Understanding the Difference between Pressure Treated Wood and Acetylated Wood

Especially for home owners, developers or architect when they want to do decking or outdoor structures for their properties, an understanding about wood enhancement method and technology is important. Generally, there is 2 main technology for wood enhancement, Pressure Treatment and Acetylation. Enhancement of wood increase its resistance to insects especially termites and also fungal growth. However, we may need to look beyond these 2 purposes by understanding the differences.

1. Definition and Method of Penetration

Just like painting, for pressure treated timber, chemicals are usually 'painted' onto the timber, put into a chamber, while heavy pressure will try to force the chemicals into the wood.

3 common types of chemicals used in pressure treatment are Chromated Copper Arsenate (CCA), Alkaline Copper Quaternary (ACQ) and Copper Azole (CA). CA method is considered a relatively more recommended method and safer method among the three. 

According to a report by Outdoor Structures Australia, extracting studies from its regulator such as Timber Queensland and National Association of Forest Industries, it is mentioned that "Even in treatable species, Copper Azole will only penetrate (and treat) the Sapwood, but will not penetrate, or improve the properties of, Heartwood."What it means to home owners is that, such treatment is not able to penetrate in the core of the wood (Heartwood).

Also from the report, "The Sapwood of treated timber is protected against attack by termites. However the Heartwood is no more resistant to termite attack after treatment than before" What it means is to the home owners is that treated wood may also be attacked by termites, especially the formidable breed such as the Formosan Termite, due to lack of protection in the heartwood. 

On the other hand,

Acetylation is a complete different technological process from pressure treatment. Unlike traditional pressure treatment, during Acetylation, wood is being scientifically modified completely from the sapwood all the way to the heartwood. During acetylation, the dimensional stability and durability properties of the wood will naturally improve.

Hence Acetylation simply means a modification of wood and not a treatment to the wood. For more information on Acetylation, you can click this article to find out more.

Because of such modification, acetylated becomes naturally highly resistant to fungi as well as insects attacks without any involvement of chemicals. According the test report here, acetylated wood (mentioned as Accoya®) is tested and proven to be highly resistant even to Formosan termites.

 2. Impact on Health

Home owners should always be aware when it comes to the impact on human health risks especially for pressure treatment wood. Out of the 3 common methods of pressure treatment, CA method should be relatively better and safer for the human health because of the lack of arsenic contents. 

Copper Azole (CA-B) contains about 96% of copper and 4% of Azole. Azole is often used in anti-fungal drugs; when treated, the wood will have little to no odor and will also have a greenish brown color. However, there are still different points of view and argument from experts today as to whether CA method is considered safe for the human health or not. A report from the National Centre for Biotechnology Information mentioned that Azole antifungal may impose pregnancy risk on human health; while another report from a chemical manufacturer argued this point, mentioning that only unapplied Copper Azole concentrate could be moderately toxic which may cause harm to aquatic life.

Hence therefore, home owners may need to analyse and weigh the facts before making the decision for the right treatment for their wood. 

On the other hand, wood which is modified by the Acetylating process does not add toxins to the environment and therefore is safe to the human health.

3. Impact on Environment

Treated Wood Waste (TWW) usually comes from old wood that are treated with chemical preservatives. Environmental regulators in some countries such as the California Department of Toxic Substances Control  has warned people not to burn treated wood during disposal as it may cause harmful oxide the environment.  Reports from Tennessee Forest Products Center and Health Canada further emphasized on this issue. This might pose a long term environmental problem of potential landfill wastage should incineration methods are not recommended.

Then, what about for Acetylated wood? 

Wood treated by Acetylation process is non toxic, it can be reused and it is safe to be renewed after disposal. Furthermore, acetylated wood has credible Eco friendly and sustainable standards and accreditations such as FSC, PEFC, Singapore Green Label and Cradle to Cradle certifications.

In a nutshell,

the final say is still up to the home owner as what kind of wood, he or she would like to have for the balcony decks as well as other forms of woodwork construction. Whereas by having a deeper understanding of the different technology of wood enhancement, home owners and building professionals can therefore appreciate the beauty and value of natural wood.