If you catch a member of our research and development team staring out the window in the middle of the day, they aren't just daydreaming. Chances are, they're hard at work finding ways to use transparent aerogel and flexible aerogel blanket insulation to improve the energy efficiency of windows.
Our team, and others, are putting the superior insulating performance of aerogel to work to make more efficient windows, albeit in different ways.
What Makes a Window: The U-Value
The internet is filled with articles describing U-Values (or U-Factors) and what that means for energy efficient windows. You can read one here or here. For the sake of time, we offer our abridged version:
There are two major components of a window: the frame and the glass. To understand the total efficiency of your window unit, called it's U-Value, you need to add together the efficency of those two components.
Uf + Ug = Uw
The Uf value is the measure of the frame's U-Value without the glass. The Ug value is the U-Value of the glass alone. The Uw is the unit's total U-Value.
Obviously, the lower the numbers, the more efficient your window. For heating climates, lower U-Value means less heat loss. You want your window to give you a view, not be a door for heat to escape.
Many window companies work hard to lower the Ug value to create greater efficiency. (For most units, the Ug value is the lowest and best performaing number in the equation.) As a result, you'll see double and triple pane windows that sandwich noble gases, like argon gas, between layers of glass in order to achieve lower overall U-Values. For instance, passive house and low energy structures often rely on triple pane windows to meet stringent efficiency standards. There's even one company working on a 12 pane superwindow. These types of windows work—with a catch.
Not every structure can easily adapt to the thickness, or the weight, of a double or triple pane window unit. Think about heritage buildings that need to maintain their architectural integrity. Tiny homes certainly aren't brimming with space. Even your mid-century modern house would need some major reinforcement to support the weight of the glass in a triple pane window.
So now what?
ARPA-E's Single-pane Highly Insulating Efficient Lucid Designs (SHIELD) program
In 2016, Aspen Aerogels received funding from the U.S. Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E) as part of the SHIELD program. Aspen's team was one of 14 projects selected. The funding is being used to develop a window pane technology that incorporates a transparent, UV-stable silica aerogel layer between two thin transparent sheets of glass to create a double glazed pane.
The 14 SHIELD project teams are working to "develop innovative materials and structures that can more than halve the amount of heat lost through single-pane windows during the winter heating season. These materials and designs would improve a window’s thermal insulation, reduce cold weather condensation, and have a minimal impact on the window’s appearance."
If the project is successful, the aerogel insulated window pane units could be used to replace single panes in windows when the thickness and weight of double pane windows isn't practical.
Looking Beyond the Window Pane
Making better windows with aerogel doesn't stop at the window pane.
Let's look at the U-Value equation again:
Uf + Ug = Uw
If you're already using a system that has a low Ug value, how do you make it better? You focus on improving the Uf value.
Companies like Origin and Aluprof are incorporating Spaceloft® aerogel blanket insulation as part of the window frame to reduce the Uf value. Aluprof uses a patented product called Porofix Profile in their systems supplied by Aerogels Poland Nanotechnology.
In these efficient frames made of wood, aluminum, fiberglass or uPVC, the aerogel insulation is used to fill the voids that would normally be filled with air or even polystyrene. The difference between simply having air in the window frame versus aerogel insulation can make a "14X difference in thermal performance of the window frame" according to one window manufacturer.
So not only does the aerogel blanket insulation help lower the Uf value, it also means the companies don't have to rely on added bulk to achieve U-Values for low energy or passive house grade windows. It makes for slim, lightweight, and very stylish energy efficienct designs.
Side note. You can't have a window (or a door for that matter) without creating a hole in your structure. These openings are most prone to linear thermal bridges. Addressing linear thermal bridges is one of the most popular ways Spaceloft is used; Spaceloft helps increase thermal efficiency, and avoid condensation and mold related problems. It's just another way aerogel insulation is promoting increased thermal comfort in building & construction applications.
Same Material, Different Ways
Remember, if you catch an Aspen Aerogels employee staring out the window, don't assume they aren't hard at work. We're excited for our team and other companies to find new ways to put the superior insulating performance of aerogel to work—for all of us.