Why Does It Matter?
So, what impact does the construction industry have on the environment? Well, the emissions from construction contributed around 10% of total global energy-related CO2 emissions in 2020 (1) - with concrete particularly responsible. This substance, made up of sand, aggregate, cement, water, and chemical additives, is a primary building material and hit a production mark of 4.2 billion tons in 2016. As the largest producer of non-energy-related industrial carbon emissions, every ton of cement created produces 0.5 t of CO2 (2). Concrete and steel are the primary building materials for mid and high-rise residential buildings, but this can be changed.
What Can We Do?
We likely can't discard the use of concrete altogether since it is used in a lot of infrastructure in the United States and the world. However, we could consider replacing a few of the uses of concrete with better materials, particularly for the construction of multi-story housing. Mass Timber is one such material that has been demonstrated to exceed the carbon emissions and global warming potential (GWP) of steel and concrete structures.
Mass Timber Considerations
It's essential to remember that Mass Timber isn't an alternative for all aspects of concrete and steel (like foundations and footings). It covers specific applications, and reduces the total amount used in a project. Also, the International Building Code only recently approved elements of Mass Timber to be exposed internally on particular types of vertical structures. Before these regulations were put in place, Mass Timber had to have extra layers of fire protection integrated into the design. This could involve plasterboard around the timber (fireproofing) or thicker mass timber components (char layer). Most of the figures cited hereafter will not reflect these beneficial changes because they are so recent. That being said, let's explore three of Mass Timber’s eco-friendly features: carbon sequestration/emissions, weight reduction, and the ability to source building materials locally.
Co2 Emissions and Storage
First, many cradle-to-grave studies have compared Mass Timber with concrete and steel buildings. Results showed that Mass Timber buildings had GWP and carbon emissions that were up to 41% less than their steel substitutes and 26% less than concrete alternatives (2). Moreover, when factoring in carbon sequestration, these buildings were almost entirely carbon neutral (3). Mass timber can store up to three times more carbon than concrete and steel, thereby keeping the greenhouse gasses out of the atmosphere. One study, comparing mass timber to concrete buildings, found that an extra 1,556t Co2 and 2,567t Co2 can be stored in the timber components of the building (long-term storage of biogenic carbon) even when fireproofing with drywall and char layers, respectively (2).
Second, Mass Timber is much lighter than either concrete or steel. And as mentioned above, Mass Timber doesn’t replace concrete in all building aspects, but it changes the form and quantity. This is particularly applicable for vertical construction and the structural requirements for foundations, piles, and piers. Timber buildings are lighter than their concrete or steel alternatives, so those foundations can be smaller, reducing the amount of concrete used and therefore the environmental impact.
Weight reduction isn’t the only factor that determines the foundation requirements for a building, but it certainly is a big one. Ricky McClain with the Mass Timber How To’s YouTube channel does an excellent job at explaining this in detail.
Continuing, weight reduction also reduces the emissions associated with material transport, but only if the Mass Timber components are locally sourced. If Mass Timber components are trucked extremely long distances, the carbon offset of the material can be completely negated. This is an important aspect to consider when working with different manufacturers and is often overlooked. As more and more Mass Timber manufacturing plants are built, this becomes less of a concern. Yet, some areas of the county remain a significant distance away from both the raw material fiber (logable forests) and the production plants. One study found that manufacturing facilities can achieve up to 14% reduction in the overall GWP of the Mass Timber by sourcing the lumber locally and using lighter wood species (4).
In conclusion, the construction industry has a significant impact on the environment, with the emissions from concrete being one of the largest contributors to energy-related CO2 emissions globally. However, Mass Timber has been shown to be an eco-friendlier alternative to concrete and steel, with lower carbon emissions and global warming potential, as well as greater carbon sequestration capabilities. Mass Timber is also lighter than concrete and steel, which reduces the environmental impact of concrete building foundations and reduces the emissions associated with material transport. To fully realize the environmental benefits of Mass Timber though, it’s essential to consider the local sourcing of materials, as well as the potential use of lighter wood species.