ABSTRACT
Designing to make use of the climatic conditions of the site has always been a Challenge, especially for energy efficient building. The current investigation assesses how effective orientation, window-wall ratio and types of windows as a parameter for the reduction of annual cooling energy demand and the annual total energy consumption in commercial buildings. The research approach is experimental where study of commercial building in northwest Nigeria is analysed with parametric analysis. Simulation with Ecotect software applied is conducted. The results predict annual cooling load for the energy demand is 164.6kWh/mÂ�yr; a reduction of 20.7kWh/mÂ�yr when optimum orientation is used away from the actual. Again, results show that the total energy consumption increased when the window-wall ratio is also increased, in terms of annual cooling loads per unit floor areas, 60:70% window-wall ratio performed better. In addition, energy consumption in east and west axis is a little more (around 2-3%) it appears more obvious when the window orientation is east or west than north orientation. Energy consumption in South orientation corresponds to maximum annual cooling energy demand and it is minimum for north orientation. This fact-finding holds good. Annual energy consumption load for east and west orientation are almost equal (within 1% variation). Furthermore, in terms of energy efficiency, double glass with aerogel filled performs better than low-emissivity (Low-E) glass. For 90% increment in glazed area, the corresponding increase in energy consumption is 13.3 kWh/m2yr for single-clear, 11.1 kWh/m2yr for double clear, 8.7 kWh/m2yr for double low-e-clear, 5.3 kWh/m2yr for solar control reflective, and for 2.3 kWh/m2yr double glazing aerogel filled. From this study, it can be concluded that the influence and sensitivity of window-wall ratio on the total energy consumption are related to the orientation of outside window, and the glazing types of window. The influence of the factors can be regarded as reference mode for the window-wall ratio when designing commercial buildings. This indicates that if attention is paid to orientation and window-wall ratio as parameters during the design of a shopping malls, it would go a long way in ensuring that the design save cost to user. It recommended that Windows facing the east and west contribute to the greater effect on the energy consumption. Windows facing east or west should be avoided or the window-wall ratio of them should be limited, and external windows with suitable shading coefficient should be applied or movable sun-shading for the windows should be set up. In consideration of the building energy efficiency design, the windows should be on the north façade or the south and ventilation and natural lighting need to be considered. Reducing the window-wall ratios of a commercial buildings in northwest Nigeria would provide significant energy saving benefits. The energy efficiency performance would be significantly increased by reducing the window-wall ratio for external windows of single glass compared to when it is double glass-aerogel filled.