Abstract
A bioclimatic analysis of different South African towns and cities indicates that, if the correct mix of passive design principles is used, they all have a significant passive design potential. Of all such measures, solar protection and shading is the single most important passive design measure to reduce energy usage and to improve internal comfort for buildings in all South African climatic regions. The correct design of public open spaces and streets facilitates, to a great extent, energy-efficient buildings, whilst at the same time providing functional and comfortable urban open spaces and streets. Passive solar buildings aim to maintain interior thermal comfort throughout the sun’s diurnal and annual cycles, whilst reducing the requirement for active heating and cooling systems. The aim of this article is to investigate the effect of climate zones on passive design potential, of which shading design is an integral part, using Pretoria as a case study. This includes the effect of street width, building height, street layout, orientation, and the amount of sunlight available for trees and plants in the urban environment. The Spatial Planning and Land Management Act (2013), City of Tshwane Land Use Management By-law (2016) and the Tshwane Town-Planning Scheme 2008 (Revised 2014) were used as regulatory framework. To support the research, an Early Design Phase (EDP) experimental research platform was used to investigate the amount of sunlight on building facades with different orientations. This method enables the calculation of shading angles where there is a balance between the hot periods (requiring cooling) and cool periods (requiring heating) from the urban and building perspective. This has been achieved by means of the development of analytical software that uses weather files as one of the inputs to calculate critical solar angles. Over and above the calculation of current building solar protection angles, this method also facilitates the calculation of the increase in solar protection that will be required with climate change such as with the expected A2 climate change scenario (business-as-usual scenario) for South Africa. To support the EDP analysis, detailed simulations were also undertaken by means of Ecotect v5.60. Keywords : Cities, climate change, natural daylight, shade, sun, South Africa
Highlights
At about the same time that two prominent medieval European cities, Paris and Barcelona, were drastically transformed and improved, Pretoria was founded in 1855 by Marthinus Pretorius, who named the town after his father Andries Pretorius (Figure 5).Any discussion of public open-space policy should start with the work of early pioneers such as Baron Georges-Eugène Haussmann, Prefect of the Seine from 1852 to 1869 during the Second Empire, the reign of Napoleon III (Barnett, 1982: 163)
To study the effect of building height and street width on the availability of sunlight and natural daylight in the Pretoria CBD, a simulation model was defined by means of the Ecotect v5.60 energy simulation software
South Africa’s current climate is predominantly arid, with 70.9% of the area falling in the Köppen-Geiger categories BSh, BSk, BWh en BWk (Conradie, 2012: 181-195)
Summary
Cities contribute significantly to global greenhouse gas emissions and are adversely affected by the effects of climate change caused by these emissions such as the complex problem of Urban Heat Island (UHI) effect. From 2007 to 2009, the recorded building plans passed by South African municipalities for residential buildings, non-residential buildings and additions totalled 61,939,720 m2, with a value of R 231 250 619 000 or approximately US $33,8 billion (using January 2011 exchange rates) These amounts indicate the extent of formal growth in the South African built environment, and the increasing contribution thereof to building activity on the African continent (Laubscher, 2011: 68). The latter figures were calculated by means of a bioclimatic analysis with Climate Consultant 6.0, using weather files generated by means of Meteonorm v7.2.1.
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