It’s a striking building.
If, over the past year or so, you’ve driven up Broadway toward Central Market, you may have noticed the big office building going up at Broadway and 8th Street. Ordinarily, it’s no big deal seeing another office building going up in downtown. But this one has been hard to miss. It is being built with enormous, beautiful, structural wood.
It is out of the ordinary, and maybe you’ve wondered about it.
That building — The Soto — is the first “mass timber” office building in Texas. Yes, it’s a 6-story building constructed of wood, and it might be the start of a trend.
The Soto -- the first "mass timber" office building in Texas
We’re all pretty familiar with common methods of cutting back on greenhouse gas emissions in our homes and offices — we know we can install better insulation, use LED lighting, and generate power using solar panels.
Those practices reduce what we in the industry call “operational carbon” — that is, the greenhouse gases that are generated from operating our buildings.
Something that you are probably less familiar with is “embodied carbon” — the greenhouse gases that are emitted when we construct those buildings. Embodied carbon is emitted when we manufacture steel, when we ship the steel, when we pour the concrete, and so on. Yes, embodied carbon contributes less than operational carbon to the enormous amount of greenhouse gas emissions associated with building construction. But, the impact of embodied carbon is growing.
The best decision we can make for reducing embodied carbon in buildings is to reuse existing buildings. Our neighborhood is already doing a great job of preserving historic structures, thereby eliminating the embodied carbon associated with replacing buildings every 30 years or so. But when we are constructing new buildings, what decisions will have the greatest impact on embodied carbon? If we look at a breakdown of what impacts embodied carbon emissions, we see the materials we select for the superstructure are a significant contributor.
Most commercial building structures are made of concrete or steel, which are both very carbon intensive materials. Wood is a lower embodied carbon alternative to these materials.
First, let me explain what we mean by “mass timber.” It’s not the same thing as boards sawn from a tree. Mass timber is a code-approved subset of wood construction that is made up of large wood members — larger than the wood members that are typically used in residential buildings. Modern mass timber uses smaller dimensional lumber bonded together into larger components. There are a few types. Glue-laminated (glulam) elements are used for columns and beams. Cross-laminated timber (CLT) panels are often used for walls, floors, and roofs. And other variations, like nail- and dowel-laminated timber (NLT and DLT) and mass-plywood are being used and show promise.
Mass timber does more than provide environmental benefits and durable performance: It’s also beautiful! The Soto’s mass timber structural system was deliberately exposed on both the building’s exterior and interior to express the natural beauty of wood. This natural aesthetic has been proven to have a strong positive impact on human health, well-being, and productivity.
As mentioned earlier, building with mass timber results in less construction time, lower costs, and less construction noise — all important factors when building on an infill site in a dense urban neighborhood. Mass timber buildings are really lightweight when compared to conventional tall steel and concrete buildings. This allows for smaller foundations, which results in savings in both construction cost and schedule. Mass timber buildings result in shorter construction schedules because the products are prepared off-site reducing the need for material preparation and staging. This saves on not just time and labor costs, but construction noise as well.
Eliminating the use of concrete in building roof and floor assemblies significantly shortens the construction time of mass timber buildings, since the concrete curing time is eliminated. In exposed mass timber buildings, there are also noteworthy cost savings from reduced construction assemblies (gypsum board, paint, etc.) in the exposed portions. Though material costs vary widely depending on location and timing, locally sourced timber products are not subject to tariffs, which also results in cost savings.
An interior view of the Soto that highlights its wood structure.
“Soto” is the Spanish word for a grove of trees or small forest. It’s the perfect name for the building as it represents the building’s material and its commitment to sustainability.
The building is a unique and beautiful workplace that appeals to tenants, is highly flexible, and incorporates technologies that make it operationally efficient and sustainable. The Soto’s owner and the design and construction teams chose mass timber as the building’s primary structural material because it promotes sustainability, fosters human health and productivity, and reduces construction time and noise — a big benefit in dense urban areas where you want to minimize construction disturbances to residents!
Interior shots of The Soto
Unlike concrete and steel, mass timber is renewable when harvested responsibly and sustainably. There’s still some research to be done, but with responsible forest management, wood as a building material will never be depleted. Additionally, trees capture and store carbon dioxide from the atmosphere as they grow, making mass timber a carbon sequestering material.
And, as we’ve seen for some time now, the supply chain is extremely volatile. The lead times for obtaining conventional steel and concrete building materials can be much longer than for obtaining mass timber.
We are so used to seeing commercial buildings made of steel and concrete that we’ve probably assumed that those materials are the only choices for large construction. We might reasonably have assumed that timber isn’t strong enough for non-residential building. Or that it’s not fire-safe. We might even have assumed that cutting timber for buildings is bad for the environment.
And we would have been wrong.
Substituting mass timber for concrete and steel has environmental, design aesthetic, human health, and construction impact benefits, showing promise for applications in historic, urban neighborhoods like ours.
Heather Holdridge is the Sustainability Director at Lake | Flato Architects
Maybe there's a better way?
Thursday, September 15, 2022
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