Field investigation of lifestyle and indoor environment with COVID-19 in facilities for older adults in cold regions of Japan

. The emergence of COVID-19 clusters for older adults has been increasing recently in Japan. Facility staff control cross-ventilation with open windows as the primary measure against COVID-19 in facilities for older adults. In this study, the indoor thermal environment, lifestyle, ventilation method, and other in six facilities for older adults were investigated to understand how facility operation management has changed since the spread of COVID-19. As a result, the indoor air temperature was well-managed in all facilities during both seasons. However, the wet bulb globe temperature was measured above the warning level of 25 °C due to the influence of high indoor humidity in summer. The humidity in the facilities was always controlled under low-humidity conditions during winter. In the lifestyle investigation, many votes suggested that the staff found wearing masks uncomfortable. Most older adults were not wearing masks because it made them feel stuffy. Moreover, the staff opened windows for cross-ventilation without relying on objective judgment. Thus, if effective ventilation is not performed, the ventilation efficiency in the facility deteriorates and raises further infection risks. Therefore, staff in facilities should be maintained appropriate indoor carbon dioxide concentrations by ventilation during the COVID-19 catastrophe.


Introduction
Recently, the number of clusters for older adults caused by COVID-19 has been increasing in Japan. The 2020 report by the Ministry of Health, Labor and Welfare in Japan suggested using the ventilation method to improve closed spaces with poor ventilation in the winter. According to the Building Sanitation Law of Japan standard, a ventilation flow rate of 30 m3/h is recommended as a countermeasure against COVID-19 for buildings. However, realistically it is difficult to introduce outside air through ventilation in facilities for older adults owing to the increased heat shock risk in older adults and for energy conservation. When the risk of infection cannot be sufficiently reduced by ventilation, the indoor environment can be improved using air purifiers and circulators. REAVA (2020) [1] recommended using an air purifier with an airflow rate of 5 m3/h or more. However, the crossventilation effect of opened windows by facility staff with air purifiers and circulators as the main infection control method for COVID-19 is not sufficiently clarified. Kim (2017) [2] and Hayashi (2019) [3] have also highlighted the importance of appropriate ventilation plans and humidification control in the winter in facilities for older adults. However, the indoor thermal environment and lifestyle in facilities for older adults have changed more than ever since the spread of COVID-19. Thus, this study investigates in more detail indoor environment and lifestyle, ventilation methods, and other factors during the COVID-19 catastrophe. * Jinya Takeuchi: jtakeuchi@akita-pu.ac.jp Table 1 shows an outline of the investigated six facilities in the cold regions of Japan. We investigated the indoor thermal environment and lifestyle of older adults in summer and winter. The indoor air temperature, humidity, carbon dioxide concentration, and wet bulb globe temperature (WBGT) in the facilities were measured. Field measurements were conducted in private and shared spaces in each facility. The investigation period in the summer was from August 8, 2019, to September 30, 2019 (F1, F2, and F3). The data collection period in winter was from December 8, 2019, to March 31, 2020 (F1, F2, and F3) and from December 1, 2021, to December 27, 2021 (F4, F5, and F6). We continuously measured the air temperature, humidity, globe temperature, and carbon dioxide concentration at 1.1 m above the floor at 20-minute intervals in two private rooms and one common space at each facility.

Study outline
In addition, the ventilation, HVAC system, and lifestyle of older adults and staff were investigated by an in-person survey and visual check. Moreover, clothing insulation, thermal sensation, and thermal comfort of older adults and staff were examined based on a questionnaire survey and a visual check for a deeper understanding of the indoor thermal environment, measurement, lifestyle, ventilation method, and HAVC system in each facility. Furthermore, the data were collected on factors such as elderly attributes, health conditions, and degree of nursing care.

Facility outlines
All facilities are RC structures; F1-F3 are around 10 or more years old, whereas F4-F6 are relatively new, around two to eight years old. All facilities are equipped with private rooms, but F1 and F3 are mostly multibedrooms. In addition, each facility has a common space where approximately 10 people can have meals and get together. Air conditioners are installed in the entire building in each facility. Additionally, F3-F6 have air conditioners installed in the private room.
Floor heating equipment is installed in each facility's corridors and common spaces except for F6. F3 has an air purifier integrated humidifier, whereas F4 and F5 have a large commercial humidifier. However, F1, F2, and F6 have small portable humidifiers in or near common spaces. Ventilation equipment includes exhaust and supply types and is operated all day at each facility.

