Recently, windows with low-e double-glazing or heat-shading films often have been installed to the exterior surfaces of buildings to reduce the cooling load of the buildings. These windows specularly reflect solar radiation into pedestrian spaces. It has been pointed out that the increase in the incident solar radiation reflected at the windows degrades the thermal comfort levels of pedestrians. The installation of near-infrared rays retro-reflective film to window surfaces may both reduce the cooling load of the building and reduce the impacts on the thermal environment in outdoor spaces. Hence, it is expected that the installation of this film will counteract this problem and have positive effects. To assess the feasibility of installing retro-reflective materials to the exterior surfaces of the building walls and ground forming part of a city block, for improving the thermal environment in outdoor spaces, computational methods could serve as a powerful tool for analyzing the radiant environment in urban and building spaces. In this paper, a computational method is outlined for considering the directional reflections from the exterior surfaces of building walls and windows. The method is used to estimate the effects on the outdoor thermal comfort of pedestrians in the summer season.