A German study on the greenhouse emissions of residential building construction concludes that timber is the most sustainable material for housing projects.
Author: Pollmeier
Photos: Pollmeier

Residential construction and CO2 emissions

The „THG-Holzbau” study carried out at the Ruhr University Bochum is unambiguous in its conclusion: in order to protect our climate and reduce greenhouse gas emissions, more residential buildings must be built in timber – starting today.

Although the population of Germany is declining, the demand for housing is still on the increase. According to the „empirica” forecast, this trend will continue at least until 2030. There are many reasons for this development: growing prosperity, a trend towards smaller households and an ageing population are only some of them.

In order to meet the demand, there is currently a building boom – which means of course that there is also a greater demand for construction materials. This aspect was examined in the „THG-Holzbau” research project under the auspices of professor Annette Hafner. It aimed at identifying the impact of specific construction materials on climate change.

Timber is the key to sustainability

The researchers were able to show that the use of timber and timber-based materials helps reduce greenhouse gas emissions. Wood stores large amounts of CO2, and timber constructions keep this greenhouse gas out of the atmosphere. In addition, mineral construction materials such as concrete or steel require a lot of energy in their production, which results in large volumes of greenhouse gases being released into the atmosphere.

Where mineral materials are substituted with timber and wood-based materials, there is thus a double positive effect on our climate – at least in theory. On the one hand, CO2 captured in the timber remains there. On the other, the „grey energy” load is reduced.

Timber comes top

In order to quantify the substitution potential of timber constructions, the „THG-Holzbau” project team compared the carbon footprints of residential buildings made in timber with those built with mineral materials. The results speak for themselves: according to Annette Hafner and her team, greenhouse gas emissions can be reduced by 35-56% per m² GFA in detached/semi-detached houses and 9-48% per m² GFA in apartment blocks.

In other words: per m² gross floor area, between 77 and 207 kg/m² CO2 equivalents can be saved with a timber-built detached/semi-detached house. For an apartment block, the figure is 18 to 178 kg/m² GFA. The substitution rate depends of course on a number of factors such as the actual construction materials, the design of the building, its size, insulation rating, etc.

A detached family home (GFA = 320 m²) built in timber saves more than 66 tons of CO2 equivalents, which corresponds to the annual CO2 footprint of seven people in Germany.

Great savings potential in interior finish

Apart from the actual supporting structure, Annette Hafner and her team show that there are huge potentials for saving when it comes to the interior finish of a home. By opting for timber floors, windows, doors and façade cladding, the CO2 footprint of a house can be significantly reduced.

The savings that can be made with fittings and fixtures are particularly relevant, as these elements generally need to be replaced several times over the lifespan of a house. By opting for timber in refurbishment projects, it is thus even possible to reduce the impact of existing concrete and steel-built homes on climate change.

Challenges and opportunities

Considering the number of new houses that will be built over the next few years, even a moderate increase in the use of timber in their construction will significantly reduce the CO2 footprint of the new housing stock.

On paper, this looks all very well. The timber industry is however not yet ready to grasp the opportunity. The reasons for this and possible ways forward have also been identified and analysed in the study, which includes task lists for all parties involved in timber construction and its promotion: while associations should focus on a common strategy and further training in the field of timber construction, R&D institutions should publish reliable data, make more information available, harmonise the relevant standards and promote the transfer of knowledge. At the political level, building regulations need to be updated, while manufacturers and processors must expand their production capacities. There is still a lot to do until more sustainable construction methods will be the norm.

Residential building construction is just the start

The „THG-Holzbau” study shows what can be achieved with regard to climate protection in the residential building sector. Other categories such as commercial buildings and refurbishment projects are to be examined in the course of a separate project.

Annette Hafner and her team of researchers are however eager to see their recommendations implemented. To significantly reduce greenhouse gas emissions from construction, the number of houses built in timber and wood-based materials must increase immediately and on a large scale. What is needed urgently is a move away from conventional construction materials to more sustainable resources, as the protection of our climate is one of the most pressing issues of our times.

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