Key messages The work presented here highlights the importance of building designers and engineers recognising health impacts, as well as energy efficiency and environmental impacts, related to occupant-centric building (c) (d) 200 Indoor PM2.5 concentration Daily mean of indoor PM2.5 concentration Outdoor PM2.5 concentration WHO 24-hour PM2.5 limit 150 100 50 0 30 Temperature (C) (b) 250 25 20 Outdoor temperature Indoor temperature 15 Window status (a) Occupancy stayed within the comfort range all the time. For the auto-window control mode, the peaks of indoor PM2.5 concentration declined significantly with use of the autowindow control, reducing the number of days exceeding the WHO limit of PM2.5 concentration by two from the baseline. Meanwhile, occupant thermal comfort was satisfied. Yet, the results indicated that relying on window controls alone may be insufficient for cases of both high indoor and outdoor pollution levels. In the HAP control mode, the peaks of indoor PM2.5 concentrations were significantly reduced. However, there were still two days when the daily mean concentration of indoor PM2.5 was above the WHO limit, even with the use of HAPs. The reason was that outdoor PM2.5 levels were considerably higher on those days and, therefore, leaving the window open worsened indoor conditions. As shown in Figure 4, for the hybrid control mode which represents the proposed control method the indoor PM2.5 concentration decreased substantially, with no days exceeding the WHO daily limit, while indoor temperature remained within the comfort range. The major advantage of the joint control of HAPs and windows was that the window could be shut when outdoor pollution was high without an accumulation of PM2.5. In this way, the HAP operation was minimised, and the indoor PM2.5 concentration was lowered. Meanwhile, the control algorithm was directed to look for opportunities, when the outdoor air was good, to open the window for natural ventilation. Based on the modelled indoor PM2.5 concentrations of the case-study flat, the mean years of life gained (YLG) for all males in the UK across the modelled period (97 years) were approximately 6.5 million, 15 million, and 18 million for the automatic window/MVHR, HAP, and hybrid modes respectively. The mean YLG for females over the same modelled period were approximately 6 million, 14 million, and 16 million for these three intervention scenarios, respectively (Table 1). The reduction in exposure to PM2.5 from the implementation of the hybrid mode added a mean of nearly six months of life. PM2.5 concentration (g/m) AUTOMATED SYSTEMS Adaptive comfort temperature 1 0 1 0 g Au 22- 6 12 18 Aug 3- 2 6 12 18 Aug 4- 2 12 6 18 Aug 5- 2 6 18 Aug 26- 12 6 12 18 Aug 7- 2 6 12 18 Aug 8- 2 6 12 18 Aug 9- 2 Figure 3 Summer week: Baseline. (a) Indoor and outdoor PM2.5 concentrations with the daily mean of indoor PM2.5 concentration compared with the WHO guideline; (b) indoor, outdoor and adaptive comfort temperatures; (c) window state schedule; (d) occupancy schedule (a) Window Temperature (C) PM2.5 concentration (g/m3) status | 250 200 Indoor PM2.5 concentration Daily mean of indoor PM2.5 concentration Outdoor PM2.5 concentration WHO 24-hour PM2.5 limit 150 100 (b) (c) (d) HAP AIR QUALITY 50 0 30 25 20 Indoor temperature 15 Outdoor temperature Adaptive comfort temperature 1 0 1 0 g Au 22- 6 12 18 Aug 3- 2 6 12 18 Aug 4- 2 12 6 18 Aug 5- 2 6 12 18 Aug 26- 6 12 18 Aug 7- 2 6 12 18 Aug 8- 2 6 12 18 Aug 9- 2 Figure 4 Summer week: Hybrid mode. (a) Indoor and outdoor PM2.5 concentrations with the daily mean of indoor PM2.5 concentration compared with the WHO guideline; (b) indoor, outdoor and adaptive comfort temperatures; (c) window state schedule; (d) HAP operation schedule Control mode Males Females YLG mean Mean days gained YLG mean Mean days gained Auto-window/ MVHR 6,557,926 73 5,948,462 64 HAP 15,209,453 6,557,926 13,739,074 148 Hybrid 17,940,660 199 16,188,821 175 Table 1: Summary of life-table model estimates of changes in mortality from different environmental control strategies based on modelled PM2.5 concentrations in case-study flat design and operation. The implementation of smart building control systems has the potential to reduce peoples exposure to PM2.5 indoors, which could have substantial health benefits. This research adds technical evidence for policy-makers, to help prioritise health in the building sector. It also shows how smart and connected building control systems could improve indoor environments for better health of the occupants. CJ DR ELIZABETH COOPER Lecturer MSc Health, Wellbeing & Sustainable Buildings, UCL DR YAN WANG PhD student at UCL 62 September 2022 www.cibsejournal.com CIBSE Sept 22 pp60-62 Smart air quality control Supp.indd 62 26/08/2022 15:47