A Comparative Study of the Performance of Selected Shading Techniques

Solar shading is one of the cheapest passive cooling techniques employed in hot climates. There is nowadays quite a large number of designs and configurations of shading devices available for architects to use. A lot of work has been done to examine the effect of such shading techniques on space cooling loads. Most of the work found, actually examines the distribution of sunlight on external building surfaces. In regions with both cooling and heating requirements, it becomes important for building designers, to know the impact of solar shading techniques on building thermal performance throughout the year. There is an obvious need for reducing the exposure of indoor surfaces to direct sunlight in the cooling season. But there is also a need to maximise the exposure of such surface to direct sunlight for passive heating in the heating season. Literature search has shown a clear need for more comprehensive work to produce useful and more specific data relevant to shading techniques and their impact on indoor sunlight distribution and consequently cooling and heating loads, throughout the year. This is the main field for the present research which is partially described in this paper. This paper evaluates the performance of different shading techniques using a computer program “SunCast” which is a well known model developed in the UK as part of a large suite of programs. SunCast has already been used for more than a decade, by many researchers to investigate the solar performance of building components. Experiments explained in this paper were, first, conducted to gain confidence in the SunCast model by comparing its results against independent full scale tests. The paper then examines criteria and techniques that can be used to evaluate the effects of variables like latitude, orientation, and other factors on the distribution of sunlight inside a space. A study is carried out later to evaluate the effect of the indoor sunlit area on the resulting cooling and heating loads and indoor temperature. The last part discusses a thermal simulation for different shading techniques in different climatic zones. Two climatic regions have been selected for the experiments; these were Riyadh, Saudi Arabia, representing a hot climate zones, and London, United Kingdom, representing a cold climate zones. The selection of two climatic zones could help in predicting more useful evaluation of the shading techniques. This evaluation could explain the contribution of the selected shading techniques in reducing or increasing heat gain or loss in both climatic zones in summer and winter.