Thermally modified wood has a low environmental impact and favorable properties, such as enhanced dimensional stability, increased resistance to decay, and often aesthetically desired darker color (through-stained). Yet the lack of uniformity in production methods can cause substantial variations in quality. The industry lacks shared definitions, test methods, and verification pathways – gaps that ultimately hold back wider adaptation. For architects, builders, designers, and consumers, it is important that thermally modified wood consistently meets high quality standards. Therefore, stakeholders in the wood industry should investigate what a common, certifiable framework might look like. The next section examines why standardization has become increasingly important.
In the construction industry and architectural sectors, the sustainability and durability of materials has been a focal point for many and a growing trend of number of years now. This shift in priorities across industries has resulted in moving away from scarce raw materials such as exotic wood species, with experts looking into alternative options.
Rooted in trust, quality, and consistency, the hardwood lumber industry has long thrived on these strengths while adapting to the challenges posed by global demand and regulatory pressures. While buyers, builders and other experts can rely on finding quality raw materials, they have faced a rather fragmented and inconsistent landscape when it comes to thermally modified wood. To compare options effectively, customers need standardized classification systems, consistent test methods, and clear quality benchmarks that foster transparency and expand product knowledge.
While established frameworks such as ThermoWood® have played an important role in advancing thermal modification practices and market acceptance in Europe, the North American market still lacks broadly harmonized standards and certification pathways for thermally modified wood. This creates variations in quality expectations, terminology, and production practices across suppliers and regions.
Jartek’s kiln technologies are capable of producing high-quality thermally modified wood that can also meet the requirements of the ThermoWood® standard when the process is operated accordingly. Building on this foundation, Jartek sees an opportunity to support the development of transparent and process-based certification practices tailored especially for the North American market together with NHLA and industry partners.
Designing thermal modification kilns has always been a highly customized process at Jartek, where the specific needs of each customer are met and the kiln planned accordingly. Our process control technologies allow operators to monitor several process parameters like temperature, moisture and time at each stage of the modification cycle. Creating such data points indicates that the process has been prepared for certification, as defining and controlling variables enables comparison and helps ensure consistent performance.
In the thermal modification process variation between different wood species, thickness of the boards and their initial moisture content play a key role in the outcome. A process-based standard that focuses not only on final product performance - such as dimensional stability and decay resistance - but also on how the wood is stacked, loaded and processed - is therefore something Jartek advocates for.
Convincing buyers requires that they know and understand exactly what they are getting and feel confident specifying thermally modified wood in large-scale projects and international supply chains. Hence, achieving process-based certification is not about limiting creativity but rather unlocking the scalability of wood thermal modification and creating trust among buyers and industry experts alike.
NHLA represents uniformity in the hardwood lumber industry and is committed to education and quality assurance. In the thermal modification of wood, consistency signals quality—and it’s achieved by precisely controlling process parameters from start to finish. Existing grading frameworks supported by NHLA create an opportunity to standardize inputs and as a result achieve more predictable and repeatable outcomes.
Through Jartek’s experience in global markets, and by looking at the success of the NHLA grading system, it is evident that when producers align, it can lead to higher market confidence, better pricing, and stronger international recognition. By working with NHLA and other partners, Jartek aims to support a framework that reflects the lifecycle of the product and its environmental and human impact. To reflect broader building market demands, Jartek aims to build a framework in partnership with NHLA that brings much-needed clarity to wood thermal modification processes.
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