Improving urban green spaces increase thermal comfort of citizens

We are aware that thermal sensation in green areas is reduced, but we cannot precisely specify the effects of its cushioning. A female researcher from School of Architecture at Universidad Politécnica de Madrid has carried out a new model that simulates six different scenarios of green areas and has established the differences among the physiological equivalent temperature on each situation. Results indicate that an increased percentage of green spaces in cities and better landscape design parameters help moderate the urban heat island effect and thus thermal comfort of users.

Esther Higueras, a member of the research group Bioclimatic Architecture in a Sustainable Environment -- ABIO (UPM), has assessed the thermal comfort modification potential of a long belt-shaped park (around 9 km) in Beijing and the effects of its landscape parameters using the ENVI-met© software, a numerical simulation model of surface-plant-air interactions. Beijing was selected because of its humid continental climate affected by monsoons, summer in this city is characterized by torridity and humidity what makes this city a suitable place for many relevant studies of urban microclimate and thermal comfort.

Holistic spatial and temporal distribution scenarios of thermal comfort of the park are obtained in terms of physiological equivalent temperature (PET). This study compared areas of grass, trees of 10 m, trees of 20 m, hardened ground, water bodies and buildings (6 simulations). Green area spaces shown better level of thermal comfort, but there are differences in uncovered areas due to solar radiation and the reflection effect of other surface materials.

The average thermal comfort sensation in green areas range around 2 °C at 2 pm. Regression analyses indicate that the most significant influencing factor on the moderation of thermal comfort is the higher trees, while hardened ground exhibits a negative impact.

This simulation model considered the proportion of each landscape design parameter in the park. However, the model can be valid to improve the conditions of thermal comfort in other parks by modifying those percentages to adjust them to each situation.

Esther Higueras states "the work results provide a detailed knowledge of the real benefits of green areas on the thermal comfort of people." Besides, the researcher adds, "the conclusions allow us to make suggestions to designers of urban parks such as to increase the coverage of taller trees, implement effective approaches in uncovered spaces, reduce the percentage of hardened pavement or to display the landscape parameters taking into account aesthetic aspects that can influence the perceived thermal sensation."