Transparent wood has been reported in Woodworking Network for years, but now new research has taken the concept a step further. Researchers at the University of Colorado has developed a see-through aerogel made from wood that could replace air in double-glazed windows and make them as insulating as walls. 

New Scientist recently reported on research by Ivan Smalyukh at the University of Colorado Boulder and his colleagues used nanofibres of cellulose to create an aerogel, a solid gel containing pockets of gas, that could function better than air in double glazing.

“We have a very unusual combination of properties, which is a very high transparency aerogel that also has very high thermal insulation,” Smalyukh told New Scientist. “You could think about it as a pillow that keeps heat where you need it and at the same time you can see through it, so you can use it in a window.”

To make the aerogel, researchers suspended cellulose nanofibres from wood in water, then replaced the water with ethanol. Next, they dried the aerogel by raising the temperature and pressure, replacing the ethanol filling pockets in the material with air, then adding silicon compounds to the surface to make it water-repellent, preventing condensation when used in windows. An aerogel filling around 2.5 centimetres wide could make a window as insulating as a wall.

Some of this research started at the Forest Products Laboratory (FPL) at the U.S. Department of Agriculture who developed a transparent wood. As reported in Woodworking Network in 2020, FPL researcher Junyong Zhu developed the material, which the USDA says has the potential to outperform glass in nearly every way.
 
"While glass is the most common material used in window construction it comes with a costly economic and ecological price," writes the FPL. "Heat easily transfers through glass, especially single pane, and amounts to higher energy bills when it escapes during cold weather and pours in when it’s warm."
 
Glass production also creates a heavy carbon footprint, with yearly emissions reaching 25,000 metric tons. 
Transparent wood avoids these negatives.