Mass Timber Goes Cradle-to-Cradle in Virginia's Apex Plaza

A dozen or so years ago, architect William McDonough and chemist Michael Braungart tried to apply their Cradle-to-Cradle (C2C) concept to buildings, with a charter listing guiding principles including:

• Incorporate materials that are technical and biological nutrients that can become safely reusable nutrients.
  
• Measurably use renewable energy. Examples of renewable energy include solar thermal, ground-based and air-based heat-exchange, wind, biomass, hydro, and, photovoltaic.
  
• Anticipate evolution and change, incorporating strategies and approaches that enhance the ability for the building to adapt to a variety of uses over time.
  

Not much came of the Cradle-to-Cradle charter, but the Apex Plaza—a 187,000 square foot mixed-use building in Charlottesville, Virginia, designed by William McDonough + Partners—demonstrates these principles haven't been forgotten. And, in fact, the principles have been expanded into what they call The Five Goods:

• Good Materials: Including mass timber and low embodied carbon choices.
• Good Economy: A design for adaptability and disassembly.
• Good Energy: All-electric and net positive with a 436-megawatt hour of solar on the rooftop canopy, high-performance glazing, and high-performance rain-screen cladding.
• Good Water: Captured stormwater reused in the landscaping.
• Good Lives: Biophilia, "beauty from simplicity," rooftop landscaping, and views.

The carbon footprint of buildings is the architectural issue of our time, and design partner Alastair Reilly shared a document with Treehugger that shows how they categorize the various types of carbon emissions, including the upfront carbon—I love that they use upfront so prominently—emitted during the product and construction stage and the operating carbon that comes from running the building. But they also put a big emphasis on the end-of-life carbon and actually go beyond the lifecycle with recovery and reuse.

That's one of the reasons this building is so interesting. It's not just being pitched as another big mass timber building. Though it has some of the biggest and chunkiest mass timber we have seen on Treehugger, there's way more going on.

There are many benefits to using mass timber, including speed of construction and reduced mass. But the big one is the lower upfront carbon emissions, as can be seen in this comparison of concrete and mass timber construction. The use of wood results in avoided greenhouse gas emissions of 809 metric tons of carbon dioxide (CO2) compared to building with concrete, which would be a lot bigger if there wasn't such a big chunk of upfront carbon in the concrete podium and multi-level parking garage.

When asked why there was so much parking and why a portion of it was above grade, Reilly told Treehugger the site had previously been surface parking for a neighboring building, and that lost parking had to be accommodated as well as the legal parking requirement for the new space. Reilly noted they did ask for the parking requirement to be reduced, but the request was rejected. However, the parking is designed with ramps on the exterior and with flat parking decks so it can be converted to other uses in the future.

Can a Building Be Carbon Positive?

Reilly's document also claims the building is going "beyond zero carbon and toward carbon positive."

"Carbon sequestration is an important component of building with Cross-Laminated Timber. Forests act as a carbon 'sink' as healthy trees remove carbon dioxide from the atmosphere, release oxygen and sequester/store carbon. Using sustainably harvested FSC mass timber reduces the carbon footprint by storing CO2 in the same way a healthy tree would (one cubic meter of timber stores approximately one ton of CO2)."

They go on to claim that 2,091 metric tons are stored in the wood and 809 metric tons avoided by not using concrete, totaling 2,990 metric tons of potential carbon benefit. This is controversial, almost suggesting the carbon storage offsets the concrete when the trees were doing a fine job storing carbon when they were standing in the forest. Some, like Paula Melton of BuildingGreen, note that "a lot of carbon in forests is stored in the soil and below it, and it’s unclear how much carbon and methane (a more potent greenhouse gas) is released when harvesting."

As engineer Will Hawkins wrote in "Timber and Carbon Sequestration," "accounting for sequestered carbon is often a source of debate, confusion, and inconsistency. When sequestration is reported within Module A, [in the upfront carbon] or alongside it as a negative emission, it can create the counterintuitive impression that using timber excessively can have environmental benefits."

This is why I do not like the term "carbon positive". As Hawkin notes, "It is still better (for the climate) to build nothing at all than a timber building." It is a wonderful thing just to have avoided 809 metric tons of CO2 by changing from concrete; let's not gild the lily.

Design for Deconstruction and Flexibility

The building is designed with mechanical fasteners so it can be disassembled at end of life relatively easily. Reilly is already thinking ahead to the next project, where it will have mechanically fastened cementitious boards for soundproofing instead of the Gypcrete used here.

But disassembly is quite a few years away. The reason most buildings get demolished is they become functionally obsolete. That is less likely to happen here.

One reason that the mass timber is so chunky is that they wanted long spans and a column grid designed for flexibility so it can be adapted to different uses. Reilly shows a typical floor plan laid out for offices, but it is designed so that it can be converted to residential use if the market changes.

The gorgeous exposed mass timber is FSC-certified from Nordic Structures in Quebec and delivered by train. Nordic has the first Cradle to Cradle-certified mass timber products on the market in North America, meaning they are evaluated against criteria including material health, material reutilization, renewable energy and carbon management, water stewardship and social fairness.

McDonough noted that “it is wonderful to see the manufacturers of a product so critical to circular building commit to Cradle to Cradle." He's right; I wish more companies did. Silver is not the highest level of certification, but there were apparently some emissions of VOCs (volatile organic compounds) in the factory itself from the glues before they were completely set.

Mass timber buildings are becoming almost common, and seem only to get attention these days when they are the biggest or the tallest or the weirdest. Apex Plaza is none of these but is certainly among the most interesting because of its design for flexibility, deconstruction, and circularity in the future and because of its net-zero all-electric heating and cooling, solar power, and concern for health and well-being today.

It is also a great example of what I have called my Ironclad Rule of Carbon: "As we electrify everything and decarbonize the electricity supply, emissions from embodied carbon will increasingly dominate and approach 100% of emissions." This is an all-electric building with its energy coming from Apex's renewable supply and the rooftop solar, so pretty much 100% of its lifecycle emissions are going to be coming from the upfront carbon emissions and subsequent embodied carbon emissions.

If you take the position that you shouldn't claim credit for storing carbon in the wood structure—as I do—then the upfront carbon emissions from that oversized parking garage dominate the carbon picture for the project. At 1,445 metric tons of CO2 (shown in the graph above), it is not a small picture.

Now that we have the technology and building codes letting us build low-carbon structures above grade, it is time to get the zoning and planning codes changed to reduce or eliminate that concrete parking. As always, it is the cars that are killing us. You cannot carbon-positive your way out of this with a pile of wood.