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Embrace wooden buildings for the sake of your health and the planet's

The burgeoning use of wood as a building material is a path to more sustainable construction, and it may have psychological benefits too, finds Graham Lawton

By Graham Lawton

6 June 2024

 

 

 

The Marcadet Belvédère project in Paris, a low-carbon development where the existing base has been restructured and the new elevation built in wood

Stora Enso partner: WO2/©L’autre image

 

A few years ago, I wrote an article about new uses of wood, including as a sustainable construction material. It was a surprise hit. Since then, we have covered wood technology as often as possible.

So when I was invited to Paris to visit two state-of-the-art wooden building projects, I jumped at the opportunity. One is a refurb, the other brand new, but both are built almost completely from wood and have enviable environmental credentials, as well as being aesthetically stunning. I have sung the praises of wooden buildings for years, but had never been inside one. Now I have, I am smitten.

My first port of call was a city centre development called Marcadet Belvédère, a former parcel terminus for the French railway network overlooked by the Basilica of the Sacred Heart. A long-abandoned eyesore, the developer WO2 is adding five extra storeys to the concrete shell to create office space. The new storeys are mostly made of cross-laminated timber (CLT), an engineered wood product that rivals concrete and steel as a structural material, but with a much lower carbon footprint.

 

 

 

According to WO2’s director of engineering, Laurent Petit, the wood the firm uses – sourced from Stora Enso in Austria – brings significant environmental benefits. Over 50 years, Marcadet’s total emissions will be half of what a traditional concrete and steel refurb would have belched out. That is largely due to the materials, but also reduced running costs.

“When we started to build in wood, the purpose was to reduce the carbon footprint, but then we discovered a lot of other benefits,” Petit told me. CLT is 80 per cent lighter than the combined mass of concrete and steel, so there is no need to reinforce foundations at financial and environmental cost. It is quicker to build with, requires fewer trucks and less heavy equipment to be brought on site, and has useful thermal properties.

A standard building has high “thermal inertia”, meaning it takes a lot of time and energy to warm up and cool down. But in a CLT building, the moment you start the heating, you start to feel the warmth in the atmosphere, says Petit. Cooling is less straightforward, but at Marcadet, this is aided by the plants and trees in the building’s rooftop garden. When it is hot, these evapotranspirate water from the soil and hence draw out heat from the rooms below.

There are wider thermal benefits too. During a heatwave, concrete soaks up heat and radiates it out at night, keeping the city sweltering. Wooden buildings don’t do this. Deadly heatwaves are a growing problem in Europe and are especially dangerous when there is no respite at night.

Wooden buildings can burn, of course, but Marcadet shouldn’t. “What burns in a building is the furniture, not the structure,” says Petit. “Yes, wood burns, but ignition is slow and almost never happens.” Marcadet is further protected by a sprinkler system pioneered in art galleries that sprays minuscule droplets of water. These don’t quench the flames directly, but cool the fire down. The droplets instantly evaporate and the latent heat of this process helps put out the fire.

Next, I visited an other WO2 project. Arboretum, on the western fringes of Paris, is a stone’s throw from the skyscraper jungle of the La Défense business district, but a million miles away in spirit. “It’s the largest wooden office project in Europe,” says Laurence Desmazières at investment fund ICAWOOD, one of the project’s backers. Arboretum is a campus comprising five new low-rise offices set in parkland. The buildings are made largely of CLT, which, as at Marcadet, means the project has half the lifetime carbon emissions of a standard new build.

Inside the buildings, the wood is deliberately and beautifully exposed on walls, ceilings and columns. “You can feel the wood, touch the wood, see the wood, smell the wood,” says Desmazières. “Wood also has very good acoustics. The idea is to offer nature to people inside the buildings.”

It isn’t just aesthetically pleasing. Contact with nature, even via the built environment, has proven health benefits. “Being in a wood environment helps from a physiological and psychological standpoint,” says Desmazières. “You’re less stressed and you sleep better.”

I would certainly swap my office space for a desk surrounded by gorgeous wood. In France, that will increasingly be on offer. Recent laws demand that developers calculate the lifetime carbon footprint of any new building. Those that exceed a certain threshold won’t be given planning permission. That is sending firms scurrying to source greener materials such as CLT, says Desmazières. “Wood has great days ahead.”