The natural graying effects of Thermally Modified Wood does it effect its durability?
The short answer is no but lets read further. For most of us we have all experienced the appearance of a natural wood product after it has been exposed to the ultraviolet rays of natural sunlight over a period of time. Its cause is largely due to dust, pollen, dirt, and air pollutants replacing the exposed colored cells of the wood. While there is currently no exterior natural or artificial wood that won’t fade when exposure to UV, thermally modified wood seems to fade more quickly than other natural wood species.
Why? When wood is thermally modified it reduces the woods ability to fade over longer periods of time due to the fact that during the thermal modification process the alteration of the woods lignin in combination with the removal of the woods sugars and natural resins allows the ultraviolet rays to begin altering the woods surface appearance by graying quicker than non thermally modified woods.
In no way does the graying of thermally modified wood effect the overall performance of the woods ability to remain structurally sound for longer periods of time compared to other wood species when exposed to the outdoor elements. Thermally modified wood is wood that has been subjected to heat and steam done in a controlled environment lacking any oxygen. The results of which if properly done makes the wood impervious to rot and mold and provides the wood with a much greater dimensional stability.
The cost of thermally modified wood available in a hardwood such as Ash are above average per square foot over species like Western Red Cedar and Ipe but making a comparison strictly on the merits of price can often times be misleading. Thermally modified wood is in the top 5% of the Class 1 durability rating. The natural durability rating of a species is a rating of the woods natural resistance to attack by wood destroying fungi and wood destroying insects. While species such as Ipe and Western Red Cedar are naturally durable, thermally modified wood due to the man made process of thermal modification in a controlled environment receives a higher durability rating than either of these species.
Other considerations to cost go against Ipe as its hardness often makes installation of decking and siding labor intensive with special cutting tools and longer installation times resulting in higher labor costs. In recent years we have seen a steady decline in Western Red Cedar’s board grade due in large part to the harvesting of smaller diameter trees which have more limbs per foot increasing the number of knots and reducing the amount of defect free wood.
Thermally modified wood has started to find its place as a viable alternative to other wood species here in North America. Its not perfect but if you take the time to research the product and the companies that know how to properly thermally modify you can start to see its distinct benefits over traditional non thermally modified woods. A strong brand in Europe called Novathermowood manufactured by Novawood is a well recognized company around the world for its advanced technology utilized in the thermal modification process.