Document Type : Research Paper
Authors
1 Architecture, Faculty of Art and Architecture, Tarbiat Modares University, Tehran, Iran
2 assistant professor/ Tarbiat modares university
Abstract
Windows, as one of the most influential facade elements, play a pivotal role in building energy performance and thermal comfort, accounting for 25-40% of heat losses in residential and commercial buildings. However, most previous studies have focused either solely on energy optimization or thermal comfort assessment, without simultaneously considering the life cycle environmental impacts. This research employs a comprehensive and integrated approach to evaluate the impact of various window characteristics, including window-to-wall ratio (WWR), glass type, and window orientation, on three criteria: energy efficiency, thermal comfort, and life cycle carbon emissions in an elementary school building in Yazd, Iran, with a hot and arid climate. Simulations were conducted across forty-eight scenarios using DesignBuilder software, based on variations in WWR (25%, 50%, 75%, and 100%), four orientations (north, south, east, and west), and three glass types (single-pane clear, low-emissivity double-pane, and low-emissivity triple-pane). Results indicate that low-E triple-pane glass with 25% WWR in north orientation achieves the lowest cooling energy consumption (38% reduction compared to single-pane glass), while clear single-pane glass with 100% WWR in south orientation demonstrates optimal heating performance (42% reduction in heating demand). From a thermal comfort perspective, low-E triple-pane glass provides the most stable conditions throughout all seasons, reducing the percentage of dissatisfied occupants from 55% to 45% during hot months. Life cycle assessment revealed that triple-pane glass reduces carbon dioxide emissions by 62% over the building's thirty-year lifespan compared to single-pane glass, making it the optimal choice for sustainable design in hot and arid climates. These findings demonstrate that proper window design, considering energy, comfort, and environmental criteria simultaneously, can provide an effective framework for sustainable buildings in similar climates.
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