Optimization of window area in buildings from the viewpoint of energy efficiency - Kabul, Afghanistan

Abstract

The proportion of window area on a building façade is one of the key energy-saving design parameters affecting indoor thermal comfort, and the energy performance of a building. To avoid excessive energy loss or gain, determining the optimal window size is essential. Accordingly, this paper aims to investigate the impact of the Window-to-Wall ratio (WWR) of all sixteen cardinal, intercardinal, and secondary intercardinal directions on the energy consumption of buildings in Kabul, Afghanistan. Simulation models were built and analyzed using BEopt™ energy simulation software. The results indicate that in the climatic condition of Kabul, windows only on southeast, south-southeast, south, and south-southwest façades have energy-saving potential while providing windows on other facades results in higher energy demands compared to windowless façades. The total energy demand graph of the room with various WWR on southeast, south-southeast, south, and south-southwest façades form a U-shaped curve with a minimum value when the WWR is 0.15, 0.3, 0.35, and 0.25 respectively. The maximum amount of energy saving achieved by WWR optimization is 6.5%. However, adding windows of up to WWR-0.7 to other facades increases energy consumption by up to 29%. The study concludes that optimization of WWR in different orientations during the design process will contribute to the reduction of heating and cooling energy consumption.