Comparing the Microclimatic Role of Horizontal and Vertical Vegetation to Improving the Thermal Comfort of Outdoor Spaces Between Buildings: A Case study (Faculty of Agriculture, I.K.I University), Qazvin

Vegetation moderates a microclimate by casting shadows, increasing solar reflection and evapotranspiration, and modifying wind patterns. The present study aims to investigate the microclimatic role of vegetated surfaces and structures in improving thermal comfort in outdoor spaces between buildings. The main research question is which green system—horizontal vegetation (green floor) or vertical vegetation (green façade)—is more effective in moderating a microclimate and improving thermal comfort in outdoor spaces? To find the answer, an academic building with vertical and horizontal walls facing an outdoor space (yard) was selected for the case study. Data were analyzed via numerical modeling (ENVI-met) and the RayMan software model. The Indices of PMV (predicted mean vote), PET (physiological equivalent temperature), Tmrt (total mean radiant temperature), and RH (relative humidity) were computed and analyzed to identify and analyze thermal comfort levels in outdoor spaces. The analysis results indicate that vegetation significantly affects thermal comfort in outdoor spaces between buildings in warm seasons by reducing PMV, PET, and Tmrt, while increasing RH. In all analytical models based on the indices of thermal comfort in outdoor spaces, the green floor performed better than the green façade due to a more extensive tree coverage on horizontal surfaces. The trees planted on horizontal surfaces and the ground improve thermal comfort in outdoor spaces by shading and blocking direct sunlight. Further, the results indicate that compared to vegetation, blocking direct solar radiation and providing shading on surfaces are much more effective in improving thermal comfort in outdoor spaces.