Effects of green walls on thermal perception and cognitive performance: An indoor study

Abstract

In this study, 144 university students were recruited to investigate the effects of greenery dosing on emotional and physiological properties by testing neurobehavioral responses, measuring a physiological index, monitoring electroencephalogram signals, and a questionnaire survey. Where there was a non-green wall (green view index (GVI) = 0 %), a small green wall (GVI = 5 %), and a large green wall (GVI = 15 %), the mean thermal comfort vote increased by 0.02, 0.25, and 0.44, respectively, compared to pre-trial conditions. Subjects’ cognitive performance was highly improved in the presence of a large green wall. Systolic blood pressure and heart rate were reduced (1.68 and 3.14, respectively) most significantly in the presence of a large green wall. Diastolic blood pressure decreased significantly by 1.92 in the presence of a small green wall. Oxyhemoglobin saturation and eardrum temperature were not affected by indoor green wall sizes. We found no significant change in the frontal asymmetrical activity of the brain among subjects where there was a non-green wall, but it increased significantly in the event of a small (+0.12) and a large green wall (+0.14). Finally, in a non-green and small green wall conditions, the relative power of δ brain wave activity was minimized and α brain wave activity was maximized 13 and 9 min after the subjects began looking at green walls. After 7 min of exposure to a large green wall, the relative power of δ reached its minimum and α and θ both reached their maximum.