Construction Corner: Windows made of…transparent wood?

A lot of research time and money has been spent on windows. As a result, a simple-looking window can be a pretty sophisticated element in a building’s skin.

There are double- and triple-glazed windows, designed to reduce heat loss while admitting light. There are double-glazed gas-filled windows. There are switchable windows that darken at the touch of a switch, sort of like a building putting on its sunglasses.

But scientists are still working at ways to make windows that transfer less heat while maintaining transparency.

Now researchers at the University of Maryland have come up with a method that they say will do that. They say their technique could provide more even and consistent lighting and better energy efficiency than glass.

Instead of using glass, they’re using transparent… wood?

Yep. Wood.

Their research has been published in the journal Advanced Energy Materials.

They say their transparent wood provides better thermal insulation and lets in nearly as much light as glass, while eliminating glare and providing uniform and consistent indoor lighting.

The lead author of the paper, Tian Li, says, "The transparent wood lets through just a little bit less light than glass, but a lot less heat."

"It is very transparent, but still allows for a little bit of privacy because it is not completely see-through."

But, yes, you can see through it. The question is how does one make wood transparent?

The process starts by removing the lignin from the wood. Lignin is the substance that gives wood both colour and strength. It plays a crucial role in conducting water via channels within the trunk up through the tree and out into its limbs.

After the lignin is removed, the channels it occupied remain, but weakened without lignin’s support. So at that point the wood is soaked in epoxy, which adds strength back into the wood, and helps make the wood clearer.

To make a transparent pane the wood is cut so the channels in it lie more or less horizontal. As the sun moves across the sky, the angle at which the light strikes windows is constantly changing.

With glass windows, the sunlit interior of the building moves with the sun. But with windows of transparent wood, the angle of the sunlight shining on the house changes, but the channels in the wood direct the light into the interior in the same direction every time. You can’t watch a sunbeam move slowly across the floor.

"It means your cat wouldn’t have to get up out of its nice patch of sunlight every few minutes and move over," Li said. "The sunlight would stay in the same place." And the room would be more equally lit all day.

During its research, the team also learned that the channels in the wood transmit light with wavelengths in about the range as the wavelengths of visible light, Li says, "but it blocks the wavelengths that carry mostly heat."

To conduct some of the research, the team built a tiny model house with a transparent wood panel in the roof. And they were able to show that the light was more evenly distributed around a space with a transparent wood roof than a glass roof.

Working with transparent wood is much like working with natural wood, the scientists say. But the transparent wood is waterproof because of its polymer component. And the cell structure of the material resists shattering, so the wood is much less likely to break than glass.

The team has already patented its process it used for making transparent wood, but that doesn’t mean it will be on the market any time soon. We don’t yet know whether the process can be scaled up successfully for mass production. Nor do we know the price. But wooden windows are unquestionably an intriguing idea.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com.