Evaluation of natural ventilation strategies in school classrooms in a humid subtropical climate

Abstract Classrooms are long-stay environments, in which thermal comfort is fundamental to the teaching and learning process. In the context of Covid-19, higher rates of natural ventilation are required, which can affect thermal comfort. This research aimed to investigate 16 natural ventilation strategies in elementary school classrooms regarding energy efficiency, thermal comfort and quality of natural ventilation, in a humid subtropical climate, represented by the city of Santa Maria, RS, considering recommendations from the Federal Government and computer simulations with Ansys CFX ® and EnergyPlus. The following items were analysed: hours spent in thermal comfort, discomfort degree-hours, indoor air velocity, air renewal rates and air humidity. Strategies using cross ventilation and solar chimney, or north-south unilateral ventilation connected to open circulation met the criteria for air renewal, albeit with a 20% or more hours of discomfort due to cold. It was observed that sufficient natural ventilation causes discomfort due to excessive cold. The contribution of this project is to suggest more adequate natural ventilation strategies for classrooms located in humid subtropical climates, demonstrating that they can contribute to improve the quality of natural ventilation compared to conventional solutions.

摘要 教室是人员长期停留的室内环境，热舒适对教学与学习过程至关重要。在新冠疫情背景下，自然通风换气率需提升，而这可能对热舒适产生不利影响。本研究以巴西南里奥格兰德州圣玛丽亚市为代表的亚热带湿润气候场景为研究载体，针对小学教室的16种自然通风策略展开系统性研究，从能效、热舒适表现与自然通风质量三个维度进行考量；研究过程参考巴西联邦政府相关规范建议，并采用Ansys CFX®与EnergyPlus两款软件开展计算机仿真分析。本次研究分析的指标包括：热舒适时长、不舒适度时数、室内空气流速、新风换气率与空气湿度。结果表明，采用交叉通风与太阳能烟囱，或结合开放通廊的南北单侧通风的策略，均满足新风换气标准，但因低温导致的不舒适时长占比达20%及以上。研究发现，过度充足的自然通风会因室温过低引发热不舒适问题。本研究的核心贡献在于，为亚热带湿润气候区的教室提出了更适配的自然通风策略，并证实相较于传统通风方案，此类策略可有效提升自然通风质量。