Is the design guidance of color and material for urban buildings a good choice in terms of thermal performance?

Cool facades to mitigate urban heat island effects

“…Although the increase in the building reflectivity could significantly lower the air conditioning load in summer, it can lead to an increase in the heating load in winter. 15,21 The impact of high-reflectance building roofs on the annual air conditioning load was found to vary from city to city. According to the data, by applying high-reflectance roofs, the annual air conditioning load would be reduced significantly in cities that are situated in the hot summer/cold winter and hot summer/warm winter regions, but the air conditioning load would be increased in cities that situated in severe cold regions of China (Figure 2).…”

“…The most sensitive material that absorbs and stores heat was bricks, followed by concrete and granite. 26 Hong et al 15 compared the surface temperature of building facades with different materials, the building facades with higher thermal inertia have a lower surface temperature during the daytime and higher surface temperatures at night. According to Figure 1, same amount of short-wave radiation would be absorbed by facades with same reflectance.…”

“…Where Is represents the short-wave incident radiation and α is the facade reflectance, italicϕH is the convective heat exchange between the air and the facade, italicϕL is the long-wave radiation exchange and italicϕst is the heat storage. According to the analysis of Hong, 15 the reflectance, emissivity, thermal inertia of the material and solar radiation received are the factors that can be controlled. Their effects on the thermal behaviour of the building facades are discussed in following sections.…”

“…According to Figure 1, same amount of short-wave radiation would be absorbed by facades with same reflectance. 15 Therefore, the sum of heat stored in building facade and heat released is a constant. For facades with a higher surface temperature during the daytime, more heat would be released to the urban canopy which increase the urban canopy air temperature and lower the outdoor thermal comfort.…”

Study on water cooling island effects under different climatic conditions

“…The process of urbanization is accompanied by the great changes in land use structure and the increase in anthropogenic heat emissions. As a consequence, urban heat island (UHI) effects has become one of the main urban environmental problems (Memon et al 2008;Hong et al 2022b, a). The existence of UHI seriously affects the thermal comfort of residents, increases the energy consumptions and poses a threat to human health (Hong et al 2022b, a).…”