Influence of tree shade level on comfort perception - a case study of outdoor public spaces of Viharamahadevi park, Colombo

Abstract

Trees play a vital role in the Sri Lankan context in providing thermal comfort in many outdoor spaces including public parks. But most trees have not been effectively chosen and positioned for public comfort. The research focuses on the impact of sky visibility, through tree canopies, on the perception of comfort for people in outdoor urban public spaces. Viewing the sky has psychological and physical benefits as well as aesthetic appeal. The aim of the research is to find optimum levels of tree shade and sky view that should be provided by trees for human comfort. The study was conducted in Viharamahadevi Park, Colombo. The plant area index (PAI) was used to categorize the tree shade level and was calculated using the software CAN-EYE, based on ‘fish-eye’ lens photographs, together with a perception survey of users. It was found that satisfactory sky view was proportional to the perceived comfort. In the morning, people were comfortable in moderate to high shade (PAI 0.72 to 4.48), but in the evening people were comfortable in slight to moderate shade (PAI -0.93 to 1.07). The discussion will show that a certain level of sky view does not reduce thermal comfort perception and is necessary for better outdoor comfort.