It also can put people back to work and save our forests.

TreeHugger has been covering the mass timber scene for a dozen years, starting with Waugh Thistleton’s timber tower in Hackney. Now Tim Smedley of the BBC talks to Andrew Waugh and writes a really thorough article that looks at the benefits of building with wood. He starts, as we do, with the carbon footprint, and the fact that trees are the best form of carbon capture and storage. Waugh says:

Dalston Lane/ Lloyd Alter/CC BY 2.0

Smedley and Waugh visit Dalston Lane, as TreeHugger did a few years ago. At the time, it was the largest CLT building in the world. Waugh explains how the building is much lighter than concrete (important when you are built on top of a train line) and how much carbon it stores.

© Waugh Thistleton

To really draw down CO2, all the trees that are cut have to be sustainably harvested and replaced with new planting. When I have complained to Waugh that as much as half of the mass of the tree is left behind in roots and slash, he responded: “Plant two trees!” For mass timber to really work the way it is promised, that is the kind of analysis that will have to be done – how much planting is necessary to not only replace the trees that were cut but also the CO2-releasing parts left behind.

There are other benefits to harvesting wood that go beyond the straight CO2 calculation. Smedley writes:

Andrew Waugh in front of CLT building/ Lloyd Alter/CC BY 2.0

Small diameter trees are just fine for making CLT. Waugh continues on this theme: “At the same time as solving climate change, making better buildings, we can help rural economies… These vast forests are basically rotting and burning down.” It’s as if, he says, “we kept on breeding cows but we stopped eating beef.”

There are going to be bumps on the way; in the UK they have banned combustible exterior walls on buildings over six stories in the wake of the Grenfell disaster, even though that building had plastic windows and plastic insulation and cladding and CLT doesn’t burn in the same way.

But no matter how you calculate it, the upfront carbon emissions of making mass timber are a fraction of those of making steel and concrete. Those industries are pushing back hard and even pushing out life cycle analyses demonstrating that over 50 years their buildings are not much worse. But we don’t have a lifecycle; we have to worry about what we are emitting now, and in the next ten years. If we are going to build at all, we have to do it in wood.