Beyond Net-Zero: How Carbon-Storing Materials Redefine Building Performance

The green building movement has made remarkable strides in reducing operational energy use, but the next challenge is clear: embodied carbon. Even a net-zero energy building can have a significant carbon footprint from the materials used in its construction. Carbon-storing materials offer a paradigm shift—they can sequester carbon dioxide during their growth or production, locking it away for the life of the building. This guide moves beyond the net-zero energy conversation to explore how these materials redefine building performance, addressing the practicalities of specification, cost, and long-term carbon accounting.

Why Carbon-Storing Materials Matter Now

The urgency to address embodied carbon has never been greater. According to many industry analyses, embodied carbon now accounts for roughly half of total building-related emissions over a typical building's lifespan, and this share is growing as operational efficiency improves. Traditional materials like concrete and steel are responsible for a large portion of these emissions. Carbon-storing materials—such as timber, bamboo, hempcrete, and straw bales—offer a way to reverse the flow, turning buildings into carbon sinks rather than sources. The mechanism is straightforward: plants absorb CO2 during photosynthesis, and when used in construction, that carbon remains stored as long as the material is intact. This biogenic carbon storage can significantly offset the emissions from other building components. For example, a mid-rise building using cross-laminated timber (CLT) can store hundreds of tons of CO2, effectively making it carbon-negative when considering the biogenic carbon. However, the devil is in the details: the carbon storage is only permanent if the material is protected from decay, fire, or demolition. This section sets the stage for understanding why carbon-storing materials are not just an environmental nicety but a strategic imperative for meeting climate targets.

The Carbon Accounting Challenge

One of the biggest hurdles is how we account for biogenic carbon. Current life-cycle assessment (LCA) methods vary widely. Some standards treat biogenic carbon as neutral (assuming the carbon released at end-of-life equals what was absorbed), while others credit it upfront. This inconsistency can lead to confusion when comparing materials. Teams must be clear about the methodology they use and communicate assumptions transparently. A growing consensus favors dynamic LCA that accounts for timing—carbon stored now is more valuable than emissions avoided later because we need to reduce atmospheric CO2 urgently.

How Carbon-Storing Materials Work: Mechanisms and Trade-offs

To make informed decisions, it helps to understand the three main mechanisms by which materials store carbon: biogenic sequestration (plants), mineral carbonation (reactions with CO2), and bio-based binders (replacing carbon-intensive cement). Each has unique performance characteristics, cost profiles, and limitations. Biogenic materials like timber and bamboo are renewable and store carbon from the atmosphere, but they require careful forest management and may have lower structural capacity than steel or concrete. Mineral carbonation, used in some carbon-negative concrete products, captures CO2 from industrial sources and locks it into calcium carbonate, but the technology is still scaling and can be expensive. Bio-based binders, such as hempcrete or mycelium composites, offer insulation and carbon storage but often need structural support from other materials. The table below compares three common carbon-storing material categories.

Performance Beyond Carbon

Carbon storage is not the only benefit. Many carbon-storing materials also offer superior thermal performance, humidity regulation, and acoustic properties. Hempcrete, for instance, has a high thermal mass and can buffer indoor humidity, improving occupant comfort. CLT provides a warm aesthetic and can reduce construction time due to prefabrication. These co-benefits can justify the material choice even without carbon credits. However, teams must also consider durability: biogenic materials are susceptible to moisture, pests, and fire if not detailed correctly. Proper design and maintenance are essential to ensure the carbon remains stored for the building's life.

Practical Steps for Specifying Carbon-Storing Materials

Integrating carbon-storing materials into a project requires a shift in mindset and process. Here is a step-by-step guide based on what teams often find effective.

1. Set Carbon Targets Early: Define embodied carbon reduction goals during the pre-design phase. Use tools like whole-building LCA software to establish a baseline and track progress.
2. Evaluate Material Availability: Not all carbon-storing materials are available everywhere. Check local suppliers for CLT, hempcrete, or other products. Consider the carbon impact of transportation—a material shipped from far away may negate its storage benefits.
3. Engage Structural Engineers Early: Carbon-storing materials often have different structural properties. For example, CLT is lighter than concrete but requires careful connection detailing. Early collaboration avoids costly redesigns.
4. Plan for Moisture Management: Biogenic materials need protection from moisture during construction and occupancy. Design for drainage, vapor control, and regular inspections.
5. Document Carbon Storage: Use environmental product declarations (EPDs) and third-party certifications to verify carbon claims. Keep records for future carbon accounting or certification systems like LEED or Living Building Challenge.
6. Consider End-of-Life: Design for deconstruction so that materials can be reused or recycled, preserving the stored carbon. Avoid composite assemblies that are hard to separate.

Common Pitfalls in Specification

One frequent mistake is assuming all timber products are carbon-storing. The carbon benefit depends on the source—timber from sustainably managed forests that regrow is beneficial, while timber from deforestation can have a net positive emissions impact. Similarly, some bio-based products may use fossil-fuel-intensive processing that offsets the carbon storage. Always request EPDs and verify the supply chain. Another pitfall is ignoring the carbon footprint of fasteners, sealants, and other ancillary materials. A CLT building still needs steel connections and insulation; these should be included in the LCA.

