Buildings generate nearly 40% of the annual global greenhouse gas emissions. What buildings are made of has a huge impact on the climate. How much CO2 emissions could be reduced by using timber in the construction sector?

Ali Amiri from the Aalto University in Finland and his colleagues Juudit Ottelin, Jaana Sorvari and Seppo Junnila looked at the carbon storage of 50 wooden building.  The research team compared the buildings’ structures with different sizes, uses, and locations and developed three levels of carbon storage, depending on the amount of wood used for the structures and the furnishing. Ali gave us an interview about his great research.

What was your personal motivation for your research on wooden buildings and their contribution to the climate change?

Buildings are considered as one of the most cost-effective solutions for climate change mitigation although they produce a third of greenhouse gas emissions. Here we need a material like wood which produces less emissions compared to the main building construction materials, i.e. steel and concrete. On the other hand, it should have acceptable characteristics e.g. structural, in order to be used in building construction.

What is a wooden building? Is there a Europe-wide definition?

Any building that has some wooden components especially structural ones might be considered as wooden buildings, but I have not seen any definition based on their carbon storage potential. For the first time we categorized wooden buildings into three levels: level 100 (low), which store 100 CO2 kg m−2; level 200 (mid), which store 200 units; and level 300 (high), storing 300 units.

What are the advantages of working with wood instead of concrete and cement in the construction sector?

Regarding climate change mitigation, wooden buildings are beneficial in two directions. First, they produce less emissions during their production phase compared to steel or concrete ones according to most studies done in literature. Second, wooden buildings have the potential to store carbon for long time during their life cycle.

Does the optimal climate-neutral building already exist?

Building mainly use energy and produce emissions during pre-use and operation phases. Even if they produce less emissions or store carbon for pre-use phase, the operation phase plays role so there is need to optimize energy use during both phases.

Is there a global or EU-wide certificate for buildings that capture carbon?

This is not completely incorporated in green building certificates. Some include life-cycle assessment (LCA) as a sustainability tool. It depends on the type of LCA and the boundaries defied for the project in order to find out if carbon capture is included or not. Our next paper is about this topic that is in the progress.

Are there any incentives for real estate developers in the EU for the construction of wooden buildings?

This depends on the requirements by the government and the awareness of end-users. In some municipalities, it is needed to include the emissions produced per m2 of the building which seeks the building construction permission.

In general, are wooden buildings much more expensive than buildings made of concrete, bricks, cement or steel?

Our paper focus was not about this but there are some papers that have concluded there is no cost difference for single or apartment building if constructed with wood instead of concrete or steel. Some others found out more cost for the design phase because of lack of wooden buildings designers.

How can it be ensured that the timber comes from sustainable forests?

This is mainly related to sustainable forest management. But I should mention that the volume of wood used for building construction is very limited compared to other uses. In addition, developed regions (Europe, Oceania and North America) have been successful of keeping their forest area stable from 1990 to 2010 while developing regions (Asia, Africa and South America) have lost 135 million hectares of their forest area according to FAOSTAT dataset.

Read the full study here.