Researchers from the University of Maryland have found that windows made from transparent wood are more energy-efficient and provide more consistent natural light compared to ordinary window glass.

In a study published in the journal Advanced Energy Materials, Liangbing Hu and colleagues showed that transparent wood offers better thermal insulation while letting in nearly as much light and dispersing light more evenly and consistently without the glare associated with window glass.

This current study builds upon Hu and colleagues' earlier work developing transparent wood.

Transparent wood windows do let in a little bit less light compared to glass but they also let through dramatically less heat. According to Tian Li, the study's lead author, transparent wood is also not completely see-through so it still offers some level of privacy. Additionally, the material features channels that transmit wavelengths around the same range as visible light but block wavelengths that mostly carry heat.

A part of the researchers' findings were based on tests on a small model house fitted with a panel of transparent wood on the ceiling. Based on their observations, light let in by transparent wood is more evenly distributed in a room, making it more comfortable on the eyes.

This is made possible by channels in the transparent wood that direct visible light but bounce around some of the light a bit, resulting in a haze that prevents light from directly shining into the eyes.

It is also because of these channels that light is dispersed more evenly. Typically, light moves in the same direction as the sun. With transparent wood, however, light moves through the material's channels, directed in the same way each time so it doesn't change angles depending on the sun's position.

Transparent wood is still highly similar to natural wood except that the former is waterproof, thanks to its polymer content. It is also less breakable than standard glass because it retains the cell structure of wood, which resists shattering.

To create transparent wood, the researchers start with bleaching the wood to remove lignin, the component responsible for giving wood its color and strength. The material is then soaked in epoxy to make it durable again and make it clearer. For the study, the researchers worked with small pieces of linden wood measuring 2 x 2 centimeters (0.79 x 0.79 inches) but the material can be fashioned into any size.

Alongside Hu and Li, Mingwei Zhu, Bao Yang, Zhi Yang, Glenn Pastel, Jianwei Song, Wei Luo, Jiaqi Dai and Yonggang Yao also contributed to the study.

Photo: Liz West | Flickr

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