Economic Realities and Market Trends

The cost of carbon-storing materials varies widely. CLT can be competitive with steel and concrete for mid-rise buildings, especially when considering faster construction time and reduced foundation costs. Hempcrete often has a higher material cost but lower labor cost for insulation because it is applied in place. Carbon-negative concrete may carry a 10–20% premium, but prices are falling as production scales. Many regions offer incentives for low-carbon materials, such as tax credits or grants. Additionally, the social cost of carbon—if internalized—can make these materials financially attractive. Teams should perform a total cost of ownership analysis that includes operational energy savings, potential carbon credits, and future regulatory costs. The market is growing rapidly: many industry surveys suggest that the global market for biogenic building materials could double in the next five years, driven by policy and corporate sustainability commitments.

Insurance and Liability Considerations

Some insurers still view novel materials as higher risk, which can lead to higher premiums. However, as more data on performance becomes available, this is changing. Teams should document design decisions and seek insurers with experience in green building. In some cases, using carbon-storing materials can reduce risk by improving indoor air quality and occupant health, which may lower liability over time.

Scaling Adoption: Overcoming Barriers

For carbon-storing materials to become mainstream, several barriers must be addressed. Supply chain maturity is a key issue: many materials are produced by a small number of manufacturers, leading to long lead times and higher costs. Investment in local production facilities can reduce transportation emissions and create jobs. Another barrier is code acceptance. Some building codes have not yet adopted provisions for mass timber or hempcrete, requiring project-specific approvals. Advocacy and participation in code development can help. Education is also critical—architects, engineers, and contractors need training on design and installation. Many professional organizations now offer courses on biogenic materials. Finally, digital tools for LCA need to improve to accurately model carbon storage and end-of-life scenarios, making it easier for teams to compare options.

Role of Policy and Certification

Government policies, such as Buy Clean programs and embodied carbon limits, are accelerating adoption. Certification systems like LEED v5 and the Living Building Challenge now reward carbon storage explicitly. Teams should align their material choices with these frameworks to maximize recognition and potential incentives. However, be cautious of greenwashing: some products claim carbon storage based on dubious accounting. Third-party verification, such as from the Carbon Leadership Forum or similar bodies, adds credibility.

Risks, Pitfalls, and How to Avoid Them

While carbon-storing materials offer immense potential, they are not a silver bullet. One major risk is carbon reversal—if the material burns, decays, or is landfilled, the stored carbon is released. Proper design for fire safety, moisture control, and end-of-life is essential. Another risk is the rebound effect: using more material than necessary to achieve carbon storage can increase other environmental impacts. Teams should optimize the design to use materials efficiently. There is also the risk of unintended consequences, such as land-use competition for biomass production. Sourcing from certified sustainable sources helps mitigate this. Finally, be aware of performance trade-offs: some carbon-storing materials have lower strength or durability than conventional options, requiring careful detailing. For example, hempcrete is not suitable for load-bearing walls and needs a structural frame. A balanced approach is to use carbon-storing materials where they are most effective (e.g., CLT for structure, hempcrete for insulation) and conventional materials where performance demands are highest.

Decision Checklist for Your Next Project

• Have we set embodied carbon targets early in design?
• Are local suppliers available for the chosen material?
• Have we verified carbon storage claims with EPDs?
• Is the design protecting the material from moisture and fire?
• Have we considered the end-of-life scenario for carbon permanence?
• Does the total cost of ownership account for incentives and future carbon pricing?
• Are we engaging with insurers and code officials early?

Frequently Asked Questions

How long does carbon stay stored in building materials?

As long as the material remains intact and not burned or decomposed. For timber in a well-maintained building, that can be 50–100 years or more. Design for deconstruction can extend storage through reuse.

Can carbon-storing materials compete with concrete and steel on strength?

For many applications, yes. CLT can be used for mid-rise structures up to 10–12 stories. However, for very tall buildings or long spans, steel and concrete may still be needed. Hybrid designs are common.

Are carbon-storing materials more expensive?

It depends. CLT can be cost-competitive when considering speed of construction. Hempcrete may have a higher upfront cost but lower energy bills. Carbon-negative concrete is currently more expensive but prices are dropping. A whole-life cost analysis is recommended.

How do I verify that a product truly stores carbon?

Look for third-party verified Environmental Product Declarations (EPDs) that include biogenic carbon data. Also check for certifications like Cradle to Cradle or FSC for timber. Be wary of products that claim carbon storage without transparent methodology.

Taking Action: Your Next Steps

Carbon-storing materials represent a transformative opportunity for the building industry to move beyond net-zero energy and become climate-positive. The path forward involves education, collaboration, and a willingness to challenge conventional practices. Start by conducting a whole-building LCA on your current project to understand your embodied carbon baseline. Then, identify one or two carbon-storing materials that are viable for your region and project type. Engage with suppliers, attend training, and pilot the material on a small scale. Share your lessons learned with the broader community to help build the evidence base. The transition will not happen overnight, but each project that incorporates carbon-storing materials moves the industry closer to a regenerative future. As more data becomes available and supply chains mature, these materials will become the new normal. The question is no longer whether we can afford to use them, but whether we can afford not to.