New Approach to Natural Material – Wood (CLT)
The U. K’s dedication towards a reduction in carbon and other greenhouse gas emissions is now a matter of legal obligation. Under the Climate Change Act 2008, emissions are aimed to reduce by 26% by 2020 (by comparison with a 1990 baseline) and by no less than 80% to 2050. (SUSTAINABLE DESIGN AND CONSTRUCTION SP GUIDE April 2014) As per the government’s new policy (www.london.gov.uk) regarding decreasing carbon dioxide emissions, a development proposal should make the maximum contribution.
The Mayor of London keen to increase the use of renewable sources, and encourage designers to project the capacity of renewable energy resources through versatile designing and by making vigilant choices for future generations.
The use of renewable energy exhibits a substantial opportunity to cut carbon dioxide emissions, and its development will also contribute to the security of the energy supply in London.
According to the Mayor’s policy, (5.7 Renewable energy), Mayor seeks to increase the proportion of energy generated from renewable sources in the construction industry.
A development proposal should make the highest contribution to reducing carbon dioxide emissions diminution in energy. Considering, construction is one of the main factors amongst many and according to U.K government’s report (Low Carbon Construction Innovation and Growth Team Final Report) buildings are responsible for about 50% of the country’s CO2 emissions, and in one sense this is true; as it emits 55% CO2 of the total emission.
The proportion of total UK CO2 emission that construction can impact. (Low carbon construction innovation and growth).
One of the prevalent benefits of considering wood as a building material is, it is a natural resource, making it easily obtainable and economically reasonable. Wood is exceptionally solid concerning its weight. And it offers good insulation from the cold. Because of its highly machinable quality, it allows to experiment with forms; therefore, it can be into all kinds of shapes and sizes to fit practically and any construction requirement.
It is also an ideal example for the environmentally sustainable product as it is biodegradable and renewable, and it transmits a low carbon footprint in comparison with any construction material. Unlike any other construction material while producing wood no high-energy fossil fuels are required.
Timber is used most frequently in the construction industry. Wood has several benefits that’s why it stands out as an excellent candidate for use in a wide range of construction projects. Unlike steel which expands or even collapse in high heat, wood dries out and become stronger in high temperature. Its thermal properties, which is the biggest advantage to resist high temperature. But over these years despite having such versatile nature of wood, its use in the industry was limited. (http://www.understandconstruction.com)
Trees absorb carbon dioxide while they grow. When the tree is harvested the carbon remains stored in the timber until the end of its physical life, roughly one ton is stored in the per meter cube. Hence, the carbon is safely locked up in timber products; such as walls, windows, doors, or floors. Therefore, more trees are planted, to absorb and store carbon as they grow. The amount of carbon produced during harvesting, processing, manufacturing, and transportation is lower than the amount of carbon absorbed by trees. This helps to reduce the emissions process.
If we built 250,000 new houses (which is the predicted number for future need) in timber it would store around 4 million tons of carbon dioxide every year. Embodied carbon can be reduced to 30%to 50% of the carbon emissions from a new building throughout its lifetime. This number can be minimized by utilizing more ecological and renewable natural materials such as timber. (woodforgood.com)
Structural engineers have proposed engineered timber product called CLT- Cross Laminated Timber. Which has good structural properties and low environmental impact. Specified timber is sustainably sourced material therefore, there are environmental advantages in the use of CLT, such as the embodied carbon of timber products is relatively less to many other construction materials. As it is a natural renewable product performance can vary slightly, but commercial cross-laminated timber generally attains:
Thermal conductivity: 0.13 W/mK
Density: 480–500 kg/m3 (spruce)
Compressive strength: 2.7 N/mm2 (perpendicular to the grain of boards)
Bending strength: 24 N/mm2 (parallel to the grain of boards)
Elastic modulus: 370 N/mm2 (perpendicular to the grain of boards) Reference for standards, (www.bre.co.uk)
As it is plant-based materials, carbon gets stored in trees while they grow and continues to be stored through its use as a building material. At the end-of-life tree, carbon is released either through natural decomposition, returning other nutrients to the soil, or through the generation of heat/ energy by burning it as a fuel, either way, providing a comparatively highly efficient end-of-life treatment. In order, to reduce co2 emission materials used in construction plays a vital role, concrete is an extensively used man-made material in existence that should be replaced by CLT (Cross Laminated Timber).