A new study shows that windows that emit more energy can reduce the amount of CO2 emitted by an average of three times in a year, compared to windows that are energy efficient.
Researchers at Purdue University in West Lafayette, Indiana, analyzed emissions from windows installed in five US states between 2008 and 2013 and found that windows with more energy efficient panels emitted only 1.4 times more CO2 than those with a standard glass panel.
The study was published in the journal Environmental Science & Technology.
Scientists have long known that the efficiency of windows can be enhanced with better energy efficiency.
But the Purdue researchers’ study was the first to analyze emissions from energy efficient window types in a country-wide study.
“This is an area of research that’s been very difficult to conduct,” said senior author Thomas Schramm, a professor in Purdue’s Department of Engineering and Applied Science.
A standard glass window emits around 80 percent of its energy in the form of heat, so it’s important that we know exactly what the energy efficiency of our windows are,” said Schraml, who is also a professor of mechanical engineering and an assistant professor of electrical and computer engineering at Purdue.
If windows are efficient, they save energy and have a reduced carbon footprint, but they also increase the risk of climate change because more CO 2 is released by burning fossil fuels.
Most windows have a carbon footprint that is less than a cubic foot.
This is because the materials used to make windows are more expensive than the energy they consume.
When you think of a glass window, it’s clear you’re looking at something that uses materials that cost millions of dollars to make.
Schramm and his colleagues determined that a typical window made from materials that were roughly 10 times more expensive per unit of energy output than the glass panels it replaced emitted around 15 times more carbon dioxide than a standard window, with an average annual CO2 reduction of about 3.6 percent.
This is the first study to analyze windows made from the same materials as standard windows.
Because of the higher energy efficiency, the researchers believe that the cost savings from replacing a window with a more energy-efficient glass panel would be comparable to the savings of installing a standard LED light bulb, which is less expensive than windows that use less energy.”
If a glass panel were an inexpensive substitute for a standard one, it would save consumers $1.20 per year on energy bills,” said co-author Steven M. Bussard, professor of engineering and director of the Purdue Department of Energy.
For this study, Schrams and his co-authors tested windows in California, New York, Ohio, Pennsylvania and Texas, all with standard glass panels.
The window types tested in each state were rated based on energy efficiency in addition to the efficiency with which they emitted CO2.
In California, standard windows were rated for the efficiency at which they produced the equivalent of around 5 percent of their energy in CO2 by using an energy efficient fluorescent light bulb.
Light bulbs emit CO2 when they burn.
Standard glass windows emit CO02 when they absorb CO2 from the air.
LED light bulbs emit less CO2, but emit more CO from their photovoltaic panels, so they are more energy intensive to produce.
As a result, standard glass windows were evaluated as having higher energy efficiencies than standard LED windows.”
These results demonstrate that standard glass and LED window types can both be efficient and produce CO2 reductions of 3.5 percent when compared to standard glass,” said Bussards co-lead author, Jennifer M. Ritz, a postdoctoral researcher in Schramms lab.
It’s not clear if the window efficiency would increase if more energy were available from the light bulb or the photovolcanics, but Schram’s team thinks that if the light bulbs were more energy dense, they would be more efficient.
The researchers are also looking at window types with lower energy efficiency and how much energy they could use to produce the same amount of energy with a less efficient design.
The study’s results suggest that standard windows with higher energy-efficiency windows may be more energy friendly than standard windows without the extra energy efficiency that comes with more efficient windows.
The study also found that the higher efficiency of standard windows reduces the impact of other greenhouse gases such as carbon monoxide and nitrogen oxides.
