For building professionals accustomed to watching carbon emissions climb with every new project, the idea of a building that actually removes carbon from the atmosphere has felt like science fiction. That fiction may soon become code-ready reality. Skidmore, Owings & Merrill (SOM) has spent the past year refining the Urban Sequoia NOW concept, a carbon-absorbing building design that the firm says is buildable today using existing materials and methods. Presented at COP27 in Sharm El-Sheikh, Egypt, the design represents a fundamental shift from additive construction to a reductive, systems-integrated approach that could reshape how building professionals think about carbon in the built environment.
The building sector accounts for nearly 40 percent of global energy-related carbon emissions, and measuring embodied carbon in building construction has become an essential practice for architects, specifiers, and contractors alike. Urban Sequoia NOW proposes a way forward that does not just reduce harm but actively regenerates the environment. Understanding how this carbon-absorbing building design works, what materials enable it, and how it fits current construction workflows is critical knowledge for any professional preparing for the next decade of building performance standards.
The Reductive Construction Philosophy Behind Carbon-Absorbing Building Design
Conventional high-rise construction follows an additive sequence. The structural frame goes up first, followed by the facade, then mechanical, electrical, and plumbing systems, and finally the interior fit-out. Each step adds material, labor, and embodied carbon to the project ledger. Urban Sequoia inverts this workflow entirely.
Systems Integration as Carbon Strategy
The reductive approach consolidates building systems so that every component serves multiple purposes. Instead of hiding air ducts and MEP equipment in ceiling plenums, the design optimises floor slabs to incorporate these systems within the structural depth of the floor itself. By eliminating suspended ceilings entirely, the design achieves higher ceiling heights while using significantly less material. This single change reduces the overall material volume of a typical high-rise by a measurable margin without compromising performance.
The 70 Percent Embodied Carbon Reduction Target
SOM’s calculations show that the reductive construction approach alone reduces upfront embodied carbon by 70 percent compared to a conventional high-rise of equivalent size. This reduction comes from:
- Eliminating redundant ceiling and floor-finished assemblies
- Consolidating ductwork within structural floor depths
- Using exposed structure as the finished ceiling surface
- Integrating ventilation paths into the slab rather than separate duct runs
- Reducing the total volume of concrete, steel, and gypsum board required
For specifiers and quantity surveyors, the implication is clear: carbon-absorbing building design begins not with exotic new products but with smarter assembly configuration. The embodied carbon savings flow directly from how the building is put together.
Carbon-Sequestering Materials That Make Urban Sequoia Buildable
Beyond the reductive construction methodology, Urban Sequoia NOW relies on a palette of materials that actively store carbon or dramatically reduce emissions associated with conventional alternatives. These materials are not laboratory curiosities; they are commercially available products that specifiers can source today.
Mass Timber and Engineered Wood Products
Mass timber sits at the core of the carbon-absorbing building design. Cross-laminated timber (CLT) and glulam beams store carbon that the trees sequestered during their growth cycle, locking it into the building structure for the life of the building. When sourced from sustainably managed forests, mass timber offers a carbon-negative structural solution. The UW Founders Hall mass timber carbon storage project demonstrates how engineered wood products can function as permanent carbon sinks in institutional buildings, a strategy that Urban Sequoia scales to high-rise applications.
Bio-Concrete and Low-Carbon Cement Alternatives
Concrete accounts for approximately 8 percent of global carbon emissions, primarily from the cement manufacturing process. Bio-concrete formulations replace a portion of Portland cement with supplementary cementitious materials such as fly ash, slag, or calcined clays, and in some formulations incorporate carbon-absorbing aggregates or bacterial agents that precipitate calcium carbonate. These bio-concrete mixes reduce the carbon footprint of the structural core while maintaining compressive strength and durability requirements specified in ACI 318 and local building codes.
Energy-Generating Solar Glass and Advanced Glazing
The building envelope in Urban Sequoia NOW uses photovoltaic-integrated glazing that generates electricity while controlling solar heat gain. Advanced solar glass technologies now achieve visible light transmittance suitable for occupied spaces while converting a portion of incoming solar radiation into usable electrical energy. This addresses operational carbon by reducing the building’s reliance on grid electricity, complementing the embodied carbon savings from the structure and finishes.
