An international comparison: wood construction meets the objectives of the climate report

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The new UN Climate Report warns of wide-ranging and irrevocable consequences if carbon emissions are not taken under control. Because the volume of greenhouse gas emissions in the atmosphere is now at a record high, mitigating such emissions requires fast and concrete decisions. According to the report, the world has only a little time to keep global warming in check at reasonable costs. The aim is to reduce emissions by 40-70% between 2010 and 2050, and to end the consumption of fossil fuels completely by 2100.

In the opinion of Matti Kuittinen, a researcher at Aalto University, emissions-free, low-carbon wood construction offers a significant solution to achieving the targets set by the UN Climate Report in the built environment. – In order to achieve the targets set in the report, we must transfer to low-emissions construction and energy production in housing and transport.

Construction and the use of buildings cause about 40% of all CO2 emissions. According to an international comparison, the climate emissions of construction can even be halved through wood construction. In the EU, we are moving towards almost zero energy construction, so we must focus attention on construction and the manufacture of building products.

– Environmental specifications for building products based on European standards should be made compulsory, says Kuittinen. The calculation of the environmental impact of a building could be part of the planning permission process in the same way as the calculation of energy efficiency.

In Austria, for example, funding for public construction is tied to energy efficiency. – In public construction, we could also present a model for low-emission and energy-efficient construction. Finland could tie ARA funding to energy efficiency based on the Austrian model, and introduce emissions-based tax benefits well-known in the vehicle market, suggests Kuittinen.

The carbon footprint of a wooden frame half that of other materials

A comparison of the climatic effects of buildings in different countries shows that the carbon footprint of wooden buildings is less than half that of concrete buildings. The study compared the carbon footprint and energy needs in the manufacture of building materials used at 19 locations in Europe and North America.

According to report author and researcher Matti Kuittinen, in the light of the comparison, it can be said that the climatic effects of a timber frame are less, irrespective of the method of calculation.

– The result shows that European standards are becoming necessary. Although the comparison was carried out in a scientifically valid way, comparison and reading of the results is difficult without jointly agreed standards, which should start to be systematically observed as soon as possible and introduced into national building legislation.

According to the report, the carbon footprint of timber-framed buildings was on average 55% that of other frame materials.

– In themselves, environmental comparisons in construction are easy to do, as long as the comparative data about energy, natural resources and CO2 emissions are correct, says Kuittinen. Calculation and comparison should not be made too complex.

According to the new European standard EN 16485, at the start of their life cycle wood products may have a negative carbon footprint. The carbon storage of wood products may be given as additional data when assessing environmental impact.

Article service/Markku Laukkanen
Additional information: Matti Kuittinen, researcher, architect, 050 594 7990, matti.kuittinen@aalto.fi


Comparing the climatic effects of buildings

The comparison of the climatic effects of buildings was carried out on different types of buildings at 19 locations in Europe and North America.The study compared the carbon footprint and use of energy caused by the manufacture of building materials for building frames.

The carbon footprint of the manufacture of building materials for the Bridport apartment block completed in Central London in 2013 was compared with regard to CLT (cross-laminated timber) and concrete frames. Because of the timber frame used at this site, emissions were about one-fifth of those caused by a concrete-framed building. Emissions eliminated in this way are equal to the energy consumption of the building over 12 years.

The carbon storage and carbon footprint of the construction of the Murray Grove apartment block completed in London in 2009 were compared with regard to timber and concrete frames. Whilst the timber CLT frame stored almost 200 tonnes of carbon, the manufacture of a concrete frame of similar size caused 124 tonnes of fossil carbon emissions.

The carbon footprint over the entire life cycle of the passive energy-level PuuEra apartment block completed at Vierumäki in 2012 was compared with regard to timber and concrete frames. During the life cycle, the timber-framed structure produced 6% less greenhouse gases since the calculation did not take into account the significance of the timber frame as a carbon sink.

The carbon footprint of the manufacture of the frame for an apartment block in Växjö, Sweden, was compared with regard to timber and concrete structures. The timber-framed structure produced almost 60% of the greenhouse gases compared to the manufacture of a concrete frame for the building.

The carbon footprint and need for primary energy of the manufacture of the frame of the Metla Research Centre building completed in 2005 were compared. The timber-framed building produced 40% of the greenhouse gas emissions from a similar concrete-framed building, and used two-thirds of the energy consumption of a concrete-framed building. The same results were achieved in a comparison of the carbon footprint and energy need of the Centro Sociale and Nidi Nel Verde buildings in Italy. Also in a Polish energy-efficient detached house, the greenhouse gas emissions from the timber-framed building were about 40% of those of a masonry structure.

In Malmö, Sweden, emissions and energy needs caused during the manufacture, construction and demolition stages of the frame of a wooden apartment block were compared to those of a concrete frame. The patented wooden apartment block frame solution produced less than 10% of the greenhouse gases compared to a concrete-framed apartment block, and used less than 40% of the energy compared to a concrete building.

In Canada, the Athena Institute built type houses of wood, steel and concrete. Precise quantity surveying yielded a result according to which, with a timber frame, the same building produced two-thirds of the greenhouse gas volume of a concrete building and, with a steel frame, 80%.In terms of energy consumption, the timber-framed building used less than 40% of that of the concrete building and the steel-framed building about 70%.

In the USA, a comparison between type house frames was done using timber and steel. Depending on the type of house, the share of greenhouse gas emissions and energy consumption in the timber-framed house was about two-thirds that of the steel-framed house.

In Germany, the objects of comparison were the frames of houses built of wood and brick, and the carbon footprint and need for primary energy throughout the life cycle of the materials were compared. Greenhouse gas emissions from the timber-framed house were about 70% that of the brick house, and energy consumption during the life cycle was about 80% that of the brick house.

 

Source: woodproducts.fi

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