The greatest challenge to the current generation of buildings is climate change, says a team of researchers from the National Renewable Energy Laboratory (NREL). The researchers write in a paper published in One Earth that if the architectural world wants to continue designing highly glazed buildings, a “transformational glazing technology must emerge.”
Glass buildings account for more than one-third of the world’s energy consumption and around 28% of global carbon emissions. The team writes that if current building trends continue, it is predicted that urban areas will encompass 70% of the world’s population by the middle of this century. While highly glazed buildings offer excellent views, they are costly to cool and damaging to the environment.
“These high levels of energy consumption are in part a result of architectural trends toward poorly insulated glazed façades,” write the researchers. “Window-to-wall ratios have consistently increased since the end of World War II, and demand for highly glazed façades remains high despite wide acknowledgment of their poor energy performance and rising concerns regarding the effects of climate change.”
Though revolutionary window technologies, such as low-E coatings, dynamic tinting, and photovoltaic glass, among others, have been designed and adopted, a “comprehensive understanding of where and how these window technologies can be installed to enable optimal energy savings under different climate conditions remains limited,” write the researchers.
To best understand the energy-guzzling nature of glass buildings, the researchers studied models of thousands of cases, including buildings with a window-to-wall ratio of 95%, to reveal trends that can guide future window technology deployment. What they found was that an average office building can reduce its energy use and associated carbon emissions by more than 40% by using photovoltaic windows along with simple geometric changes.
The team writes that when photovoltaic glazing is integrated into code-compliant double-pane or triple-pane glazing, the amount of energy used is 42% less than substandard windows. They also found that triple-paned windows are successful in reducing energy use.
“A possible improvement of more than 50% is achievable for technologies with efficiencies that are possible but not yet realized,” write the researchers.
The researchers add that while results vary by climate zone, the energy performance of buildings in all locations stands to benefit from next-generation window technologies.
“[Our] work should be a starting point for future building design and motivate a pivot from the focus on improved thermal performance in glazing to photovoltaic generation,” write the researchers. “It is a transition that may be necessary to address impending climate change goals without sacrificing the architectural freedom of highly glazed façades.”