Mass Timber - The dirty secret

* The basis of this article is from Mass Timber through a Life Cycle Lense by Kelly Doran in the Canadian Architect on June 1, 2022. View the full article here.

Changing Perspectives

The focus on carbon reduction in buildings is shifting. Although still a critical factor, operational carbon is beginning to take a back seat to embodied carbon as buildings see increased use of electricity and a continued push towards greener grids. This is a welcome change as embodied carbon remains largely unregulated despite its significant contributions to the climate emergency.

A Starting Place

Embodied carbon is a relatively new topic and has yet to have well-established benchmarks, although they are in the works. For example, Ha/f Studio out of the University of Toronto is currently developing an embodied carbon benchmark for Part 3 buildings in Ontario. As part of this benchmarking process, the team performed detailed Life Cycle Assessments of two city-owned projects. Since both projects were in late design stages, targeted material specifications were recommended to the design teams to reduce their embodied carbon.?

Incredibly, the team recommended 6 improvements to the project that would reduce upfront carbon emissions WITHOUT requiring significant redesign or additional construction cost.

You read that correctly. 25% embodied carbon reduction. No additional cost or significant design change.

25% embodied carbon reduction. No additional cost or significant design change.

The strategies, in order of CO2e reduced, included:

> Lower carbon concrete

> Lower impact XPS insulation

> Lower impact concrete slab sealant

> High recycled steel content

> Hempcrete block

> Recycled glass gravel insulation

* Embodied carbon reduction strategies by TCO2E. Image from Canadian Architect.

Mass Timber

Building on the understanding that materials matter, Ha/f Studio focused its attention on Mass Timber and surprisingly did not see the benefits of Mass Timber on reducing the embodied carbon of the building unless biogenic sequestration (a controversial topic) was taken into account. In fact, they found the embodied emissions of timber buildings were near equal when factoring the types of building into the equation.?

What does that mean? Well, basically just because your building is Mass Timber doesn’t make it low in embodied carbon. The focus still needs to be taken to look at all the other materials in a building to reduce impacts.?

When biogenic storage was accounted for, roughly a 40% decrease in carbon was achieved in principle. However, what we will see in the next section is the unfortunate reality that not all timber is the same.?

In fact timber, just like many other materials, it depends highly on where it is from and how it is processed.?

Geography Matters

The final conclusion coming out of the Ha/f Studio research is the importance that location plays in the true global warming potential of Mass Timber. Specifically from transportation.

For example, only 1 of 4 of the mass timber projects referenced by the Studio used wood sourced from Ontario. The remainder came from overseas or western North America, contributing significantly to the total carbon of the building as transportation across the country is still heavily carbonized.

This reveals two important factors when looking at Mass Timber.?

1. Location - Where is the wood from?
2. Processing - Where is the wood processed?

Let's take a closer look at those two in more detail.

Location?

Location matters because of the heavily fossil fuel-driven transportation required to process, mill, and ship wood products. Wood shipped across the country will quickly lose its embodied carbon benefits if trucked 4,300kms.?

Processing

Processing matters because of the power grid makeup in different regions. Washington and BC have a well-known clean grid, whereas our neighbors to the east emit approximately 8 times the carbon.?

An Alberta plant contributes 8 times more carbon than one in Washington.

* Timber manufacturing locations vs project locations. Image from Canadian Architect.

Conclusion

So what are the key points here??

1. Materials matter. Whether you are specifying wood or concrete, BOTH need to be reviewed from a carbon perspective and understand how the materials you specify will impact the bottom line.?
2. Reduction doesn't need to be expensive. There is a misconception that reducing your carbon footprint will cost more money. That is simply not true as we see how simply specifying a material that is more regionally available could reduce its GWP significantly.
3. Wood is AN answer. Although wood has problems, it is a great solution to carbon reduction in buildings. Using it generously will only increase its popularity and available resources for future projects.

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