Impact of shading form on campus thermal environment in humid and hot areas
Urban thermal environment is deteriorating due to global warming and heat islands,posing a serious threat to the quality of life and health of residents.Campus is an important type of educational precinct and is also threatened by extreme heat.Improving campus thermal environment and creating a cooler and more liveable campus environment are of significance to secure the health of students and teachers,enrich outdoor activities,improve learning efficiency,and improve energy efficiency.However,microclimatic regulation for a safe,healthy and comfortable built environment is complicated and context-specific.For instance,the regulatory effect of microclimatic parameters on outdoor thermal comfort varies with climatic and geographical conditions.The influence of shading on outdoor thermal environment varies significantly with a specific shading form adopted.Even though,most of the existing studies on shading cooling have focused on a single shading form,and the background climatic and weather conditions of these studies are mostly different,limiting the optimal selection of shading forms due to the lack of effective reference for comparison.In view of this,this study,contextualized in an educational precinct of Chongqing University,explored the influence of different shading forms on campus thermal environments.This paper(1)analyzed the impact of different shading forms on campus thermal environment and compared the outdoor thermal comfort levels in different shaded areas;(2)investigated to what extent the flooring materials and shading forms could affect the campus thermal environment;and(3)investigated the correlation between sky view factor(SVF)and thermal environment parameters,and that between SVF and thermal comfort indices.The area for field experiment is in Area A of Chongqing University.The measurement points were near the playground and around the Democracy Lake.The SVFs of the five measurement points(e.g.A,B,Ctrees,Csun,and D)around the Democracy Lake,with diverse shading forms(i.e.shaded by trees,shaded by pavilions,shaded by trees,shaded by trees,and shaded by trees),were 0.018,0.012,0.014,0.460 and 0.056,respectively.There were four measurement points(e.g.E,F,G,and H)the playground.Such four points were characterized by the same flooring materials,while the shading forms were different such as awnings.The measurement points of E,F,G,and H were shaded by awnings,trees,bare,and bare,so that their SVFs were 0.028,0.101,0.509 and 0.810,respectively.Moreover,the field experiment requires a sunny day to well reveal the outdoor thermal environment and the regulating effect of shading forms.The experiment was conducted from 09:00 to 19:00 on July 26,2021,and the weather during the experiment was sunny and mostly cloudless.The thermal environmental parameters such as black bulb temperature(Tg),air temperature(Ta),relative humidity(Rh),and soil temperature(Ts)were measured in situ.To what extent different shading forms affect outdoor thermal comfort was also analyzed based on two indicators of Physiological Equivalent Temperature(PET)and Universal Thermal Climate Index(UTCI).The results show that(1)Shading could effectively block solar radiation and improve outdoor thermal comfort in summer.Ta,Tg,Ts,PET and UTCI in unshaded spaces were all higher than those in shaded spaces.(2)In hot and humid environments,awning shading and pavilion shading had a better ability to regulate thermal comfort than shade shading.(3)Under shaded conditions,there was no significant difference in the effect of flooring materials on Ta,Rh and outdoor thermal comfort.(4)The SVFs of different shading forms were significantly correlated with outdoor thermal environment,where SVF was more strongly correlated with Tg,Ts,PET and UTCI,and less strongly correlated with Ta and Rh.Accordingly,two suggestions were proposed to improve summertime campus thermal environments.First,shading can effectively improve outdoor thermal environment.Natural shading facilities(e.g.vegetation)and artificial shading facilities(e.g.sunshades,umbrellas,awnings)should be planned and designed to improve campus thermal environments.Artificial shading can be further combined with highly radiant,highly reflective,permeable materials,plant,and water bodies to create a"ground permeable,top reflective"shading system.Natural shading is also dependent on the diurnal and seasonal cooling patterns of vegetation,tree planting area,and tree spacing.Second,a low-reflectivity,highly permeable underlayer is recommended to reduce pedestrian heat stress.Overall,the results of this paper can enhance the understanding of shading and cooling mechanisms on the one hand,and provide theoretical references for architects to design and optimize campus shading systems to enhance the thermal environment and improve outdoor thermal comfort on campuses in hot and humid regions on the other.
shading formcampus thermal environmentphysiological equivalent temperatureuniversal thermal climate index
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