Modulated solar shielding of buildings : a study of a solar radiation control strategy for low energy buildings in hot dry and semi-arid climates

This study investigated the use of modulated solar shielding in the context of solar radiation control in hot-dry and semi-arid climates. Solar shielding refers to the solar protection of the entire or large parts of the building's external fabric and not just those elements which directly transmit solar radiation. The study was undertaken with particular reference to the hot semi-arid climate of northern Nigeria. A conceptual and climatic analysis provided a contextual background for the work. A study of the use of shading devices indicated that their strength in some climates may be their weakness in others, especially the hot dry and semi and climates. A multiplicity of inherent climatic and environmental elements were not fully addressed by formal shading techniques. The concept of solar shielding was conceived from the interplay of the climatic and environmental factors of hot dry and semi-axid lands. Lack of measured solar radiation data in the reference climate necessitated the development of an interactive computer program to generate this and other relevant design data. A literature review provided a theoretical foundation un- derpining a series of full scale field measurements, scale model experimentation and thermal simulation studies. Fill scale measurements in a building were instructive on a possible impact of solar shielding on indoor thermal conditions. Model scale wind tunnel tests on the reference building and studies on full size louvres, using a pressurisation test facility, culminated in the development of airflow models through louvres. Finally, parametric thermal modelling studies enabled not only the optimisation of the technique but also a comparison with formal shading methods. Measured and simulated data portrayed not only a significant agreement but also indicated that solar shielding could have a higher solar protection efficiency than shading devices.