RETRO-REFLECTING FILM WITH WAVELENGTH-SELECTIVE PROPERTIES AGAINST NEAR-INFRARED SOLAR RADIATION AND IMPROVING EFFECTS OF INDOOR / OUTDOOR THERMAL ENVIRONMENT

We proposed and developed a heat-shielding film that had a similar degree of transparency in the visible range to glass, and in addition had retro-reflective properties in the near infrared range. The film embodies an innovative heat-shielding technique that makes it possible to effectively reflect solar radiation towards the sky while minimizing secondary effects on other buildings and the streets around the buildings. Firstly, we carried out measurements in the urban streets to investigate the impact that heat shielding by high-reflective building envelopes would have on the thermal environment in the neighborhood of the building. The results indicated that solar radiation subjected to mirror reflection from the heat-shielded envelope such as Low-E glass windows would deteriorate the street thermal environment considerably. Secondly, we carried out comprehensive measurements in order to obtain data on the properties of our newly developed retro-reflecting film and carried out measurements in a state in which the developed retro-reflecting film was attached to glass, thereby verifying its optical performance regarding retro-reflectivity and selective transmission/reflection in various wavelengths. On the basis of the obtained results, we made a comprehensive evaluation regarding energy-saving effects, and the impact on an outdoor radiation environment, when the developed retro-reflecting film was applied to office buildings. The result showed that the film proposed herein could reduce adverse effects on an environment outside a building while ensuring the same level of transmission performance and heatshielding performance as that of high-performance glass currently available on the market. It was verified that, with the use of the retro-reflecting heat-shielding film, it would be possible to reduce adverse effects on an outdoor urban environment while reducing energy consumption in a building and enhancing indoor visual and thermal comfort.