Reducing heat stress exposure : retrofit shading strategies for informal dwellings in Tshwane, South Africa

Abstract

The average temperature in South Africa is increasing at nearly twice the global rate. South Africa also has a large population living in informal settlements characterised by inadequate housing with poor thermal regulation. This population is consequently particularly vulnerable to the risks of increased heat stress exposure, underscoring the need to develop well informed, contextually appropriate heat stress adaptation strategies. One of such is the use of solar shading devices that block solar radiation, which after a literature review prove to have an increased potential in reducing indoor dwelling temperatures. The study therefore investigated the performance effectiveness of static and adaptive shading strategies. This was achieved by digitally simulating fourteen static shading strategies applied to a prototypical informal dwelling in Tshwane. An adaptive shading strategy with rotatable louvres was developed based on the synthesised results and was further tested in both virtual and in situ environments. The results of each were comparatively discussed using a control dwelling, and the accuracy of the digitally simulated data was compared to in situ measured data. The findings indicate that the performance of solar shading strategies is not directly proportional to the material surface area, suggesting that the availability of resources should be the first informant when developing shading strategies in informal contexts. The findings also present built environment professionals and informal settlement inhabitants with a practical guide to optimise shading performance. The roof is the most important building envelope surface to shade on an annual time scale, yet seasonal adaptive shading proves to reduce heat stress exposure significantly. This is accomplished by prioritising shading devices based on available resources and applying them to the surface with the highest thermal gain, while using optimal fin orientation. The results finally indicate that despite observed differences in absolute values, digital simulation is an effective method to verify design choices and optimise solar shading strategies. This study provides data and evidence to support a limited field encompassing locally appropriate heat stress adaptation strategies within informal contexts.