Warmth In Winter: Smart Windows To Let Heat In
November 30, 2011
Lauren Sommer of NPR: Researchers at the window testing facility at Lawrence Berkeley National Laboratory are developing dynamic windows treated with nanocrystals that block heat from the sun when a small electrical current is applied — useful for hot summer days.
When you think of high-tech gadgets that make us greener, you might picture solar panels or electric cars; windows may not seem as exciting. But buildings are responsible for 40 percent of the country’s energy use, and researchers say they can lower that number by making windows smarter.
As someone who studies windows, Howdy Goudey isn’t surprised that most of us find them a little boring.
“It’s a pretty pedestrian object,” he says. “You know, what’s new to do with a window?”
But at Lawrence Berkeley National Laboratory in Berkeley, Calif., windows are the focus of some cutting-edge research in nanocrystal technology.
For the most part, windows aren’t good insulators. They leak heat in the winter and let heat in during the summer. Many homes still have single-pane windows, which were the name of the game during the post-World War II building boom.
Insulating With Low-E Windows
But the country soon learned that insulation is necessary, as energy prices skyrocketed in the 1970s. Double-pane windows became common, and then came double-pane windows with invisible coatings, which are twice as efficient. Today, they make up more than half of windows sold. At a hardware store, these are labeled low-e windows, short for low emissivity.
Goudey demonstrates how the treated double-pane windows work with the help of heat lamps — the kind that diners use to keep food warm.
To simulate a hot summer day, he puts them behind two double-pane windows that look identical. In front of one window, it feels like standing in the sun. But standing in front of the other, low-e window is dramatically cooler, because it has an invisible layer of metal on the glass that acts as an insulator. The coating blocks heat from the sun while letting in light.