Long-term Monitoring And Analysis On Indoor Air Quality Of Natural Ventilation Residential Buildings In Typical Cities Of Northern China

At present,natural ventilation is the main form of ventilation in Chinese homes.As the air pollution becoming more and more serious,residential indoor air quality in our country have also been affected.The air purifier as a way to fight with indoor PM_2.5pollution is gaining more and more attention among people,but the occupants haven’t got a systematic understanding on operation habits and purification effect of household air purifier.In addition,overheating,especially during the heating seasons,also get public awareness in recent years.Excessive indoor air temperature in heating season will not only lead to energy waste,but also affect the health of the occupants.Reducing indoor pollution and improving indoor thermal comfort should be a priority in building design and renovation.At first,five typical natural ventilation homes in Tianjin have been chosen to have ventilation and purification retrofit.A strategy of using natural ventilation and air puri-fier has been put forward to improve indoor air quality.Multizone network model sim-ulation was carried out to demonstrate the effectiveness of the retrofit strategy.Then long-term monitoring of indoor and outdoor parameters was conducted in the five Tian-jin homes for one year.The results of multizone network model simulation show that by implementing the proposed retrofit strategy,indoor annual PM_2.5 concentration can be kept below 35μg/m³,and the unsatisfaction rate of daily average PM_2.5 concentration and CO₂ concentration can be kept below 10%.The results of long-term monitoring after retrofit show that the natural ventilation dwellings under monitor are well venti-lated,but there is a general problem of insufficient ventilation caused by closed win-dows during night sleep time.After installing air purifiers,indoor annual PM_2.5 concen-tration still exceeded 35μg/m³,which was inconsistent with simulation result.This is due to residents’unreasonable operation behavior of air purifier and window-opening habit.During long-term monitoring in Tianjin,indoor overheating problem in heating season was observed.Therefore,based on the long-term monitoring system,an ex-tended investigation was carried out in four typical cities with central heating system in northern China to study the indoor overheating issue during heating season.Overheat-ing criterions were put forward from two aspects:indoor air temperature and room heat consumption,which are used to evaluate the indoor overheat degree and energy saving potential during heating season.Finally,the overheating degree and energy consump-tion in northern China were discussed.According to the study on overheating during heating season,Shenyang has the highest overheating degree among the others,and the following cities are Urumqi,Tian-jin and Xi’an.Overheating occurs mainly during the day.From the perspective of heat consumption,the indoor overheating degree in daytime is greater than that in the night.And the average heat consumption in daytime is 40%～50%above the theoretical value,while in the night that is 26%～39%.At present,the heating energy saving potential in northern China is 10%～30%.