An environmental issue that has emerged in recent years is the heat island effect. What sets cities apart from surrounding areas like islands in the sea is the fact that they are generally warmer, which is caused in part by sunlight reflected to the ground from glass-walled office buildings. To counteract this effect, Sony is conducting R&D on upward heat reflection film, a material that reflects the heat in sunlight back toward the sky.
The 0.2-mm film incorporates a mirrored angular structure as a reflective layer that returns near-infrared rays back toward the sky very efficiently.
Clear enough to let visible light pass through, the 0.2-millimeter-thin film incorporates a layer that selectively reflects back (retroreflects) the infrared rays that make sunlight hot. What's more, we have developed a film structure that retains this special reflective property when the film is wound on a roll, which will facilitate mass production.
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Higher ground temperature from reflected heat
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Reflecting heat back toward the sky counteracts the heat island effect
Upward Heat Reflection Film
Easy to use, the upward heat reflection film can be applied to the glass walls of new or existing buildings.
The technology is promising. Simulations show that applying the film to buildings in the some business district in Tokyo would lower the effective summer temperature by 0.3°C, equivalent to greening an area 10% of the size of the district.