BRAND-NEW
Researchers Developed a Nanoscale Window Coating That Reduces Energy Costs The nanoscale technology could elevate the thermal performance of single-pane windows to that of double-pane.
R
esearchers from the Penn
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Then, by testing a single-pane window
State University have recently
coated with the nanoparticles under
developed a nanoscale
simulated sunlight in the laboratory,
technology that could help to elevate
the researchers confirmed the
the thermal performance of single-
predictions that had been made by
pane windows to that of double-pane
the simulation: there was a significant
windows in winter.
rise in temperature on the side of the
By sandwiching a layer of insulating air,
window coated with the nanoparticles,
double-pane windows allow to improve
indicating that the coating could pull
energy efficiency over single-pane
heat from the sunlight inside, in order
windows, although replacing them can
to compensate for internal heat lost
be expensive or technically challenging.
through a single-pane window.
A more economical but less effective
The researchers then implemented
alternative would be to coat single-pane
their data into a larger-scale simulation
windows with translucent metallic films
to analyse the energy savings for an
capable of absorbing some solar heat in
entire building with coated windows
winter without compromising clarity of the glass. However, the solution
across different climates. Compared to a commercially available
developed by the researchers may now improve the coating’s efficacy.
single-pane window’s low-emissivity coating, the photothermal coating
“Near-infrared light — a portion of solar light that humans cannot see
absorbed much of the light in the near-infrared region of the spectrum
but can feel as heat — can activate unique light-to-heat effects on
while the conventionally coated window reflected it outside. This near-
certain metallic nanoparticles, enhancing how heat flows inward through
infrared absorption resulted in a roughly 12% to 20% reduction in heat
a window. We were interested in understanding how these effects
loss compared to the other coatings and an overall building energy
could be helpful in saving energy in buildings, particularly during the
saving potential of up to around 20% when compared to a building with
winter season,” stated Julian Wang, associate professor of architectural
no coatings on single-pane windows.
engineering and affiliated with the College of Art and Architecture’s
To account for seasonal changes, the researchers also implemented
Department of Architecture and the Materials Research Institute at Penn
awnings into their building-scale simulation, blocking the more direct
State.
rays of sunlight that heat the environment in summer, largely negating
The study
the undesirable heat transfer and any associated cooling costs. “As demonstrated by this study, we can still improve the overall thermal
The research team first developed a model to estimate how much
performance of single-pane windows to be similar to double-pane
heat from sunlight would be reflected, absorbed into or transferred
windows in the winter season at this research stage. These findings
through a window coated with metallic nanoparticles. They selected
challenge our conventional solution of using more layers or insulation
the photothermal compound because of its ability to absorb the sun’s
materials to retrofit single-pane windows for energy savings,” added
near-infrared light while allowing for ample visible light transmission at
Wang.
the same time. The model predicted that the coating would reflect less near-infrared light or heat, absorbing more of it through the window
For further information: www.psu.edu/news/
than most of other coating types.
international PAINT&COATING magazine - JANUARY/FEBRUARY 2022 - N. 73
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