Reduced / Sequestered
(To Implement Solution)
A one-time luxury, glass windows are now standard across the world, bringing light and visibility into the built environment without inviting in the weather. Except windows do let in the weather, in the form of heat or cold. They are much less efficient than insulated walls at keeping room temperature in and outside temperature out—by a factor of 10 or more.
Various measures can improve a window’s efficiency: layered panes, reflective low-emissivity coatings, insulating gas between panes, and tightly sealed frames. More adaptive technologies, dubbed “smart glass,” make windows responsive in real time to sunlight and weather, reducing a building’s energy load for lighting and improving heating and cooling efficiency.
Smart glass relies on chromism, the term for any process that causes material to change color. Electricity triggers it in electrochromic glass: When exposed to a brief burst of voltage, ions move into another layer of glass and the tint and reflectiveness change. Thermochromic glass is triggered by heat: Based on outside temperature, it transitions automatically from transparent to opaque and back again. Photochromic windows operate similarly, on the basis of light exposure. Currently challenged by cost, smart glass will become much more common in the coming decades.
Dynamic or “smart” glass is an up-and-coming solution with a current adoption of only 0.5 percent of commercial building space in the high-income countries. We assume that growth will occur primarily in the commercial sector in high-income countries which already see high adoptions of static high-performance glass. We assume that dynamic glass can reach 30–50 percent of commercial building space in the high-income by 2050. The potential climate-weighted energy efficiency from cooling is estimated at 9 percent and lighting at 9 percent. Both will vary depending on local climate and building location and orientation. Adopting dynamic glass can result in 0.3–0.5 gigatons of emissions reductions from decreased energy use. The additional financial cost is US$69–103 billion, yielding lifetime operating savings of US$99–165 billion.