Evaluating window systems for decision support regarding the balance of daylight and heat gains

Designing windows requires dealing with the external environmental conditions, which may be conflicting, such as solar gains and daylight. This paper evaluates the performance of different alternatives for window systems to support design decisions on the balance of light and heat gains in the indoor environment, focusing on offices in a hot and humid climate. In order to do this, integrated computer simulations using the Daysim and EnergyPlus softwares were performed, considering the activation of electric lighting only when daylight was not sufficient to meet the usage requirements. The variables were window-to-wall ratio, glazing type and shading angle, simultaneously. Compromise solutions were found regarding the criteria of availability and uniformity of daylight and electricity demand in the indoor environment. It was observed that solar control through the use of shading devices presented substantially better results than solar control by reducing transmission of solar radiation by the glass. The assessment conducted contributes to increase understanding about the impact of different design variables on the phenomena characterising the performance of fenestration systems.

窗户设计需协调存在冲突的外部环境要素，例如太阳辐射得热与天然采光。本研究针对不同窗户系统方案的性能开展评估，旨在辅助室内环境光热平衡相关的设计决策，研究聚焦于湿热气候区的办公建筑。为此，本研究采用Daysim与EnergyPlus两款专业软件开展集成化数值模拟，模拟逻辑设定为：仅当天然采光无法满足使用需求时，方才启动人工照明系统。本次模拟同步考量三类设计变量：窗墙比、玻璃类型与遮阳角度。研究最终得到了兼顾室内天然采光充足性、均匀性与用电需求的折中优化方案。研究结果表明，采用遮阳装置实现太阳辐射控制的效果，显著优于通过降低玻璃太阳辐射透射率来达成的太阳辐射控制效果。本次评估有助于深化对各类设计变量影响门窗系统（fenestration systems）性能相关现象的作用机制的理解。