One of the more unusual repercussions from last year’s devastating earthquake and tsunami in Japan may be a change in the way office towers are designed to rely less on electric illumination and more on natural light. A new window glass technology developed over several years by MIT and École Polytechnique Fédérale de Lausanne (EPFL) is now being used in a Tokyo skyscraper to direct daylight as deep as 15 meters into the building’s interior.
Amid concerns about the ability of Japan’s cities to withstand another major power outage like the one experienced after the March 2011 Fukushima nuclear power plant disaster, EPFL’s Interdisciplinary Laboratory of Performance-Integrated Design (LIPID) began working with real estate developer Hulic to retrofit six floors of an existing modern office tower in Tokyo with the new windows. As a result, natural light is being drawn more than twice as far into the building as typical windows, which usually bring light only 6 meters into the interior, thus reducing energy usage.
The key to the technology is the enhancement of reflectivity on the top portion of the windows so that light bounces onto the office ceiling rather than into the eyes of the office workers. The glazing method in these window systems incorporates two materials that help channel the light: 1) an array of horizontal aluminum slats that reduce glare and block rays from pointing downward and 2) a clear acrylic cylinder attached to the slats that acts as a prism to diffuse the light laterally into the room. The top and bottom of the windows include two parabolic curves to catch light and point it toward the ceiling, which is also coated with reflective material to help draw the light farther into the interior.
This patented window system was developed by LIPID chief Marilyne Andersen, who began work on the technology several years ago with the cooperation of Hulic at MIT. This research was then developed further at EPFL before the windows were installed in September.
According to EPFL, most modern office buildings in Japan that have conventional windows function with their blinds closed to prevent glare and use twice as much artificial lighting as European skyscrapers. The hope, EPFL says, is that these windows will help Japanese developers reduce their reliance on electric lighting systems to meet stricter standards.