It has been suggested that the reuse of H2F framing at the end of a building’s life may pose a substantial problem in 20-30 years. This article explains the nature and benefits of H2F framing, why the suggested timeline is too short and why the magnitude of the problem has been over-estimated.
H2F treated framing, easily recognised by the distinctive blue colouring, was developed to prevent termite attack, a potential problem in improperly constructed buildings in some areas of Australia.
It has long been recognised that it is far less expensive to exclude termites than control them and complete repairs once they infest a structure. Once they have entered, termites can not only damage timber, including framing, joinery and furniture, but will eat other cellulose-based materials, even the paper covering on plasterboard.
The traditional approach to termite protection was to create a chemical barrier, drenching the soil with a long-lasting insecticide (chlordane was a major one). Houses were also built with exposed surfaces so any termite attempts at access (e.g. mud-tubes) could be easily detected. Mechanical barriers, such as mesh, are also used to prevent termite ingress.
Today, many of the long-lasting soil poisons are no longer available and those that are provide reduced periods of protection, often less than 10 years, and need to be reapplied to continue to protect the building.
The softwoods which are used for most timber framing in Australia, are not naturally termite resistant. The H2F process coats the dry timber with a thin layer of an insecticide, with added blue colouring to make it easily recognisable on the job site.
The H2F treatment uses one of three insecticides: bifenthrin, permethrin or imidacloprid. Permethrin (which is widely used to treat scabies and lice on humans) and bifenthrin are pyrethroids, which are related to natural products found in chrysanthemums. Imidacloprid is a neonicotinoid, which is related to the nicotine found in tobacco.
All are effective at very low levels, have exceptionally low toxicity to humans and repel termites, providing protection for the life of the structure, typically 50 years or more. Retrofitted houses that retain the H2F treated timber frame and update other features will continue to benefit from its protection. Many currently occupied timber framed homes in Australia were built in the 1800’s.
It has been suggested that the disposal of H2F framing at the end of a building’s life may pose a problem. At present, there are few economical pathways for disposal of any framing timber other than landfill or composting. This situation can be expected to change as the market embraces and applies the concept of a circular economy in which there is a much greater focus on the retrieval and reuse of materials.
The Centre for Timber Durability and Design Life at the University of the Sunshine Coast is currently working on ways to improve the reuse of timber, while the timber industry is looking to identify national approaches to recovery and reuse that avoids landfills.
H2F framing was introduced relatively recently, so at the moment there is very little entering the waste stream.
However, for the H2F treated timber that does enter the waste stream It is important to consider the amounts of chemical in these timbers and the risks they pose as well as the relative rates of degradation in a typical municipal solid waste facility.
The Australian Standards (AS/NZS-1604) for H2F treatment specify slightly different amounts for each of the three chemicals to slightly different depths in the timber.
The amounts of any one of the three chemicals in the timber is extremely low. This clearly differentiates these shallow, low level treatments for indoor use from those used for heavy duty outdoor protection such as chromated copper arsenate (CCA) that may have very different disposal pathways.
It is technically feasible to compost H2F treated timber. The extremely small amounts of chemicals in the H2F treatments tend to bind to soil and organic particles in the ground where they degrade over a period of days to months, depending on the environmental conditions.
The other likely option is landfill. Nearly all modern municipal solid waste facilities are lined and the waste is tightly compacted and covered. This creates an essentially anaerobic (oxygen free) environment in which little to no degradation of timber occurs.
Examinations of timber excavated from older landfills shows little evidence of any degradation. The presence of small amounts of insecticide would have little or no effect on these processes.
To summarise, the disposal or repurposing of H2F treated timber is similar to that of most types of timber, the small amounts of chemicals in the H2F treated timber have a negligible effect on the process.
The benefits of H2F treated timber in replacing toxic chemical soil drenches to provide long-lasting protection and increasing the durability and service life of our homes significantly outweigh any other potential issues.
Professor Jeffrey J Morrell, director, National Centre for Timber Durability and Design Life
I am the author of the Spinifex article which Professor Morrell is referencing in this article. Unsurprisingly, I have a few thoughts in response! 🙂 But let me first say that I am in no way anti-timber. Quite the contrary in fact, and the track record of my writing, training materials, and built work proves I am a timber enthusiast! Wood is good! Ask my consulting engineers how often I query their steel structure designs by asking “Can’t we do that in timber?”
Unfortunately I share this passion with my little insect friends, and so we have to address the means of controlling their appetite for the stuff I like to build with.
I am pleased that in Australia we have developed a very sophisticated set of materials and design details for doing just that, which do not rely on toxins of any kind. This undergirds my position that H2F or T2 treated timber framing is unnecessary, gives consumers a false sense of security, and is building a landfill time bomb we will live to regret. Please refer to my piece in this column from a couple of weeks ago. I didn’t mention in that piece that carpenters are most often less than enthusiastic about handling it all day.
I also think it may be helpful to offer a few rejoinders to Prof. Morrell’s arguments, as follows…
“low toxicity to humans” ? no toxicity. Have tests been carried on carpenters exposed to it for a decade or more?
“Many currently occupied timber framed homes in Australia were built in the 1800’s.” – not built from H2F timber, but mostly from Class 1 durability Australian hardwoods. This statement does nothing to support its use.
“…few economical pathways for disposal of any framing timber other than landfill or composting. This situation can be expected to change as the market embraces and applies the concept of a circular economy in which there is a much greater focus on the retrieval and reuse of materials.” Bring on the circular economy! But at $55/hr for unskilled labourers (mainland capital city prices 2021), it is not happening any time soon. But untreated timber can also be burned – as either bio-fuel at commercial scale or in wood heating at domestic scale – H2F treated timber cannot be burned, and according to the waste disposal receivers I have spoken to, is not accepted for composting.
“H2F framing was introduced relatively recently, so at the moment there is very little entering the waste stream.” This is contrary to advice given to me by a major Sydney waste receiver, and comments from a waste consultant in response to the original article in Spinifex last week. Regardless, we all recognise there is a problem, we are just arguing about the scale of it.
“It is technically feasible to compost H2F treated timber. The extremely small amounts of chemicals in the H2F treatments tend to bind to soil and organic particles in the ground where they degrade over a period of days to months, depending on the environmental conditions.” What is the process of ‘binding’ and ‘degradation’? What are the chemicals left over and how long do they remain? Have these been tracked in soil and groundwater movement?
“Examinations of timber excavated from older landfills shows little evidence of any degradation.” So landfill is forever. Not really a sustainable solution then.
To summarise, “The benefits of H2F treated timber in replacing toxic chemical soil drenches to provide long-lasting protection and increasing the durability and service life of our homes significantly outweigh any other potential issues.” I disagree. The benefits of adhering strictly to AS3660 make the need for H2F/T2 treatment superfluous. The highly toxic chemicals used in the past do not justify the use of an unnecessary set of less toxic chemicals into the future – physical barriers and regular inspections are the truly sustainable option.