As architects and specifiers make decisions today about the buildings and structures for the first years of the 21st century, Britain’s oldest building material is re-emerging as the truly modern answer to today’s building design challenges.
Sustainable construction has become a common term over the past few years. The idea of sustainable development incorporates not only environmental concerns, but should also take into consideration the social and economic aspects of society. In practice, it means that all buildings should be designed, built and maintained to meet the needs of society, to encourage social communities to flourish, but without damaging the environment for future generations.
Construction materials and the environment
Construction and the in-life use of buildings have a massive impact on the environment. The manufacture and transportation of building materials consumes 10% of the UK’s total energy consumption, whilst in-life energy consumption accounts over 50%. Buildings and building materials also contribute to many other environmental impacts through their lives, from the use of chemicals, land, water, and subsequent emissions. It is therefore extremely important that designers build to minimise environmental impact.
Environmental decisions about timber specification have tended to focus on the impact of its extraction on the forest resource. Though of great importance, habitat conservation is only one of the environmental issues that needs to be considered throughout the life of a material.
Of course, alternative materials, such as concrete, steel or plastic will also have an impact on biodiversity where the raw materials are extracted, and in the land take of processing operations. However, as woodlands also have aesthetic and recreational values, which quarries, for example, do not, a higher value is often placed on forest protection than for many other ecosystems.
However, there are many environmental considerations to take into account when assessing the 'green' credentials of a product, such as climate change, ozone depletion and ecotoxicity. For example, a product may have high energy requirements for processing that will contribute to global warming, or it may lead to environmental problems through its disposal.
There are therefore many areas where timber has an environmental advantage in comparison to other materials: it is renewable, and can reproduce to maintain an infinite supply; and it is energy efficient, having low embodied energy as well as good insulation properties. Trees play a major role in the world’s carbon cycle, and forests store a huge amount of carbon, and can therefore be used to alleviate global warming.
But how is it possible to make meaningful comparisons of environmental impact between a natural regenerating material, such as timber, and highly processed products such as steel, plastic or concrete?
The first stage is to establish exactly what impact a product will have, taking account of all stages of its lifecycle: from the extraction of raw materials; through processing and transportation; to in-life use, re-use or recycling, and finally to disposal. This holistic form of study is known as Life Cycle Assessment (LCA).
LCA differs from other methods of evaluating environmental impacts in its wide-ranging approach, and because it is based on quantifiable data. It is therefore seen as a much more objective way to identify environmental impacts. Once a product's inputs and waste emissions have been accurately measured, a clearer picture of its full impact will start to emerge.
Specifiers and consumers are demanding more credible information about the environmental impacts of products, and using LCA can show that business is taking their concerns seriously. LCA can provide the basis for environmental purchasing decisions and it will become increasingly important that industry is able to provide environmental data to ensure future markets. Not only that, but it is also a useful tool for the producer to identify its products environmental 'hotspots'.
1999 saw the publication of the Building Research Establishment’s Environmental Profiles Database. Forests Forever and the Timber Trade Federation have been actively involved in this project as a member of the steering group, and in gathering data from the timber industry for analysis by the BRE in line with the agreed methodology.
The methodology has been based on the ISO guidelines for LCA studies, and its aim is to enable a fair comparison of the environmental impacts of building materials to be made over their whole lifecycle. Each trade association has been asked to provide data for their material sector, and the end result should enable architects and specifiers to make better-informed decisions about which materials to use for each building element.
A UK National Database showing ‘environmental profiles’ for the various materials has been created which shows the environmental impacts associated with each material. This information can then be used to build up environmental profiles for individual buildings, and to minimise environmental impact by choosing materials that have the best profile over the anticipated lifespan of 60 years.
Environmental Profile for timber
The first stage reports from the BRE’s extensive research into the environmental profiles of building materials have reinforced timber's claim as the ‘green’ building material of choice. The results have shown clear environmental advantages for timber, particularly in the impact field of climate change where timber’s low embodied energy and carbon storage properties actually give it a positive impact. This applies even when taking account of the CO2 released through its transportation and processing.
The study looked at thirteen different environmental impacts ranging from climate change, pollution to air and water, waste disposal and transport pollution and congestion.
Other comparative studies have also shown that timber has advantages in comparison with alternative materials. At the Athena Institute in Canada, one of the first organisations to use LCA to analyse the impact of building materials, research has shown that wood is the best environmental option under a range of different impact categories. A case study using wood, steel and concrete design options showed that the wooden structure had the lowest impact for all factors considered: climate change, air and water pollution, solid waste production and total energy use. As examples, the steel design generated 120 times more water pollution than the wood option, and the concrete design produced 1.67 times more air pollution than the equivalent wood design.
Forests Forever and the Timber Trade Federation are continuing to gather data on the environmental impact of timber to improve the accuracy of the profile.
The main focus of current research falls into two areas:
Impacts from beyond the factory gate (the manufacturer, importer or merchant) - examining impacts of construction, in-life use, demolition and disposal;
Harvesting, processing and transportation in some of the major timber-producing countries supplying the UK market.
For many years, the timber industry has been on the defensive, tackling the criticisms that have been levelled at it over forest management. Now its time to remind the public of the many positive environmental attributes that timber has to offer.
By taking a more holistic approach, and by highlighting timber's strengths through solid, scientific information, we can ensure timber’s reputation as the world’s most environmentally friendly construction material.
