One way to reduce the amount of energy in a building is to regulate solar load. The sun adds heat, which helps warm a home in winter, but isn’t so great in summer.
In the winter, you could open the southern window shades to allow the sun to heat up the home and reduce the load on the heating system. In the summer, you’d have to close those shades to reduce the heating effect of the sun and reduce the need for air conditioning. There are a couple of problems with this, because it means that you have to stay on top of it, opening and closing shades at the right time to regulate solar load. Another problem is that during the day, we need light into order to live and work, so drawing the shades actually increases lighting expenses.
A new film developed by Japan’s National Institute of Advanced Industrial Science and Technology [AIST] doesn’t require any interaction on the part of a person or even a computer system. The new film can even be mounted on existing glass. The film “self-adjusts” and regulates solar load based on the angle of the sun. In the summer, when the sun is high in the sky, the film reflects most of these rays back outside the glass. In the winter, when the sun is low in the sky, the film allows most of these rays to pass through to heat up the building.
The new AIST film makes use of any transparent material’s ability to refract or reflect light based on the angle on incidence. When the angle is closer to perpendicular to the surface of the glass, less than 30°, the light passes through the film, but as the angle gets past 60°, the light reflects off it. In order to keep the view from being distorted, two layers of the film are sandwiched with the oppose angle in between. The new film is simple, requires no electronics or interaction of any kind, and can be installed on existing glass to control the solar load on a building or home based entirely on the season and the angle of the sun.