As North American industry organizations continue discussions about standards and certification requirements for thermally modified wood, a comprehensive study conducted by the Natural Resources Research Institute (NRRI) offers data that may help inform the process.
Completed in 2021 but largely unnoticed outside a very limited group of stakeholders, the NRRI study evaluated thermally modified Eastern hemlock, balsam fir, white ash, red maple and yellow poplar using American Wood Protection Association (AWPA) test methods and North American wood species.
This makes the study unusual within the thermal modification sector, where much of the published performance data is based on European species tested according to European standards.
The research investigated wood modified using the Moldrup-TMT process, a Closed Wet System (CWS) technology. The results demonstrated significant improvements in moisture resistance, dimensional stability and biological durability, while also documenting the mechanical property changes that designers and specifiers must consider.
Particularly noteworthy was the durability performance of Eastern hemlock, balsam fir and white ash. According to the NRRI researchers, these species showed potential to meet AWPA performance thresholds for above-ground exterior applications, including cladding, windows, doors, millwork and other building components.
The study also included long-term outdoor exposure testing in Hilo, Hawaii, one of the most aggressive natural decay environments used for wood durability evaluation.
“Industry discussions regarding future certification frameworks are important and necessary,” said Bror MOLDRUP, COO at IWT-Moldrup. “At the same time, comprehensive AWPA-based performance data already exists for several North American species. The NRRI study provides a valuable technical reference as those discussions continue.”
As the industry works toward greater standardization, the NRRI report remains one of the most extensive publicly available evaluations combining North American wood species, AWPA test methods and a commercial-scale thermal modification process.
For additional information about the NRRI study and Moldrup-TMT technology in the North America, visit www.americanwoodtechnology.com