Material Selection Decision Framework
The following table summarises the primary materials used in carbon-absorbing building design and their key performance characteristics.
| Material | Carbon Impact | Primary Application | Availability |
|---|---|---|---|
| Cross-laminated timber (CLT) | Carbon-negative (stores ~1.1 tCO2/m3) | Floor slabs, shear walls, roof decks | Commercially available N. America & Europe |
| Glulam beams | Carbon-negative (stores ~0.8 tCO2/m3) | Columns, long-span beams, arches | Commercially available globally |
| Bio-concrete | 30-50% reduction vs. standard concrete | Foundations, core walls, transfer slabs | Emerging; select suppliers in EU & NA |
| Solar glass (BIPV) | Offsets 15-25% of operational energy | Curtain wall, spandrel panels, skylights | Commercially available globally |
| Low-carbon steel | 50-70% reduction vs. virgin steel | Connections, reinforcement, decking | Commercially available with EPDs |
Direct Air Capture Integration and the Building Ventilation System
What distinguishes Urban Sequoia NOW from other sustainable building concepts is the integration of direct air capture (DAC) technology into the building’s natural ventilation system. Rather than treating carbon capture as an add-on mechanical system, the building envelope and core are designed to facilitate carbon removal as a core function of daily operation.
Underfloor Ventilation and Sky Garden Air Flows
The design introduces outdoor air through underfloor ventilation openings positioned between the structural slab and a timber floor finish. This low-velocity supply air passes through the occupied floor plate before moving into sky gardens, which serve as both amenity spaces and large air capture zones. The sky gardens are positioned at regular intervals up the building height, creating a vertical sequence of capture chambers where carbon dioxide concentration increases naturally through the stack effect.
The Stack Effect and Core-Based Carbon Capture
As air warms in the sky gardens, it rises through open cavities integrated into the building’s central core. This natural stack effect draws air upward without mechanical fans, reducing the energy penalty typically associated with carbon capture systems. Inside the core cavities, direct air capture technology removes carbon dioxide from the airstream. The captured CO2 is then compressed, stored, and made available for industrial applications, completing the carbon cycle.
The Carbon Removal Economy
SOM envisions Urban Sequoia buildings as nodes in a distributed carbon-removal network. The captured CO2 can feed into multiple industrial streams:
- Carbonated aggregates for bio-concrete production, closing the loop between capture and structural material
- Synthetic fuel production using captured CO2 and green hydrogen
- Greenhouse enrichment for agricultural operations in urban fringe zones
- Beverage carbonation and industrial process gas markets
- Enhanced oil recovery applications where geological storage is the priority
This revenue stream from carbon sales offsets a portion of the building’s operational costs, creating an economic incentive for carbon-absorbing building design beyond regulatory compliance. For developers evaluating the business case, LEED Zero carbon certification standards provide a framework for verifying and reporting the carbon performance that makes these revenue streams credible.
Scalability, Adaptability and the Path to Widespread Adoption
SOM emphasises that Urban Sequoia NOW is not a single building typology but a philosophy applicable at any scale, in any climate, and for any building use. The systems approach adapts to local material availability, climate conditions, and regulatory environments, making carbon-absorbing building design a viable strategy from small commercial buildings to supertall towers.
The 100-Year Performance Window
The design targets three milestone performance thresholds:
- Year zero to five: The building reaches 100 percent whole-life carbon reduction, achieving net-zero status as the carbon absorbed by DAC systems and sequestered in materials offsets all embodied and operational emissions from construction and early operation.
- Year five to 50: The building operates as a net carbon sink, absorbing more carbon annually than it emits through operations, maintenance, and tenant energy use. The cumulative carbon balance becomes increasingly negative each year.
- Year 50 to 100+: Over the full century of intended service life, the building absorbs more than 300 percent of the carbon emitted during its construction and operation. The hybrid mass timber embodied carbon benchmarks from projects like San Mateo County’s COB3 building provide reference data showing that these long-term targets are within reach of current construction practice.
What Building Professionals Need to Do Today
Preparing for carbon-absorbing building design does not require waiting for regulatory mandates. Building professionals can take practical steps now:
- Specify mass timber and bio-concrete on appropriate projects to build supply chain familiarity and contractor experience
- Include embodied carbon tracking in project specifications using tools such as Tally, One Click LCA, or Athena Impact Estimator
- Evaluate project sites for sky garden and natural ventilation feasibility during early design phases
- Engage with direct air capture vendors to understand integration requirements for future projects
- Train estimating and procurement teams to evaluate material costs on a whole-life carbon basis rather than first-cost only
- Review local building codes for mass timber height allowances and fire protection requirements
The transition to carbon-absorbing building design represents one of the most significant shifts in construction methodology since the adoption of curtain wall systems. By combining reductive construction, carbon-sequestering materials, and building-integrated DAC technology, the Urban Sequoia NOW concept offers a playbook that building professionals can begin implementing today. The tools exist, the materials are available, and the performance targets are clear. The question is no longer whether buildings can absorb carbon but how quickly the industry can scale the approach from concept to common practice.
As urban populations grow and the pressure to decarbonise intensifies, the building sector has an opportunity to transform from a net emitter to a net carbon sink. Carbon-absorbing building design, built on reductive construction principles and commercially available materials, makes that transformation possible. For architects, engineers, specifiers, and contractors ready to lead the shift, Urban Sequoia NOW provides a proven framework for building a regenerative built environment.