If you want to use wood in an exterior application, your options are wider than ever. While durable tropical hardwoods have been decimated by unsustainable logging, there are several methods of preserving wood that produce even more durable and sustainable products. These are not woods infused with toxic chemicals or metal compounds that can leach out. Rather these woods are transformed to be more durable and decay resistant.
Accoya is a treated wood that begins with sustainably sourced softwood such as pine and treats it with a process which makes it an extremely durable and long-lasting wood, even for exterior exposure uses such as siding and decking. Accoya has even been used in a bridge over a highway.
The process used to manufacture Accoya is known as “acetylation.” It uses acetic acid (essentially just strong vinegar) to transform the structure of the wood itself. “The process essentially alters the actual cell structure of wood by transforming free hydroxyl groups into acetyl groups.” This is the part of wood that swells and shrinks with changes in moisture levels, so Accoya is more dimensionally stable than either untreated or conventionally pressure-treated wood.
As the company points out, the process “is entirely non-toxic and introduces no chemicals not already found in the wood.” Like Kebony, another alternative treatment, the wood is highly durable, suited for long-term exposure, and can be cut and worked without needing any additional safety precautions other than those normally used when working with wood.
Accoya offcuts and waste materials can even be ordinarily disposed of or even composted. Plus, Accoya has received a Cradle to Cradle(SM) Gold Certificate for sustainability.
Acetylization modifies the wood all the way through. This means that Accoya can be cut, worked, and shaped without compromising its protection. It’s warranted to last for at least 50 years in above-ground applications and at least 25 years in below-grade or freshwater exposure. Accoya can be used for window and door frames, siding, decking, and even outdoor furniture.
At present, the manufacturing of Accoya is done in Europe, so the transportation of the material makes it less than ideal for North American projects. It’s also more expensive than conventionally treated wood. But the long term savings from not having to maintain and eventually replace the material as frequently can mean it is more cost effective, though the up-front costs may be higher.
Credits: Accsys Technologies PLC.