Energy Efficiency Research Supports Growing Case for Triple-Pane Windows
The U.S. Department of Energy’s Pacific Northwest National Laboratory in collaboration with a coalition of public and private partners, said in a statement mounting evidence shows triple-pane windows offer a return on investment for their long-term energy savings.
“Lower costs, greater availability, and the drive to reduce carbon emissions are pushing us toward a tipping point where triple-pane windows start making a lot of economic sense,” said Kate Cort, a research economist at PNNL and program manager for ongoing field validation studies of triple-pane windows.
Windows with three panes provide noise dampening, adding quality of life value in residential applications, according to Cort. A new generation of thin triple-pane windows are less expensive and can be more easily retrofitted into existing double-pane frames further adding to their appeal to contractors and property managers.
Triple-pane windows’ two gas-filled spaces provide energy saving insulation. Cort explained that these next-generation windows take advantage of economies of scale provided by the same advanced glass manufacturing technology that churns out thin but durable TV and computer screens.
Over the past three years, Cort and her colleagues evaluated the energy savings and economic factors in an effort to determine how fast triple pane windows will gain widespread acceptance among builders. DOE Building Technologies Office and the Bonneville Power Administration provided support for the ongoing research.
Related Reading: NGA’s energy code consultant, Tom Culp of Birchpoint Consulting answers the question- in a triple glazed insulating unit, is the embodied energy in the added third pane of glass paid back by the extra energy savings realized by the triple glazed unit? Read his analysis and conclusions.
New energy standards create urgency
Another recent study led by Cort, PNNL colleague Edward Louie, and Robert Hart of Lawrence Berkeley National Laboratory showed that for new home construction, triple-pane windows can help builders affordably meet more stringent 2021 energy codes for new homes. Their study, published in the March 2022 issue of ASHRAE Journal showed that when a homebuilder upgrades the windows of a new home from double- to triple-pane, the energy efficiency performance of the windows can improve by at least 40 percent. This added performance boosts the total insulating value of the entire home exterior, often referred to as the building envelope.
“Our study showed that boosting the energy efficiency of windows provides builders with more flexibility in design and the ability to make tradeoffs with other components of the envelope, such as exterior wall insulation, while meeting code,” said Cort.
Triple-pane upgrade price a potential pain point for some builders
Builders play a key role in the adoption of new home building technologies, said Cort. In 2020, she and her colleagues interviewed 29 home builders who have participated in the DOE Zero Energy Ready Home program. They asked builders to explain their decision making process for window selection during the 2018-2019 building season. Forty-one percent of these builders used triple‐pane windows in all their new homes and another 28 percent in most or some of their homes. For those who didn’t use triple-pane windows, the biggest factor was cost.
“The price differential between double-pane and triple-pane windows has been a pain-point for builders,” Cort noted. But she added that the increased incremental material cost of triple-pane windows is now about $700 to $2,400 for a 2,400-square-foot wood-framed home. This is about the same cost as adding an extra inch of rigid wall insulation to the same home.
Some builders also stated that the indirect cost of custom installation for triple-pane windows, which can be 25-50 percent heavier than similar sized double‐pane windows, also weighed into their choice.
“Most builders aren’t familiar with the newer thinner, lighter triple-pane technology,” Cort said, adding that surveys show builders would be willing to try them if the cost and availability made adopting triple-pane materials practical.
