As the popularity of wood-based materials in building construction increases, facade-based applications are becoming more desirable and prevalent. Wood’s susceptibility to decay is a familiar phenomenon, and many established preservation methods exist. However, most wood treatments for external use are problematic from human health and environmental perspectives.
Conventional preservation chemicals include chromated copper arsenate (CCA), creosote, pentachlorophenol (PCP), alkaline copper quaternary (ACQ), and copper azole (CA)—compounds that contain known hazards. For example, CCA includes arsenic, which is a known carcinogen, and PCP has been associated with immune system suppression and neurological degradation. Copper-based chemicals like ACQ and CA also readily corrode metal fasteners, and some coatings can leach out of the wood under particular environmental conditions. For these reasons, scientists and manufacturers have been developing alternative techniques that are biocompatible and ecologically friendly, aiming to preserve wood effectively without the drawbacks of harmful chemicals.
Leonid Furmansky
The Vibrant restaurant, designed by Schaum Architects, in Houston's Memorial Park, was built, in part, using Accoya tongue and groove exterior cladding.
One established innovation is acetylation, a chemical modification process that enhances wood’s dimensional stability and resistance to biological degradation. In simple terms, the wood is treated with acetic anhydride—a vinegar-like, toxic substance that, after curing, leaves no harmful residue in the final product. This process does not turn softwood into hardwood, nor does it create a surface barrier against water. Instead, it alters the wood at the cellular level by reducing water-attracting hydroxyl groups and increasing naturally occurring acetyl groups. The result is a highly durable, long-lasting material that maintains its shape and resists rot—outperforming most traditional hardwoods in exterior use.
Accoya, the leading manufacturer of acetylated wood, offers products with impressive durability and sustainability credentials. Its acetylated wood comes with a 50-year warranty in above-ground applications and a 25-year warranty for use in freshwater or in-ground conditions. Accoya Wood Siding can now be used in WUI-designated areas
Researchers at Aalto University are currently developing techniques to optimize acetylated wood performance under high-temperature processing, such as hot-pressing, which can typically promote moisture uptake.
FLorida Atlantic University Engineers fortify wood with nano-iron. A microCT image shows the distribution of the iron mineral in the wood cell wall (in turquoise).
A Florida Atlantic University research team has developed a method to elevate the mechanical performance of hardwood as well. The technique strengthens the cell walls of trees by introducing an iron compound into their vascular systems. Ferrihydrite, a naturally occurring ferric nitrate and potassium hydroxide mineral, increases the material’s durability without much additional weight. “To test our hypothesis—that adding tiny mineral crystals to the cell walls would strengthen them—we employed several types of mechanical testing at both the nanoscale and the macroscopic scale,” explains FAU biomedical engineer Vivian Merk. Merk and her team imagine that such mineral enhancement methods could make wood more comparable to concrete and steel in building structure applications.
The work of Lili Cai, Ph.D., assistant professor of forest & sustainable products, paves the way for greener building practices by turning waste into sustainable solutions for wood preservation
Lili Cai, a wood scientist at the University of Idaho, has devised various novel wood preservation techniques at the institution’s Department of Forest, Rangeland and Fire Sciences. One method involves combining zinc oxide with essential oils to create a cement-like compound that is stronger than the wood itself. The zinc-based coating protects wood from fire as well as rot. Other approaches include the use of food waste. Discarded potato-based foodstuffs, such as potato peels and potato chips, can be used to make biocompatible protective materials for wood.
Legume-based foodstuffs like soybeans and lentils contain high quantities of phytic acid, which performs well as a fire retardant. Scientists like Cai focus on the use of wood materials in construction and emphasize the ecological importance of material preservation advances. “If you can extend the life of those wood materials, you can potentially help with climate change,” she explains.
Improving the sustainability of wooden buildings (KyotoU / Whitney Hubbell).
Other investigations seek to prevent decay before it begins. Research by Kyoto University scientists reveals that wood deterioration begins in undetectable ways and often causes measurable damage before it is visible to the naked eye. The team has devised a new technique to detect the early warning signs of wood decay. “If we can ‘see’ what the eye cannot, we can extend the life of wooden structures and improve sustainability in the building industry,” says author Yoshikuni Teramoto. The method combines mid-infrared spectroscopy with artificial intelligence, and machine vision and learning analyze small chemical changes to diagnose the initial signs of deterioration. The proactive strategy shifts protection from reactive preservation to predictive maintenance, enhancing the longevity of wood surfaces.
