Could Transparent Wood Become The Way We Build And Heat Our Homes?

With Earth Day taking place this week there's a strong focus on how to build homes that leave as small a carbon footprint as possible. Wood makes a great building material except for one thing—you can't see through it. If you want a window you have to rely on glass, which is expensive and also has a tendency to let in too much cold air. Though researchers at the KTH Royal Institute of Technology in Stockholm have developed a way to chemically treat wood so that it not only becomes opaque—even completely transparent at times—but also stores and releases heat during the course of a day.

The science behind it does not involve Frankenstein-esque maneuvers in a laboratory. Instead the researchers removed the lignin from wood samples, which left plenty of open, porous space inside the still structurally sound pieces of wood (for their research they used silver birch wood). They then filled the empty space with a polymer that matches the wood refractive index so that light would permeate through the sample. To increase its heat storage properties, the team added acrylic and polyethylene glycol, a non-toxic 'phase change material' that goes back and forth from liquid to a solid based on the ambient temperature. As the temperature rises the polymer takes in the increased heat and melts to a liquid (but since it is encased in wood it stays within the cell walls). Once the temperature cools down the heat is released as the polymer becomes solid.

According to Céline Montanari, one of the researchers on the project, one-third of the world's energy consumption comes from the building sector. A large part of that comes from systems to heat, cool and light the building. By creating a way to both increase the amount of natural light and release heat back in to the building as the temperature outside cools down, transparent wood can drastically reduce the energy footprint of a building.

It does go through varying states of opacity as it cools from a liquid to a solid, so it wouldn't be complete replacement for glass windows. It is more applicable to situations that use skylights or as a way to complement the use of traditional glass windows so even more natural light can come in the building. It is also safer than glass since it doesn't shatter on impact, but retains its structural strength due to the tensile properties of cells inside the wood. Montanari gave this talk at a recent American Chemical Society meeting explaining the entire process behind the invention (the photo above is from the talk where she held up her business card, made from this material, and demonstrates how transparent the wood is). The team has already filed a patent and hope to have a viable commercial product several years from now.

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