Study on the appropriate selection of urban heat island measure technologies to urban block properties

• The benefit due to a street tree was mainly for the sidewalk.
• The benefit due to a green wall was mainly for the wall surface.
• The benefit due to high reflectance paint and water-retentive pavement was mainly for the roadway.
• The street tree shadows tend to occur on the northern sidewalk of an east–west road rather than on the eastern (western) sidewalk of a north–south road.

In this study, we analyzed the effects of introducing urban heat island measure technologies in a typical street canyon model to aid the selection of a suitable technology. It is appropriate to use street trees for improving the thermal environment of a sidewalk and high reflectance paint or water-retentive pavement for the reduction of surface temperature on the roadway. Reduction of solar radiation gain to the sidewalk pavement surface depends on the location and area of the street tree shadows, which are likely to occur on the northern sidewalk of an east–west road rather than an eastern (or a western) sidewalk of a north–south road. Moreover, the area of the shadow is proportional to the square of the width of tree crown (the radius) and inversely proportional to the distance between trees. Thus, it is necessary to prioritize these considerations based on the road orientation and time when the pedestrian use of sidewalk is the highest.