Impact of climate change on timber engineering structures - Research Paper Example

?Climate change presents a unique set of challenges and opportunities in the face of global warming and climate change. On the one hand, existing timber constructed structures are under increasing stress due to climate change while on the other hand a number of opportunities are offered by timber structures to slow down global warming. The differing opportunities and threats posed by timber structures and climate change are outline below. 1. Timber Structures and Bushfires Climate change has been related to bushfires directly and increasing temperatures have been taken as a sign that bushfires are only bound to increase in the future. An estimate puts the change in temperature due to global warming in Australia between 0.4 and 2oC by the year 2030 above the 1990 levels while the change by 2070 is projected between 1 and 6oC. (Preston & Preston, 2006) It could easily be expected that the exposure of timber to bushfires would result in the timber structures being damaged beyond repair by fires. However this is not entirely true as timber structures do not face any real threats as long as the heat from the bushfires is radiant in nature. Appropriately AS 3959-2009 specifies three classes of timber that can be used in areas at risk of bushfires. These ratings are based on the BAL (Bushfire Attack Level) ratings and include timber with a seasoned density of 650 kg/m3, 750 kg/m3 and timber that is resistant to bushfire. Timber is made resistant to bushfire through the use of the materials inherent properties, by dousing and coating with fire retardant chemicals or through the application of fire retardant substrates. (Standards Australia, 2009) However AS 3959-2009 does not place any constraints for using special timber classes in places where no direct exposure to heat is speculated. Such regions of timber usage include the floors, wall frames, roof framing walls, ceiling lining etc. The timbers specified for use in the standard mentioned above are found abundantly in Australia. Seven kinds of timbers with high densities are specified as being fire resistant and their testing has proved the levels of endurance that could be expected with their use. Based on these pieces of evidence it can be inferred that timber can be used in increasing numbers without the risk of significant impacts from climate change on timber engineered structures. 2. Spread of Termites and Other Pests Another major impact of climate change has been its help to spread various species of insects beyond their normal modus operandi. The increase in temperatures is driving more and more species to occupy newer areas. In the Australian context there has been a net migration of a number of different plants, animal an insect species towards the south as temperatures are on the rise. The increasing temperatures provide these species with better breeding grounds that are favourable so a net migration occurs. The case of malaria moving farther down south is just one such manifestation (McMichael, 2003) where the operating areas for mosquitoes have increased as global temperatures are on the rise. A similar problem is exhibited through the spread of termites to newer locations as temperatures become more and more favourable for their breeding and growth. Regions like Victoria are more at danger than others because 30 of the 78 municipalities in Victoria do not require any anti-termite protection for buildings. This indicates that most of the buildings, houses and other structures in these municipalities will be prone to termite infestations in the near future. At present there is little to no action on the part of the government to mitigate such threats. The various builders, developers and purchasers should be alerted by the local government as to expected chances of termite and other pest based infestations. Moreover there is dire need for coordination between government regulatory agencies and etymologists in order to identify the migration patterns of termites and other such pests that could cause large damages in the future. 3. Increased Moisture Levels and Timber Structures The overall climate change scenario would also involve changes in the levels of relative humidity in the air. The amount of relative humidity experienced in air is expected to grow as a result of climate change though there are no exact figures to quantify the total change. As a consequence of increased relative humidity, the water content in air will be all the more responsible for catalysing the decay of wood and wood based materials. Given the nature and composition of timber based structures, it is highly apparent that they would be directly affected. Moisture tends to permeate the wood structure and this in turn leads to a change in the dimensions of the timber structure members. The realignment required can be gruesome if proper adjustments for expansion and contraction are not made available in the structure’s design process. Moreover the permeation of moisture into the joints of the structure could initiate fungal growth in these locations that would have long term detrimental effects. Not only this, the constant exposure of timber framed structures to the sun and high levels of moisture would encourage and facilitate the growth of fungal colonies on the exposed portions of the timber framed structure. Though these threats are highly real and seem intimidating but the use of appropriate technological advances and fulfilling design criteria can ensure that a timber framed structure can easily stand up to problems caused by excessive moisture in the air. Structures composed of timber have been built in areas with a high level of moisture such as the Scottish highlands and near seas and some of them have survived to this day even though they were subject to high moisture levels. The primary technique required to protect timber from moisture based rot and decay is to protect the surface of the timber in such a manner that it becomes impenetrable. Moreover the coating applied to the surface of the timber must be able to resist environmental factors for a large amount of time so that moisture permeation is avoided. The joints and other such crevices found in timber based structures can be easily sealed up using commercial sealants resistant to moisture content. These flexible sealants would allow joints that allow the building structure to both expand and contract while not being open to moisture permeation at all. (NHBC Foundation, 2007) 4. Environmental Costs of Creating Building Materials 4.1. Environmental Impact during Manufacturing The processes used to manufacture any kinds of goods involve the use of methods and processes which produce green house gases which are ultimately responsible for global warming and climate change. Construction materials such as cement, concrete, steel and others are all produced with similar methods and processes such as crushing, smelting, mixing, baking etc. which involve the use of fossil fuels and wastage of water. This