Wood – a green choice

on 09 September, 2013

Most of us want to make choices that reduce our impact on the environment, or at least avoid making ones that are overtly detrimental. When it comes to choosing building materials, it can seem like every choice is a bad one.

Man-made materials are very hardwearing and incredibly strong, but they come with a host of serious and complex environmental problems:

  • Concrete creates huge quarry scars across our landscapes and uses enormous amounts of energy to manufacture and transport
  • Metals also have to be quarried and then manufactured in a process that pollutes and belches greenhouse gases. In particular, aluminium production results in the release of perfluorocarbons, which permanently pollute the atmosphere and are some of the worst greenhouse gases
  • The cement industry is one of the largest emitters of greenhouse gases
  • Plastics are made from precious hydrocarbons in a process that creates pollution. At least aluminium can be recycled – most plastics cannot.

There is only really one natural material suitable for building – wood. Hardwoods are strong and long-lasting but it is almost impossible to be sure you know where the wood has come from. How can you be sure it has not been illegally logged? Given the time taken to grow replacements and the areas of the world these woods are grown in, can it ever be considered to be a truly sustainable material?

Softwoods can be sustainably grown. The trouble is that softwoods are – well, soft. They don’t have the strength or lifespan of their hardwood equivalents. Most softwoods expand and contract a great deal, weakening joints and creating air gaps around windows and doors.

The good news is that there are commercially available products which combine the sustainability of softwood forestry with the structural characteristics of hardwood. These are treated or modified woods.

Traditional wood treatment processes impregnate the wood under pressure with a range of compounds like copper arsenic, zinc naphthenate and ammoniacal copper quaternary. These chemicals stay in the wood and prevent insects attacking and moulds and fungus growing, but the process used creates pollution. In addition, there are concerns that these chemical residues may be toxic – particularly when burned or used near vegetables and herbs.

However, there is an alternative wood treatment process that has been developed called acetylation. This process changes the chemical structure of the wood, which gives it two distinct benefits. Firstly, the wood does not absorb water freely so it is much less prone to swelling and contracting, making it more dimensionally stable. Secondly, its structure becomes less reactive, making it less prone to decay. The by-products of the process are fertiliser and small amounts of biodegradable vinegar.

Our short video explains in simple terms why this process is considered to be sustainable and environmentally friendly.

This article has been written by Accoya Modified Wood. 

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