was first developed as a framework for architecture and urban design at the University of Southern California (USC) over the period 1969 to 1971 by Professor Ralph Knowles. For this end, NCEP stations found all over the country were tapped and their heating and cooling degree days have been computed correlating the respective temperature with the standard base temperature, 18.3 o c. Besides, reference cities were identified after the regionalizing Ethiopia based on their respective degree days. Then, sun path diagram for each region has been prepared and used to identify the critical sun angles, Azimuth and Altitude of the sun, for the specified time ranges. Finally, parametric solar envelopes have been developed for each zone of reference city and this will be a basic for energy efficient envelope building creation.



Solar right,, Shade right,, Solar envelope,, Heating and Cooling Degree Days,, Base temperature