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Sustainable building with wood

Sonya Angelica Diehn Bonn, Germany
January 4, 2018

When you think "sustainability," building with wood isn't necessarily the first thing that comes to mind. But a deeper look at the growing trend begs the question: Could wood be a key sustainable resource of our future?

Architekt-Energiehaus Berlin Zernsdorf
Image: DW/Thomas Kakareko

Travel to a developing country, and once you get off the beaten path and out into any forested area, you are likely to see truckloads of felled trees being ferried away.

Wood comes from forests — so typically, timber is associated with deforestation. And deforestation is a key environmental problem: not only does it destroy ecosystems and habitat; it's also a major factor driving climate change.

So wood isn't an obvious choice for eco-friendly construction. But with man-made materials leaving a huge carbon footprint, wooden architecture is enjoying a resurgence.

It's even being touted as our only significant renewable construction material.

Secondary forests, sustainably managed

To assess sustainability, the entire life cycle of a product must be considered. And that starts with the source. If primal forests are clear cut to provide timber — be they in the Amazon, Indonesia or the Pacific Northwest of the United States — that does not represent a sustainable source.

But in many densely populated parts of the world, including in Central Europe, people have used forests for many generations, and changed them in the process.

"Our European forests have been used for centuries, and are highly humanized in many ways," says Marc Palahí, director of the European Forest Institute, an international research organization.

View over the forest in Germany's Rhineland-Palatinate region
Most European forests have been cut down, have grown back, and been cut down againImage: picture-alliance

In Germany, for example, most forest is secondary, meaning it's been cut down and has regrown.

Timber extraction meant German forests were already shrinking in the 18th century, and foresters responded by considering how to manage them sustainably.  

German forester Bernd Sommerhäuser explains the fundament of sustainable forestry: "What's used does not exceed what grows back — constant conservation is the goal."

Sommerhäuser says intervention in German forests isn't just sustainable — it's actually essential to preserve their biodiversity. "If we were to leave the forest over to itself here, it would normally develop into a stand of pure beech trees."

Building carbon-neutral(ish)

Once upon a time, wood was a primary building material across much of the world. But with industrialization, that changed in the West.

German architect Arnim Seidel explains that steel and concrete became the dominant building materials for to meet 20th-century demands: wide bridges, tall buildings, heavy loads.

"Wood came to be seen as backwards," Seidel told DW.

Construction workers pouring concrete into rebar while erecting a new building in Dallas, Texas
Concrete and steel rose to prominence to meet the needs of industrialized socieies - but their carbon footprint is hugeImage: picture-alliance/dpa/L.W. Smith

Now, its environmental advantages are being recognized.

Materials like steel and concrete require massive amounts of energy to produce, and are usually transported over long distances. This emits CO2 that contributes to climate change.

By some estimates, producing a ton of concrete, or about a cubic meter, generates 410 kilograms of CO2 equivalent — the same amount of energy could power an average house for more than 10 days.

Locally harvested wood from sustainably managed forests not only has a much smaller carbon footprint in its production.

Using wood in buildings also sequesters carbon dioxide. When plants perform photosynthesis, this removes CO2 from the atmosphere and stores it in the wood.

"When we build with wood, we can conserve this stored CO2 for a longer period of time, and not emit it into the atmosphere," Seidel told DW.

Building with wood, a growing trend

Wood has many benefits when it comes to construction: It's relatively lightweight and flexible, but also strong. It can be molded into various shapes, and is easy to transport to construction sites. Seidel says the possibilities of building with wood are virtually limitless.

Visualization of a wooden skyscraper planned for Hamburg's Hafencity
The sky's the limit in building with wood - literally. Hamburg's Hafencity is planning a wooden skyscraperImage: picture alliance/dpa/Störmer Murphy und Partner

Wooden skyscrapers are springing up in Canada, the United States and cities across Europe. Seidel describes these as "lighthouse projects" for sustainable building with wood.

But more mundane projects make up the bulk of wooden construction — even if they draw less attention. In Germany, about a quarter of residential homes and apartment buildings are now being built out of wood.

For public relations consultant Susanne Roth, sustainability — including carbon sequestration — was a major reason to invest in a multistory cohousing apartment on the outskirts of Bonn.

Holzbauprojekts Hummerichs Bitze - Susanne Roth
Roth also describes an emotional bond with wood, as she loves to be in the forestImage: DW/S. Diehn

Although there's not a lot of wood visible, the building — which consists of eight apartments — uses 190 cubic meters of wood, amounting to 190 tons of CO2 pulled out of the atmosphere. That's equivalent to taking about 40 cars off the road.

Building with wood involves highly developed, efficient technology, explains master carpenter Sebastian Adams, who's been hired to build the project.

"Wood waste, for example unusable sizes and shapes, is pressed into particle board, which helps brace the building," Adams told DW.

Wooden buildings are stable, durable and safe, Adams says. Wood is not nearly as flammable as you might imagine — and working with other materials helps encapsulate fire risks.

And there other advantages: "There's nothing so pleasant as walking barefoot over a nice, warm wooden floor. It also smells nice," Roth says happily.

Enough wood for a bioeconomy future?

So all is well and good with wood. Or is it?

Critics point out that wood is only as sustainable as its harvesting process. And that depends on sustainability certification schemes, which can have holes.

Trucks transport illegally logged timber from Myanmar to China
Countries with governance problems are often racked by illegal logging, such as here in MyanmarImage: picture-alliance/AP Photo/J. Holden

Then, there's only so much secondary forest that can be harvested and replanted. So what happens when demand exceeds supply?

"We need to ensure that the few old forests we have in Europe — because in Europe, we have very few primal forests — are preserved," Palahí says.

So, no clear-cutting of old-growth forests. One possibility would be to plant more trees, which would also help the climate.

Palahí says we need to "compromise between using the forest for wood and at the same time preserving biodiversity."

Forests don’t just harbor biodiversity. They also protect water sources and sustain soils. Beyond that, they could increasingly provide the building blocks of the future bioeconomy — an economic system based on renewable, bio-based resources.

"European forests are important sources of renewable biological resources, which we will need to replace the existing petroleum-based steel and concrete if we want to address the problem of climate change," Palahí says.