In many temperate climates, timber clad buildings, decking, external wooden structures and wooden windows are not just fashionable, they are the norm, In recent years, however, the trend for timber in these applications has spread further afield, including to the Middle East. While timber is not a preferred material for windows in the region, projects going up today are featuring wood in many other applications, such as shade structures, gazebos, bridges, decking and outdoor furniture. In the Gulf, there is now demand for significant volumes of both tropical hardwood species and pressure or chemically- treated softwood species, offering high performance in external applications. However, growing environmental awareness and stricter environmental regulations are forcing developers to look for timber from sources, which have a proven record of sustainable management and low environmental impact. The process of thermal modification (also known as heat treatment) is now able to provide temperate hardwood species with the requisite durability and resistance to decay that was, traditionally, only offered by tropical hardwoods. Whilst the concept is not a new one, thermal modification today is an industrial process, using painstakingly developed technology and it truly represents a new opportunity for American hardwoods.
Thermally-modified hardwoods
The thermal modification process, a clean and energy efficient technology, uses high heat in a controlled atmosphere to improve both the dimensional stability and the decay resistance of wood by permanently altering its chemical and physical properties. By processing wood produced from America's well-managed hardwood forests, thermally-modified US hardwoods provides an affordable and environmentally-friendly alternative to certain hardwoods that might be illegally harvested from endangered tropical rainforests.
The thermal modification process limits the ability of the wood to absorb moisture, so the product is more dimensionally stable and less prone to cup, warp and twist with changes in relative humidity. This increase in dimensional stability significantly extends the service life of applied finishes, reducing maintenance costs. The thermal modification process also removes those nutrients in wood that would otherwise provide a food source for insects and wood-destroying fungi. As a result, the end products do not contain any toxic chemicals to improve longevity and performance.
Opportunities for End Use
Thermal modification opens up tremendous opportunities for manufacturers of wood products. The improved moisture resistance and dimensional stability of thermally-modified hardwoods make them an excellent option for wood flooring in spaces where solid wood flooring has traditionally been ruled out for reasons such as contact with water. Whilst, engineered wood floors have been substituted in many of these areas, strip or plank flooring made from heat-treated hardwood lumber may be a solution to growing the available market for solid wood flooring.
There is also an opportunity for furniture manufacturers to produce wooden outdoor furniture made from thermally-modified hardwoods and offer it as an alternative to traditional species, such as teak. In principle, heat-treated hardwood furniture could be made from lower-cost species, such as ash, red oak, tulipwood and soft maple. While this lower-material cost furniture might not take market share away from teak, it could win significant market share from metal and plastic furniture.
Heat-treated hardwoods also offer the possibility to produce more specialized wood products for those consumers looking for something unique in their homes. For instance, heat-treated wood has been used to replace tiles on a shower floor. In Europe, heat-treated wood has also been commonly used in spas for sauna benches because of its durability and low heat transfer.
Homes with decks, balconies and patios are also potential spaces for heat-treated hardwoods. Composite decking products tend to be commonly specified, however treated softwoods or cedar are also used. Heat-treated hardwoods have the potential to replace both, particularly for those building on the waterfront.
The thermal modification process also sequesters carbon within the wood, giving the end product a rich brown color. The appearance and uniform coloration rival that of many tropical hardwood species and its color alone may be enough to win over end users, as has been the case with numerous furniture manufacturers around the world who are just discovering this material for the first time.
Green credentials
While the use of heat and, therefore, energy consumption may draw criticism from environmentalists, the end product does indeed deliver on the environmental claims it makes. In a comparison between heat-treated lumber and chemically-treated lumber, a recent Life Cycle Assessment conducted in Europe found that the former had about the same carbon impact on the environment as the latter, primarily because thermal modification relies on heat. However, heat-treated lumber is 'greener' than chemically treated lumber because of the lack of chemicals used. Furthermore, in the case of American hardwoods, thermally-modified lumber can be also be positively differentiated in the marketplace due to the long history of good forest governance and management practices in the U.S hardwood industry. Thermally-modified American hardwoods may also be the first truly green lumber resource that performs better and costs less than alternative products developed to replace wood.
Market potential and the future
The potential for thermally-modified American hardwoods is certainly promising, both in established markets as well as in developing ones. Somewhat limited availability may be a constraining factor for the immediate future, but this is changing very quickly, as producers adopt the technology across the United States, Canada and also in Europe and Asia. As the product becomes better known, it is anticipated that its potential as an alternative option in exterior applications or in wet environments will be exploited widely. Its consistent rich brown color, its dimensional stability, resistance to decay and its environmental credentials all point to it being one of the most exciting new products the wood industry has been able to offer in recent years.
© Timber Design & Technology 2013
