Environmental Design of Buildings

When designing a building in 2023, we have a wealth of options to choose from to moderate temperature, improve daylighting, and provide ventilation. Modern building services can provide a tightly controlled, comfortable environment, and are increasingly energy efficient. But what if we don’t have access to HVAC systems? What should we rely on in the absence of a modern façade, with mechanically controlled louvres, thermally efficient fabric and insulated glazing? Passive design techniques offer a wide range of low-cost, low-carbon design solutions that are becoming increasingly important in the global effort to reduce carbon emissions from the built environment. Utilising the natural resources of the sun, wind, and light, whilst adopting a ‘fabric first’ approach to design can mitigate or even eliminate the requirement for building services. This approach is particularly pertinent to the design of low-cost housing. In the Monkey Bay district of Malawi, South-East Africa, homes are typically built from brick or fired clay, with the corrugated sheet metal roofing that is ubiquitous across sub-Saharan Africa.

Housing in this area is built in a style largely inconsistent with the vernacular architecture of the region, which has been shown to frequently perform better than modern dwellings, owing to centuries of accumulated passive design knowledge (Widera, 2021). In this building physics analysis, we apply these principles to a simulation of a dwelling in Monkey Bay. It is demonstrated that applying the simple passive design techniques of solar shading, alignment of openings with the prevailing wind direction, and optimising the window size for increased airflow with reduced solar heat gains, can result in a reduction in peak temperatures on a summer design day of up to 5 degrees. This is highly significant, as the temperature is maintained within a comfortable range for longer and prevented from crossing the heat stroke threshold. Increased airflow across aligned openings increases the interior air speed by up to 1.8x.

Cross-ventilation of the space extends the upper comfort temperature limit by 1-2 degrees and improves the interior air quality. Here, any interventions to improve quality of life must be low-cost or free, and passive design provides powerful solutions. Occupants can be spared from heat strokes for the price of a few sheets of board for solar shading, and careful design that doesn’t increase material costs. Passive design has the potential to reduce energy expenditure and carbon emissions, but also improve the life quality for millions of people without access to building services and modern materials. (Widera, B. 2021). Comparative analysis of user comfort and thermal performance of six types of vernacular dwellings as the first step towards climate resilient, sustainable and bioclimatic architecture in western sub-Saharan Africa. (Renewable and Sustainable Energy Reviews 140, p. 110736. doi: https://doi.org/10.1016/j.rser.2021.110736.)

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