Ventilation rates in California classrooms: Why many recent HVAC retrofits are not delivering sufficient ventilation
Ventilation rates in California classrooms: Why many recent HVAC retrofits are not delivering sufficient ventilation
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DOI：
10.1016/j.buildenv.2019.106426
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发表时间：
2020-01-01
影响因子：
7.4
通讯作者：
Modera, Mark
中科院分区：
文献类型：
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作者：
Chan, Wanyu R.;Li, Xiwang;Modera, Mark
先前的研究表明，教室通风不足很常见，会对学生的健康和学习产生负面影响。为了加深对影响因素的了解，本研究走访了 11 所学校的 104 间教室，这些教室最近安装了新的供暖、通风和空调 (HVAC) 装置。对每个教室的二氧化碳浓度、房间和送风温度、相对湿度以及开门情况进行了四个星期的测量。现场检查发现 51% 的研究教室存在暖通空调设备、风扇控制和/或过滤器维护问题。在拥有有效数据的 94 个教室中，上课期间测得的平均二氧化碳浓度为 895 ppm，标准偏差 (SD) 为 263 ppm。根据每间教室每日最大 15 分钟二氧化碳排放量估算，94 间教室的通风率 (VR) 平均值为 5.2 升/秒，标准差为 2.0 升/秒。配备节能器的教室，无论是否配备需求控制通风 (DCV)，平均二氧化碳浓度往往较低。设备选择不当、缺乏调试、风扇控制设置不正确以及维护问题（过滤器负载过重）都与教室通风不良有关。此样本中的许多教室经常过于温暖，无法支持学习。 103间教室中有23间在超过20%的上课时间里室内气温在25.6摄氏度以上。需要更好地监督暖通空调系统的安装和调试，以确保教室通风充足。建议定期测试通风系统和/或连续实时二氧化碳监测（作为独立监测器或纳入恒温器）以检测和纠正通风问题。
Previous research has shown that under-ventilation of classrooms is common and negatively impacts student health and learning. To advance understanding of contributing factors, this study visited 104 classrooms from 11 schools that had recently been retrofitted with new heating, ventilation, and air-conditioning (HVAC) units. CO2 concentration, room and supply air temperature and relative humidity, and door opening were measured for four weeks in each classroom. Field inspections identified HVAC equipment, fan control, and/or filter maintenance problems in 51% of the studied classrooms. Across 94 classrooms with valid data, average CO2 concentrations measured during school hours had a mean of 895 ppm and a standard deviation (SD) of 263 ppm. Ventilation rates (VRs), estimated using the daily maximum 15-min CO2 in each classroom, had a mean of 5.2 L/s-person and a SD of 2.0 L/s-person across 94 classrooms. Classrooms with economizers, with or without demand control ventilation (DCV), tended to have lower mean CO2. Improperly selected equipment, lack of commissioning, incorrect fan control settings and maintenance issues (heavily loaded filters) were all associated with under-ventilation in classrooms. Many classrooms in this sample were frequently too warm to support learning. There were 23 out of 103 classrooms that had indoor air temperature above 25.6 degrees C for more than 20% of the school hours. Better oversight on HVAC system installation and commissioning are needed to ensure adequate classroom ventilation. Periodic testing of ventilation systems and/or continuous real-time CO2 monitoring (either as stand-alone monitors or incorporated into thermostats) is recommended to detect and correct ventilation problems.