Abstract
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.