School of Hard Rocks: Lessons out of Africa

The design of Harare International School in Zimbabwe generated a number of pioneering appropriate technologies of broader relevance. The most important of these are: • passive cooling of room supply air using buried rockstore compartments • passive ventilation using unique wind-driven fans Peak supply air passive cooling of up to 10°C (or 2/3rds of the diurnal swing) has been achieved through the rockstore scheme without impacting on system fan power requirements. The self-regulating wind-driven extractors achieve static pressure generation several orders of magnitude higher than other passive ventilation techniques, facilitating a greater range of passive ventilation applications than previously feasible. The scheme phases were delivered at capital costs less than that required for conventional air-conditioned schemes in Zimbabwe and required minimal amounts of scarce hard-currency. Energy costs in use are less than 10% of conventional and maintenance costs are also significantly reduced. Resource-efficient design was key to minimising both environmental and financial cost. Use of local materials and skills was crucial to achieving a robust and sustainable solution. Embodied energy, water and emissions/pollution are all minimised through this approach.