Evaluation of effect of tree canopy on thermal environment, thermal sensation, and mental state

Greenery is considered an important countermeasure technology that can be used to improve the thermal environment in urban areas. In this study, the effects of environmental factors relating to tree canopies on physiological response and human sensible temperatures were examined. Measurements were analyzed to determine the mutual relationship between the environmental elements of the tree canopy and the physiological response and psychological reaction. In five areas with tree canopies of different forms, located on the Osaka Prefecture University campus, measurements were performed during the hot summer season. The amount of solar radiation in the tree canopy was greatly attenuated in comparison to sunlit locations. In addition, it was determined that the air temperature in the tree canopy was about 1 °C lower in sunlit areas. Human thermal load under the tree canopies is closer to neutral than in sunlit places. The blocking of solar radiation greatly affected physiological response. Results of psychological testing confirm the effect of comfort was experienced under tree canopies. However, gloomy impressions were suffered in areas where the leaf area index was large. The fatigue value correlated best with physiological response. It was concluded that the thermal sensation of hot was causing mental fatigue.