indicates that there is a fixed environmental cost with the production of such construction materials. (Froeschle, 1999) On the other hand when timber is considered as a construction material, it can be realised that producing timber is the most environmentally friendly method of all. Timber essentially uses up nutrients produced from the ground and the eventual cutting and shaping processes require little use of fuels and other such resources. The tables presented below compare conventional construction raw materials with timber for their total environmental impact during manufacture. A look at the data presented in the tables above clearly indicates that the production of timber actually reduces carbon in the environment unlike all the other construction materials that positively contribute to increasing carbon in the environment. Only concrete can come a little close to timber when it comes down to environmental impact during manufacturing but even then the carbon released and the fossil fuel energy levels required to create concrete are far too large to declare it as environmentally friendly. Based on this data it is apparent that timber holds a very secure future when it comes to renewable construction materials. 4.2. Environmental Impact in terms of Renewable and Non Renewable Construction Materials Another aspect of this issue emerges when it is considered that growing timber is a renewable pursuit – timber can be harvested and then grown again without much trouble. However the case of other construction materials is markedly different. The non renewable group of construction materials such as aluminium (derived from bauxite), iron (derived from iron ore such as haematite, magnetite etc.), concrete (derived from cement, sand and aggregate), bricks (derived from clay) and glass (derived from sand) are all finite and hence will be used up at one point in time or the other. Timber and other similar wood based construction materials are renewable and can be expected to outlast their compatriots by quite some margin of life. When it is considered that nearly every year around three billion tonnes of raw materials are processed and out of these, one half is diverted for use in the construction industry alone, (Roodman & Lenssen, 1995) the true extent of the issue becomes apparent. The construction industry consumes too many raw materials as building products and allied materials and in doing so it places a lot of burden on the environment. 4.3. Resurgence of Timber as a Prime Construction Material Even though it is well recognised that the production of non renewable raw materials for construction have large unwanted impacts but their use could not be slowed down especially in the wake of the Industrial Revolution. The massive increase in population and the dearth of timber to support the new modes of construction (such as multi-storey buildings) demanded that newer construction materials be explored. This trend has continued unabated for decades since the post Industrial Revolution period but given the situation of global warming and climate change, there has been renewed interest in using more renewable materials for construction. Timber has resurfaced as a prime option for use in the renewable sector of construction materials. Moreover new research and techniques are being developed and implemented in order to harvest lumber from dense trees using as small a life cycle for growth as possible. (Spiegel & Meadows, 1999) (Hipps et al., 2006) This will ensure an adequate supply of lumber and timber as older trees are used up and new are grown. The use of more and more timber in the construction industry is expected to reduce the burden on more conventional raw materials and hence the environment. 5. Environmental Impact Assessment through LCA (Lifecycle Assessment) Material LCA (lifecycle assessment) is carried out in order to evaluate the total impact of construction materials on the environment through their total lifecycle such as their production, use and termination of use. A comparison carried out between seven different case studies conducted across the globe in Sweden, Canada and the United States revealed conclusively that the use of timber required the lowest energy and displayed the lowest environmental impact. (Erikson, 2004) The results from this study are shown below. Based on the results of this study it can be conclusively said that timber produces the lowest impact on the environment throughout its lifecycle. This is all the more evidence to prove that timber possesses the necessary traits to emerge as the preferred material for renewable construction. 6. Use of Timber after Useful Lifecycle Timber also offers the option of being reused after its primary application in a building structure. For example timber structural members can be sawed down and used as recycled components in newer structures such as towers etc. The total impact on timber structural members during their service life is well understood so it can easily be used to assess the condition of a timber member before use. The recycling of timber structural members ensures that the total use of timber increases along with a net decrease in its environmental signature. Moreover the scrapped timber can easily be shredded and converted into pressed boards and furniture. The use of timber in this fashion ensures that the total environmental impact of timber remains low and that carbon emissions are contained. 7. Bibliography Erikson, F., 2004. Demystifying Data Construction and Analysis. Anthropology and Education Quarterly, 35(4), pp.486-93. Froeschle, L.M., 1999. Environmental Assessment and Specification of Green Building Materials. The Construction Specifier, p.53. Hipps, N.A., Atkinson, C.J. & Griffiths, H., 2006. Pruning trees to reduce water use - summaries of research, conclusions and recommendations. Investigation Summary. Watford: BRE Press Gartson. McMichael, A.J., 2003. Human Health and Climate Change in Oceania: A Risk Assessment. Investigation. Commonwealth Department of Health and Ageing. NHBC Foundation, 2007. Climate Change and Innovation in House Building: Designing out Risk. [Online] NHBC Foundation Available at: http://www.nhbcfoundation.org/LinkClick.aspx?fileticket=viZ9mWU9cqQ%3D&tabid=339&mid=774&language=en-GB [Accessed 29 October 2011]. Preston, B.L. & Preston, R.N., 2006. Climate Change Impacts on Australia and the Benefits of Early Action to Reduce Global Greenhouse Gas Emissions. [Online] CSIRO Available at: http://www.csiro.au/files/files/p6fy.pdf [Accessed 30 October 2011]. Roodman, D.M. & Lenssen, N., 1995. A Building Revolution: How Ecology and Health Concerns are Transforming Construction. Worldwatch Paper , 124, p.5. Spiegel, R. & Meadows, D., 1999. Green Building Materials: A Guide to Product Selection and Specification. New York: John Wiley & Sons, Inc. Standards Australia, 2009. AS 3959-2009 Construction of buildings in bushfire prone areas. [Online] Available at: http://infostore.saiglobal.com/store/Details.aspx?productid=1101539 [Accessed 30 October 2011]. Read More