Move over glass windows, something even more old school than you could be back in fashion. A new paper in Advanced Energy Materials
finds that windows made of transparent wood could provide better energy efficiency than glass, while eliminating glare and providing uniform and consistent indoor lighting.  

The process starts with bleaching from the wood all of the lignin, which is a component in the wood that makes it both brown and strong. The wood is then soaked in epoxy, which adds strength back in and also makes the wood clearer. The team has used tiny squares of linden wood about 2 cm x 2 cm, but the wood can be any size, the researchers said.

The paper revealed tests on tiny model house with a transparent wood panel in the ceiling that the team built. The tests showed that the light was more evenly distributed around a space with a transparent wood roof than a glass roof. The channels in the wood direct visible light straight through the material, but the cell structure that still remains bounces the light around just a little bit, a property called haze. This means the light does not shine directly into your eyes, making it more comfortable to look at. And working with transparent wood is similar to working with natural wood, but the transparent wood is waterproof due to its polymer component. It also is much less breakable than glass because the cell structure inside resists shattering. 

Transparent wood still has all the cell structures that comprised the original piece of wood. The wood is cut against the grain, so that the channels that drew water and nutrients up from the roots lie along the shortest dimension of the window. The new transparent wood uses theses natural channels in wood to guide the sunlight through the wood.

As the sun passes over a house with glass windows, the angle at which light shines through the glass changes as the sun moves. With windows or panels made of transparent wood instead of glass, as the sun moves across the sky, the channels in the wood direct the sunlight in the same way every time.

"This means your cat would not have to get up out of its nice patch of sunlight every few minutes and move over," said Tian Li, the lead author of the new study from the University of Maryland. "The sunlight would stay in the same place. Also, the room would be more equally lighted at all times."

The research team has recently patented their process.

Citation: Tian Li and Mingwei Xu, et al., “Wood Composite as an Energy Efficient Building Material: Guided Sunlight Transmittance and Effective Thermal Insulation”, 

Advanced Energy Materials, 2016 DOI:10.1002/aenm.201601122