M.Sc. / South Africa is in the midst of an energy crisis. The national energy provider is unable to provide the capacity currently demanded in South Africa. Although the construction of new electricity plants is planned, it does not solve the immediate problem. A large amount of energy is used to provide thermally comfortable indoor environments using conventional methods such as air-conditioning units. Energy efficiency is an environmentally friendly solution for South Africans to reduce the demand for electricity. In the context of the current situation in South Africa, significance can be given to investigations that explore viable methods of reducing energy consumption in buildings, while maintaining or improving thermal performance through passive energy interventions. This study was conducted with the goal of quantifying and demonstrating technologies that simultaneously attempt to improve energy efficiency (through avoiding the use of energy intensive heating/cooling units) and improving the physical learning environment in prefabricated classrooms in South Africa, through the use of passive energy retrofits. This study forms one of the initial case studies conducted within the framework of the Enerkey Sustainable Megacities pilot programme. Reflective roof coatings and ceiling insulation were used to retrofit eight prefabricated classrooms at Garsfontein Primary School, Tshwane. Monitoring was performed of temperature conditions in two control and eight experimental classrooms. The resulting data were used to compare the thermal performance of the altered classrooms to the control classrooms. Empirical data sets included hourly average temperature readings in ten prefabricated classrooms and an externally located weather station. Average diurnal temperatures and temperature difference plots were created. A pre-retrofit questionnaire to determine occupants’ perceptions on the thermal indoor environments was distributed. Spot measurements of illumination levels in all ten classrooms were taken with a Lux meter. A cost-effectiveness analysis of the passive energy interventions was performed, using as a reference case an electrically powered air conditioning unit, specified to cool a 50 m2 classroom. Overall, the reflective roof coatings were not effective at reducing peak summer temperatures. A 50 mm thick plastic fibre insulation layer installed in the ceiling spaces consistently reduced peak indoor temperatures by ~2°C, while 50 mm thick expanded polystyrene ceiling boards were the most effective of the retrofits, consistently reducing peak indoor air temperatures by ~3°C. An analysis of the cost-effectiveness of passive interventions showed that, in comparison to the proposed alternative of installing electrically powered air-conditioning units, ceiling insulation is cost effective in varying extents, depending on the assumptions. However, in all cases considered, the cost advantage, expressed as Rand per degree Celsius comfort improvement, is considerable compared to the air conditioning unit. Light measurements indicated non-uniform illumination in the tested classrooms, from severe glare next to south facing windows, to dark areas well below minimum recommended levels. The overall illumination situation is unsatisfactory. Opportunities exist for improving illumination using passive and active energy efficient interventions. The hypothesis for this study was that passive energy interventions in prefabricated classrooms are energy- and cost-efficient means for improving the physical learning environment in South African schools. Ceiling insulation makes a valuable contribution towards improving indoor thermal environments in prefabricated classrooms. Ceiling insulation by itself, however, does not provide a comprehensive solution – the entire building envelope needs to be taken into consideration. A building energy digital simulation model could explore a range of interventions, to derive the overall most costeffective solution to improving indoor thermal environments in South African schools. Investigations of this nature will be conducted as part of the ongoing larger Enerkey project.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:6679 |
| Date | 16 March 2010 |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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