CA10 - Knock on Wood
Mass Timber is all the rage, wood you beleaf it?
THE TOPIC - MASS TIMBER
I really love wood products. There is something so unique and beautiful about each piece. It has depth, character, and personality, unlike most other materials. Where steel and concrete are flat and monolithic, wood is complex and dynamic. Enough of my love though, what’s so great from a carbon perspective?
Have you ever thought about how amazing the process of photosynthesis really is? As plants grow, they breathe in carbon dioxide and store that carbon in their fibers. Incredible carbon capture technology is all around us. Left in a forest, however, the tree will eventually decompose and the carbon is released back into the atmosphere. This is one of the reasons why using wood in buildings is a beneficial strategy for reducing our carbon footprint. By using wood, we take that stored carbon and lock it away in a building for the life of the structure.
How much carbon is actually in a piece of wood? Well, it depends on the type of wood! Wood is roughly 50% carbon by dry weight. So, figure out the weight and you can easily calculate how much carbon is stored. This WoodWorks article has a full explanation I’d recommend you read. I’ll use their numbers for reference. Let’s look at Douglas fir-larch (DFL)
1 - Every cubic meter of DFL contains 240kg of carbon1
2 - Every cubic meter of DFL stores the equivalent of 880kg of CO2
3 - Every cubic meter of DFL stores the equivalent of driving 3515km (2,184 miles)
Wood isn’t the only material that can absorb and store carbon in its fibers. Any material that is biogenic will sequester carbon and can be used to reduce the carbon impact of your building. Some other great examples are hemp, straw, cellulose, and bamboo. Check out the graphic below to understand how they compare.
THE GRAPHIC
WHY IT MATTERS
Wood matters for three primary reasons:
Less carbon is released to make and modify
Carbon is stored in wood products over the long-term
Wood is renewable, recyclable, and reusable
Let’s dig a little deeper:
1 - Less carbon is released to make and modify
When explaining this concept to people I like to use a very practical example to illustrate this idea. Think about the amount of effort required for you to cut a piece of 2x4 wood in half if you used no power tools. Not too bad with a sharp saw. Think about trying to cut the same piece of steel or concrete. There are some obvious flaws with this comparison but what it illustrates well is the relative softness of wood. As a material it is easy to cut, easy to shape, and easy to manipulate without an absorbent amount of energy.
Energy use is an important factor that makes wood a more sustainable choice. The average glulam has an A1-A3 impact of 137.19kg CO2e/m3 which is much lower than its counterparts.
2 - Carbon is stored in wood products over the long-term
As we discussed in the earlier section, wood stores carbon in it’s fibers and locks it in the building. It actually stores more carbon than it takes to produce, making it a carbon-negative material. This doesn’t remove the carbon from the atmosphere forever, but it does lock it up for 50-100 years.
3 - Wood is renewable, recyclable, and reusable
An obvious fact about wood is that it is renewable. With the right forest management processes, the amount and type of wood we use can be maintained over the long-term. Yes, we need to do better in many places, but Mass Timber allows us to combine younger, smaller trees rather than using old-growth.
Wood is also incredibly recyclable and reusable. Many of the products we use today are actually downcycled wood products that have been put to other uses like creating energy. Wood can also be upcycled into furniture or other elements after it’s original use.
1 TIP - HOW TO REDUCE
There are many obvious areas where wood can be used to reduce the carbon impact of your building. The less obvious, but very effective place is in your curtain walls. Instead of using aluminum extrusions that have a high embodied carbon impact, try swapping them out for wood. You’ll get better energy performance as well. Plus they look a whole lot better IMO.
1 PERSON - TO FOLLOW
Rocky Sethi is a developer and Mass Timber leader in the Vancouver area. He often talks about the challenges and opportunities with Mass Timber in real estate.
1 RESOURCE - TO HELP YOU ACT
If you are going to be working on a Mass Timber project you should take a look at the WoodWorks Mass Timber Cost and Design Optimization Checklists. It is a helpful guide through every phase of a design project.