Highly Reflective Roofing Sheets Installed on a School Building to Mitigate the Urban Heat Island Effect in Osaka

Abstract

Abstract:Currently, strategies to mitigate urban heat island (UHI) effects and reduce building energy consumption are implemented worldwide. In Japan, as an effective means of mitigating UHI effects and saving energy of buildings, highly reflective (HR) roofs have increasingly been used. In this study, in order to evaluate the effect of HR roofs on building energy conservation, we investigated the solar reflectivity of a subject school roof in Osaka, Japan, in which HR roofing sheets were installed on the roof from 2010. Additionally, monthly and annual thermal loads, including the cooling load and heating load of the top floor of the school, were calculated using the thermal load calculation software New HASP/ACLD-β. Comparing the calculated thermal loads of the school after HR roofing sheet installation to before, the annual thermal load decreased about 25 MJ/m 2 /year, and the cooling load decreased about 112 MJ/m 2 /year. However, the heating load increased about 87 MJ/m 2 /year in winter. To minimize the annual thermal load, thermal insulation of the roof was also considered to be used together with HR roofing sheets. Thermal load calculations showed that the combination of HR roofing sheets and thermal insulation can be effective in further reducing the annual thermal load.

Temporal Effects of Environmental Characteristics on Urban Air Temperature: The Influence of the Sky View Factor

“…Thus, research on the relationships between urban temperature and built environments has been conducted to help mitigate urban heat. Most previous studies have concentrated on aspects of built environments such as land cover, impervious surfaces, normalized difference vegetation index (NDVI), normalized difference built-up index (NDBI), albedo, building footprints, land uses, building roofs, and open spaces [6][7][8][9][10][11], and they have reported consistent results on those indices. Generally, increases in impervious surfaces, NDBI, and building footprints lead to higher urban temperatures, whereas increases in NDVI, albedo, and parks and open spaces mitigate the intensity of UHIs.…”

Effect of highly reflective building envelopes on outdoor environment temperature and indoor thermal loads using CFD and numerical analysis

“…The urban heat island (UHI) effect is a well-documented climatic change phenomenon and is becoming very serious especially in the summer period due to the rapid increase of urban anthropogenic heat [1]. It was reported that the UHI intensity in hot climates may raise temperatures by 10 o C [2], resulting in increased discomfort and higher pollution levels, while it has a serious impact on the cooling energy consumption of buildings [3,4]. In order to mitigate the UHI effect, many studies have focused on defining the relationship between rising temperatures and different urban elements [5][6][7].…”

Is High Urban Landscaping or High Urban Albedo More Effective for Urban Heat Island Mitigation? : Simulation Analysis on Effects of Urban Landscaping and High Albedo Envelope on Urban Microclimate in Osaka

“…The urban heat island (UHI) effect is a well-documented climatic change phenomenon and is becoming very serious especially in the summer period due to the rapid increase of urban anthropogenic heat [1]. UHI intensity in hot climates may raise temperatures by 10 o C [2], resulting in increased discomfort and higher pollution levels, while it has a serious impact on the cooling energy consumption of buildings [3,4]. In order to mitigate the UHI effect, many studies have focused on defining the relationship between rising temperatures and different urban elements [5][6][7].…”