Browsing by Author "Meyer, Edmund Stanhope"

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    South African building envelope thermal performance simulation: parameters and the role of moisture content
    (2022-04) Meyer, Edmund Stanhope; Van Zijl, Gideon P. A. G.; De Villiers, Wibke; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: Literature tells of a connected, yet not well harmonised, narrative between building sustainability, building performance, building simulation and building regulations. Building simulation is actively used in industry to achieve targeted building ratings, but the targets do not always match reality due to the associated complexity and uncertainty associated with building simulation. This is further complicated by how the target is set for building performance, as many require an improvement over a benchmark value. For South Africa, the benchmark is provided by building standards. The need to investigate hygrothermal analysis for South African buildings is based on three observations. First, there is a lack of hygrothermal studies in South Africa. Second, conclusions drawn in the literature that focus on the thermal performance of South African low-income housing are based on 'what' environmental conditions are experienced and not 'why' specific environmental conditions are experienced. Third, although climate may be similar when comparing studies that focus on building performance, differences in results exist due to differences in the assumptions used for building simulation. The purpose of this study is to establish the case for improved building simulation and the regulation thereof in South Africa. To do so, four building models were adapted or created and modelled under specific conditions. The first two building models provide insight into how design choices influence the heating and cooling loads of two South African Green Star buildings when only considering heat-only analysis. Results indicate that providing high performance thermal insulation in combination with a large window-to- wall ratio will put additional strain on the air conditioning systems of the Green Star buildings. Furthermore, increasing the window-to-wall ratio of all glazed surfaces during analysis provides limited insight into the effect of the window-to-wall ratio of the Green Star buildings, unless considered alongside the changes to heat transfer through opaque building components, or considering specific surfaces. The third building model highlights the influence of moisture buffering materials on the environmental conditions of the building environment for a typical summer and winter week in South Africa. Results indicate that hygric materials directly influence the building environment. Furthermore, the sorption isotherm and initial moisture content of the material appear to influence simulation results significantly. Results indicate that if sufficient hygroscopic building materials are exposed (in terms of surface area and volume) to the South African environmental conditions, expected simulated results will be different, depending on the inclusion of moisture in heat transfer through building materials. The final building model serves as validation for the conclusions made regarding the importance of hygrothermal analysis. The model also highlights the need for improved modelling guidelines for South African buildings and additional requirements regarding buildings' material properties. The accuracy of the hygrothermal analysis, compared to heat-only analysis, confirms that hygrothermal analysis is required to accurately simulate the environmental conditions in South African buildings with moisture buffering components. Although results show the influence of moisture buffering materials on simulated temperature and relative humidity, further research is still required in South Africa to allow for independent hygrothermal analysis, i.e. hygrothermal analysis using South Africa specific data. Future research towards improved building simulation in South Africa should focus on expanding simulation input data provided for South African building performance simulation, as well as when hygrothermal modelling is needed.