How Retro-reflective Function Works
Solar Control Window Film Albeedo – What is It?
Solar Control Window Film Albeedo is a revolutionary window film that cuts down on heat both indoors and outdoors. Conventional reflective solar control films keep indoor areas cool by reflecting some of the solar radiation, especially near-infrared rays, to the ground. Near-infrared rays reflected to the ground have a negative impact on the thermal environment of urban spaces（outdoors）, Dexerials decided to develop and market a product that would improve indoor environments without negative effects to the outdoors.
How retro-reflective film works
- Solar radiation
- Near-infrared rays reflected by film
Albeedo IRAVK700 is retro-reflective, it selectively reflects near-infrared rays in solar radiation mostly back toward the sun. A special pyramidal reflective layer (Fig. 1) is embedded in Albeedo, and light entering the structure is reflected multiple times to control the direction in which it is ultimately reflected out. This retro-reflective function was made possible by the combination of Dexerials’ advanced optical design, microfabrication technology, and thin-film deposition technology. The product is formed through multilayered sputtering (laminating with metal and oxide materials) on a structure engineered with nanoscale precision (Fig. 2).
(product number: IRAVK700)
(product number: IRA2J700)
Benefits of Albeedo
Dexerials designed Albeedo for maximum retro-reflectivity during the summer, when the sun’s position is at its highest and sun’s ray strikes the window at a high angle of incidence, in order to provide the interior of the building with heat rejection without negatively impacting the thermal environment of urban spaces. This is why Albeedo is gaining attention as a new technology for mitigating the urban heat-island effect.
Benefits to Urban Thermal Environment Provided by Albeedo
Performance test1｜Ground temperature near glass window
Minimizes temperature rises around the base of buildings
This test to verify the effect of Albeedo improving the thermal environment of streets using part of Tokyo Denki University’s Tokyo Senju Campus Building NO.2.
Three types of glass windows- (1) clear float glass only, (2) window with Albeedo, and (3) window with conventional solar control window film – were prepared for the atrium located on the lower level of the building to examine differences in the temperature of the atrium.
On the afternoon of August 5, 2013, black heat-insulating sheets were placed on the street outside the three types of glass windows to visualize and measure the effects of sunlight reflected downward using a thermography camera.
As a result, while the sunlight reflected by the conventional solar control window film downward heated the black heat-insulating sheets to a temperature of 65℃ or more, the sheets in front of Albeedo film were heated only to a temperature similar to that for the clear float glass. This indicates there were a limited amount of near infrared rays that were reflected downward in comparison with the conventional type.
- *1 Arrows of direct solar reach to heat insulating sheets are omitted on the illustration above.
- *2 Thermal image captured using a thermography camera.
Performance test2｜sol-air temperature
Reduces rises in the temperature felt by people
This test measured sol-air temperatures to examine how film changed the temperature felt outside glass windows. The sol-air temperature is a virtual temperature calculated by adding the effects of solar radiation to the atmospheric temperature and is a temperature indicator close to the sensible temperature. Four types of film were prepared for south facing windows on the first floor of a building: (1)clear flat glass only, (2)a window with Albeedo, (3)window with silver reflective type, solar control window film, and (4)that with transparent solar control window film. A dedicated measuring instrument (SAR meter), covered to block direct sunlight, was installed on the ground at the base of the building to measure the effects of reflected solar radiation.
The sol-air temperature near the window with Albeedo was similar to that for the clear float glass window without film, confirming that the Albeedo decreases the negative effect on the urban thermal environment compared with other solar control window films.
Third-party Verification and Certification
Good Design Award（Japan）2016
Heat Island Institute International,
Technology Award 2017
Ministry of the Environment,
Environmental Technology Verification Program
（Comprehensive Assessment System for Built Environment Efficiency）
Act on Promoting Green Procurement
(Act on Promotion of Procurement of Eco-Friendly Goods and Services by the State and Other Entities)
Projects Albeedo is Employed
Albeedo is in use at these buildings.
Tokyo Denki University, Tokyo Senju Campus (Adachi, Tokyo)
Human Media Creation Center/KYUSYU (Kitakyushu, Fukuoka)
Red-Brick Warehouse (Yokohama, Kanagawa)
Kanda Sakurakan (Chiyoda, Tokyo)