Basic attributes of older adults
The average ages of the older adults are 86.9, 87.4, 89.4, 91.6, 90.5, and 83.1 y in facilities F1, F2, F3, F4, F5, and F6, respectively. The ratio of females is high at each facility, and the average level of nursing care required is 4.1, 4.0, 4.4, 4.2, 4.5, and 3.6 at facilities F1-F6, respectively. Thus, compared to the national average of 3.95, the average level of nursing care required at each facility is relatively larger.

Indoor thermal environment
Fig. 1 compares the measured data in the winter with the building sanitation law in each facility. Indoor air temperature is well managed in all facilities in both seasons. However, humidity in each facility needs controlling, considering the low humidity during winter. Particularly, the ratio of relative humidity below 40%, which is the lower limit of relative humidity of the building sanitation law, is 50%, 92%, 91%, 52%, 60%, and 91% at facilities F1, F2, F3, F4, F5, and F6,  respectively. Portable humidifiers are installed in or near common spaces at each facility. However, depending on the ventilation method adopted, such as crossventilation when opening the windows, some facilities experience insufficient humidification. Fig. 2 shows the relationship between outside air temperature and WBGT. In summer, WBGT is measured as the warning level above 25 °C with the influence of high indoor humidity at some facilities. Thus, it is necessary to adequately control indoor air temperature and relative humidity in facilities during summer.

Lifestyle and clothing insulation of older adults and staff
Many older adults require assistance from staff in most facilities and often sit in the same seat. Moreover, since chairs and tables are used for gatherings other than meals, many older adults use them several hours before and after meals. The older adults tend to wear more insulated clothes than the staff. The clothing insulation among the older adults is approximately 1.01 clo thicker than that of staff. Particularly, staff who assist in bathing are lightly dressed, approximately 0.27 clo. However, the caregiver wear light clothing even when doing other work.
While most older adults do not wear masks because it makes them feel stuffy, staff always wear masks except when performing some assistance activities (such as bathing assistance). However, staff report feeling hot and stuffy even when executing clerical or light work. Thus, it is also necessary to observe the thermal sensation and comfort of not only the older adults but also the staff.

Ventilation method and HAVC system
The floor heating and air conditioners are set to 25 °C and 20 °C, respectively, from early morning to night. Only the air conditioners installed in the corridors are operated all day. The doors of the private rooms are kept open so that the heated air reaches each room. If a resident report feeling cold, the staff increases the temperature by 0.5 °C. The common spaces in a facility pose a high risk of COVID-19 infection as they are regularly used by older adults. The ventilation system in common areas is operated with a constant ventilation air flow rate control, with 24-h ventilation (mechanical ventilation system). Fig. 3 shows the relationship between the carbon dioxide concentration and the number of older adults in common spaces. The number of older adults using the common space fluctuates depending on the time of day, i.e., breakfast, lunch, and dinner. Moreover, the occupancy density varies considerably depending on the place of use. Therefore, the required ventilation air flow rate needed for the facility is also fluctuating. However, facility staff open windows for cross-ventilation without relying on objective judgment as the main infection control strategy against COVID-19. As shown in Fig. 3, determining the concentration distribution in the entire space according to usage conditions by measuring the concentration of carbon dioxide using indoor representative points is difficult. Therefore, if effective ventilation is not performed, the ventilation efficiency in the facility deteriorates, raising concerns about further infection risks.

Conclusions
A field investigation was conducted in winter and summer to understand the indoor thermal environment, lifestyle, ventilation method, and HAVC system in facilities for older adults during the COVID-19 catastrophe. The following findings were obtained.
A) Indoor air temperatures and carbon dioxide concentrations are well managed in all facilities in both seasons. However, humidity in each facility is controlled to compensate for the low humidity in winter. In contrast, WBGT in some facilities was measured at the warning level above 25 ℃ with the influence of high indoor humidity in summer. Thus, appropriate control standards should be established in facilities for older adults because, thus far, no control standards for indoor thermal environments exist.
B) Facility staff wear masks all day but reported feeling stuffy. However, most older adults were not wearing masks. For ventilation, facility staff adopt cross-ventilation by opening the windows based on subjective decisions. Thus, it is necessary to not only observe thermal sensation and comfort of the older adults but also the staff.
C) The number of older adults using the common space fluctuates according to the time of day, and the occupancy density varies considerably depending on the place of use. As a result, the required ventilation air flow rate also fluctuates. Thus, if effective ventilation is not performed, the ventilation efficiency in the facility deteriorates and raises further infection risks. Therefore, staff in facility should be maintained appropriate indoor carbon dioxide concentrations by ventilation during the COVID-19 catastrophe.