Forest Products Laboratory (FPL) researcher Junyong Zhu in co-collaboration with colleagues from the University of Maryland and University of Colorado, have developed a transparent wood material that may be the window of tomorrow. Researchers found that transparent wood has the potential to outperform glass currently used in construction. ... Heat easily transfers through glass, especially single pane. This amounts to higher energy bills during the colder months when heat escapes and again when heat pours in when it’s warm. Additionally, glass production comes with a heavy carbon footprint. Manufacturing emissions are approximately 25,000 metric tons per year.

Transparent wood, however, has emerged as one of the most promising, translucent materials of the future. Transparent wood is created when balsa wood, one of the lowest density trees in the world due to its fast growth rate, is treated to a room temperature, oxidizing bath that bleaches it of nearly all visibility. The wood is then penetrated with polyvinyl alcohol (PVA), a synthetic polymer, which creates a product that is—like glass—virtually transparent.

Mi, Ruiyu; Li, Tian; Dalgo, Daniel; Chen, Chaoji; Kuang, Yudi; He, Shuaiming; Zhao, Xinpeng; Xie, Weiqi; Gan, Wentao; Zhu, Junyong; Srebric, Jelena; Yang, Ronggui; Hu, Liangbing. 2020. A clear, strong, and thermally insulated transparent wood for energy efficient windows. Advanced Functional Materials. 30(1): 1907511. https://doi.org/10.1002/adfm.201907511.

The energy used for regulating building temperatures accounts for 14% of the primary energy consumed in the U.S. One-quarter of this energy is leaked through ineffcient glass windows in cold weather. The development of transparent composites could potentially provide affordable window materials with enhanced energy efficiency. Transparent wood as a promising material has presented desirable performances in thermal and light management. In this work, the performance of transparent wood is optimized toward an energy efficient window material that possesses the following attributes: 1) high optical transmittance (≈91%), comparable to that of glass; 2) high clarity with low haze (≈15%); 3) high toughness (3.03 MJ m-3) that is 3 orders of magnitude higher than standard glass (0.003 MJ m-3); 4) low thermal conductivity (0.19 W m-1 K-1) that is more than 5 times lower than that of glass. Additionally, the transparent wood is a sustainable material, with low carbon emissions and scaling capabilities due to its compatibility with industry-adopted rotary cutting methods. The scalable, high clarity, transparent wood demonstrated in current work can potentially be employed as energy effcient and sustainable windows for signifcant environmental and economic benefts.

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Keywords: Building materials, wood nanocomposites, thermal insulation, clear, cellulose nanomaterials

Characterization of the transparent wood microstructure
Characterization of the transparent wood microstructure - a) Scanning electron microscopy (SEM) image of the 3D mesoporous balsa wood. Top view SEM images of the b) natural wood and c) delignified wood, showing the thinner wood cell walls after the delignification process. d) Photo of the obtained transparent wood (100 mm × 50 mm × 0.8 mm) with high transmittance and low haze. e,f) SEM images of the polymer-filled transparent wood, showing the dense wood structure. g) Magnified view of the microsized channel walls, in which aligned nanocellulose fibers can be observed. © Forest Service