Comfort temperature is important to investigate because the chosen office indoor temperatures affect the energy used in a building, and a thermally comfortable environment makes the occupants be more productive. The effects of temperature on comfort are broadly recognized for thermal comfort. Japanese office buildings are well equipped with air-conditioning systems to improve the thermal comfort of the occupants. The main objectives of this research were to compare the winter comfort temperature in mixed mode (MM) and heating, ventilation and air-conditioning (HVAC) office buildings and to investigate the relationship between the comfort temperature and the indoor air temperature. This study measured the thermal environmental conditions of the office buildings and surveyed the thermal comfort of the occupants. The field survey was conducted during winter in seven office buildings located in the Aichi prefecture of Japan. In total, 4466 subjective votes were collected from 46 occupants. The result suggested that the occupants were found to be more satisfied with the thermal environment of MM buildings than that of HVAC office buildings. Overall, 95% of comfort temperatures were in the range 22~28 °C in MM and HVAC buildings, which were higher than the indoor temperature of 20 °C recommended by the Japanese government. The comfort temperature was highly correlated to the indoor air temperature of the MM buildings than to that of HVAC buildings. This indicated that the occupants were more adapted towards the given thermal environment of MM buildings.

Offices may have different indoor environmental quality related problems, such as space, indoor air quality, office workers’ thermal comfort, productivity, and mental stress. The objective of this study was to examine the effect of indoor plants on physiological/psychological responses and productivity, and to examine the mental healthcare status of office workers. To clarify the effect of indoor plants, we conducted a demonstration experiment in two rooms of an office. The experiment was performed in two office spaces (Office A and Office B) located in Kyoto, Japan. Office A was a call center and Office B was a general office. Subjects were office workers working in one of the above two office spaces. In the experiment, nine cycles were conducted while changing the type of plants including vegetables and foliage plants. A preliminary experiment without plants was conducted as a reference case. Results indicated that plant installations in office spaces have certain mental health‐care effects, namely, relaxation of visual fatigue and the feelings of drowsiness of five groups of work‐related fatigue feelings, and the effects by installations of plants depend on the type of plant and industry, although this study had some limitations because of the demonstration experiment.

According to a survey by the Ministry of Health, Labor and Welfare, the number of mood disorders tends to increase year by year in Japan. Under such a background, from December 2015, it is obliged for employers to perform stress checks of workers once a year. In such a stress society, improvement of office environment is an urgent issue. As is well known, some foliage plants have effects of humidity control and VOC removal from indoor air, improvement of productivity and reducing workers' mental stress as well. In the past, a number of previous studies on indoor plants focusing on these effects have been seen, and most of them were implemented in simulated office spaces in the past. However, recently Iwasaki et al. and Matsumoto et al. have installed some plants in actual office spaces and the psychological effects of plants on office workers are beginning to be considered. The objective of this study is to examine the effect of indoor plants on physiological/psychological responses and productivity, and to demonstrate the mental healthcare for office workers. In order to clarify the effect of indoor plants, we conducted a demonstration experiment in an office. This experiment aims to clarify the effects of indoor plants arranged in workplaces on workers' mental health, such as physiological responses, psychological responses and productivity. The experiment was performed in two rooms (Office A, Office B) in an office on the eighth floor of a building located in Kyoto, Japan. Office A was a call center and Office B was a general office. Subjects were office workers working in one of the above two rooms. Twenty-two healthy people in Office A and 19 healthy people in Office B participated in the experiment. Participants were required to measure physiological responses and answer a Web questionnaire after work once or twice a week. Each office worker worked as usual during the experiment period. The experiment was performed from the end of March 2016 to the beginning of September 2016. In the experiment, nine cycles (one cycle is two weeks) were conducted while changing the type of plants. Plants were arranged in the same amount as possible with a green cover ratio of 10 %. A preliminary experiment without plants was conducted as a reference case. Survey items are divided into four items: indoor environment (temperature, humidity, CO₂ concentration, illuminance, sound level), physiological responses (salivary amylase activity, critical flicker fusion frequency (CFF)), psychological responses (a questionnaire survey through the Web based on SAP and a questionnaire survey “Jikaku-sho shirabe” by which evaluated work-related fatigue feelings and fatigue symptom intensity), and productivity (simple task, calls per hour (CPH)). Indoor environment indices of this study ranged wider than those of the laboratory experiment. The result of evaluating the thermal comfort of each office using PMV showed that Office A was slightly warm, while Office B was neutral. The relaxation effects of plants on visual fatigue were found to be significant in CFF for female when arranging the plants with some petals. Mean score of fatigue symptom intensity showed that foliage plants have a significant effect to reduce the feelings of drowsiness. Effect of the improvement of the productivity using plants installation could not be confirmed in terms of simple task and CPH. Our results suggested that plants installation in office space has some mental healthcare effects, although this study had some limitations because of the demonstration experiment. Some experimental problems related with plants preparation restriction, plants order, a variation of some indoor environment indices, LED lamp lightings are to be solved in the future.

