Field study on indoor air quality in a passive residential building in Chinese severe cold area

A field survey was conducted on indoor air quality in a passive low-energy residential building during the winter of 2017 to 2018 in Harbin. The results showed that the mean indoor air temperature was 25.5°C, and the average relative humidity was 31.3%. The level of CO₂ in passive building (PB) was always lower than the limit of 1000 ppm, indicating a higher air exchange rate in PB. The indoor PM2.5 concentrations in passive households were significantly correlated with the outdoor PM2.5 concentrations but did not vary as much as outdoors. For the clean condition, indoor PM2.5 concentration in PB met the requirement of Chinese standard of no more than 75 μg/m³. For the severe haze polluted condition, the use of a ventilation system with HVAC-filter and enhanced air tightness in PB clearly contributed to lower levels of indoor PM2.5 concentration. Nevertheless, during the outside air polluted period, there was a significant proportion of time with indoor pollution levels exceeding the air quality standard. Therefore, the improvement of filter efficiency is warranted for mechanically ventilated PB.