A field survey of indoor environmental measurements and questionnaires on thermal sensation, overall comfort, and behaviors was conducted in four office buildings in Japan by visiting each office every month over a duration of more than a year during the coronavirus disease 2019 (COVID-19) pandemic. The indoor environment was measured concurrently. We obtained 1047 votes from office workers in their 20s to 60s. The regression and Griffiths’ methods were used to calculate the indoor comfort temperature. A logistic regression analysis was used to develop the occupant behavior model. Over 70% of the occupants found the indoor environment comfortable at a mean comfort temperature of 23.2 to 25.9 °C. Gender differences were observed in thermal sensation and overall comfort, but a gender difference was observed only in the cooling mode for the indoor comfort temperature. An adaptive model was developed for the office buildings in Nagasaki city to predict the indoor comfort temperature from the outdoor air temperature. The proportions of heating, cooling, and fan usage can be predicted from the outdoor air temperature using a logistic regression analysis. The adaptive model and occupant behavior model are useful for the indoor temperature control of the existing buildings and thermal simulation of the new building design.

In Japan, the standard of indoor climate in nursery school classrooms has not been established, and the control and maintenance of indoor climate in the classrooms are entrusted to individual childminders. Therefore, indoor climate in nursery school classrooms was measured to prepare fundamental information for proper environmental design and environmental control, considering infants’ comfort and health. The climate of 0-year-old and 1-year-old children’s rooms in 15 nursery schools located in mild climatic areas in Japan were measured in the summer and winter over four years. Consequently, a lower average temperature was found during winter at lower heights at which infants spend time and indoor air quality was found to be poor in both summer and winter due to a lower ventilation rate in some classrooms with a smaller area per infant compared to the minimum standards for child welfare institutions. One classroom with an average CO₂ concentration of over 1500 ppm was found in both summer and winter due to less ventilation. Illumination less than 300 lx in one-third of the studied classrooms and high equivalent noise level in most classrooms were measured. The need for indoor environmental standards was indicated in terms of infants’ comfort and health.

In recent years, it has become a problem that office workers’ stresses affect their intellectual productivity. As one of strategies mitigating the stress while working, many studies on the effect of indoor plants introduced into the office have been conducted. The psychological and physiological effects of indoor plants have been expected to mitigate the office workers’ stresses. Also, the effects of green amenities such as improvement of productivity, control of the indoor thermal environment, relaxation and recovery of visual fatigue, and improvement of air quality have been expected. In this study, a field investigation on the green amenity effects of indoor plants on office workers’ psychological and physiological responses in an actual office was conducted and discussed. This paper describes the measurement results of the physical environment and workers’ psychological and physiological responses under the condition with shelves installed with indoor plants in an office room. It was suggested that indoor plants such as mint, basil and begonia, and a combination of red and green plants were effective for mitigating worker’s stresses.