27 August 2025 – The buildings and construction sector is responsible for roughly one-third of global carbon emissions and waste[1],[2]. This raises a critical question: How do we ensure that both new and existing buildings reduce negative impacts while meeting growing demands? In this blog, Rupert Jordi, CISL Programme Manager, explores 'green' buildings, warns against conflating building certification with true sustainability, and argues the label is less important than the outcomes.
As an architect and educator committed to delivering a sustainable built environment, I’m buoyed by an increase in circular construction, green building certification and the reuse of existing buildings [3], and I celebrate the growing social acceptance and demand for green credentials. However, despite this progress, I’m concerned by projects that exploit this demand for sustainable buildings and worry that an overemphasis on green certification distracts from delivering truly sustainable outcomes.
What is a ‘green building’?
To some, ‘green building’ is synonymous with ‘sustainable building’. Both terms have many connotations and may be perceived as ranging from greenwashing to a genuine attempt to address critical challenges. Others may find these terms idealistic or unfounded, or worry that other financial or practical outcomes are deprioritised in favour of ‘green’ features. Neither has a universal definition, though, and to many, ‘green building’ refers specifically to certified projects. Broadly speaking, a ‘green building’ should be a systems approach to design, procurement, construction, and operation that minimises the environmental impact of the built environment, improves social outcomes, protects and restores nature, and promotes circularity and resource efficiency throughout a building's lifecycle. It calls for regulation and certification to incentivise positive change across the sector and requires collaboration between public and private organisations and disruptors to innovate and increase the pace and scale of change.
The focus of this definition is on a systemic market shift toward sustainable buildings and infrastructure, and the individual and collective actions needed to achieve it.
Green buildings and certification
Green building certifications – although varied – share a common goal: to measure and improve sustainability performance.
Green certification as we know it today emerged in the 1990s, with the launch of the BREEAM assessment framework in 1990, followed shortly by the LEED rating system. Since then, many other councils and initiatives have developed their own frameworks, each with different emphases.
These have helped drive progress, particularly in energy efficiency and carbon reduction. But they also reflect a narrow, carbon-centric view of sustainability — one that often overlooks broader social and ecological concerns. While some promote water and resource conservation or improved air quality, they tend to focus on individual buildings, rather than the surrounding urban fabric, and often fail to account for regional differences.
The evolution of certification
The World Green Building Council (WGBC) says, “Any building can be a sustainable building, but not all sustainable buildings are the same. Different countries and regions have distinctive climatic conditions, unique cultures and traditions, diverse building types and ages, or wide-ranging environmental, economic and social priorities.[4]”
The WGBC’s 2025 strategic plan spans markets and geographies and seeks to:
- Ensure healthy, equitable and resilient buildings, cities and communities.
- Regenerate natural systems.
- Accelerate the sustainable and just transition of the built environment.[5]
This contemporary framing reflects a significant shift toward a systems-based approach. But certification alone is not enough!
Beyond certification: The Entopia Building
Approximately 40% of 2050’s global building stock exists today[6]. Improving the sustainability of existing buildings is crucial to delivering a sustainable built environment, with many green building councils focusing efforts on green retrofits.
Similarly, when CISL designed its new home, the Entopia Building, it compared a retrofit with building from scratch and found that “a newly constructed building, including demolition of the existing structure, would likely generate between 970–1,620 kgCO₂e/m². In contrast, a deep retrofit would generate 400 kgCO₂e/m²” — or 50–75% less carbon compared to building anew.[7]”
CISL also recognised that no single certification was enough; that to demonstrate innovation and a truly sustainable retrofit, it needed to target as many ambitious certifications as possible. In a world-first, it achieved BREEAM (Outstanding), Passivhaus “EnerPHit” Classic and WELL Gold. But, more importantly, these all rest on circular design principles and long-term resilience.
Today, the Entopia building acts as a Living Lab, providing an open innovation platform to accelerate the adoption of solutions and innovations in the built environment.
"We want to show that sustainability in the built environment is not just the right thing to do but also makes strong business sense." – James Cole, Chief Innovation Officer at CISL.
Building your green perspective
- Instead of relying on energy-intensive ventilation and lighting, it utilises passive design.
- Its functions are adaptable and can change over time.
- It is designed for disassembly to avoid waste.
- It regenerates local ecosystems through land and water restoration programmes.
We teach these and other principles in CISL’s Sustainable Real Estate online short course, as we explore what it takes to deliver a truly sustainable built environment.
The future of green building
Certification and voluntary standards have a role to play, but as CISL argues, they’re not enough: we need policy and mandatory measures to support sustainable real estate.
Equally, we must apply systems thinking when determining whether a building contributes positively to its occupants, the environment, and society more broadly.
We must be cautious of greenwashing that uses green labels to attract investment. And while green certification has helped grow the market for sustainable construction materials, we risk falling into the same trap of overconsumption that drives so many of the world’s biggest sustainability challenges.
Ultimately, we must not conflate true sustainability with certified green performance metrics. The label ‘green building’ and certification matter less than the outcomes do, and there’s a real risk that we become complacent in the belief that ‘green buildings’ will solve the sector’s problems.
"We must not conflate true sustainability with certified green performance metrics. The label ‘green building’ and certification matter less than the outcomes do." – Rupert Jordi, CISL Programme Manager
Whether you’re an investor interrogating what lies beneath green premiums, an architect designing sustainable spaces, an engineer grappling with new ‘green’ materials, or a prospective buyer trying to understand the market for sustainable buildings, CISL’s Sustainable Real Estate online short course will help you explore the challenges and opportunities in the sector.
CISL’s latest initiative, ‘Transforming Systems, Sectors and Places,’ highlights the importance of the built environment in the green transition.
Discover more about CISL’s Entopia Building and its Living Lab project.
References
[1] United Nations Environment Programme (2025). Global Status Report for Buildings and Construction 2024/2025: Not just another brick in the wall - The solutions exist. Scaling them will build on progress and cut emissions fast. Paris.
[2] United Nations Environment Programme (2024). Global Status Report for Buildings and Construction: Beyond foundations: Mainstreaming sustainable solutions to cut emissions from the buildings sector. Nairobi.
[3] UNEP, 2025 (ibid).
[4] World Green Building Council (2025). What is a Sustainable Built Environment? Available: https://worldgbc.org/what-is-a-sustainable-built-environment/
[5] World Green Building Council (2025). WorldGBC strategic plan 2025-2027. Accessible: https://worldgbc.org/strategic-plan-2025-2027/
[6] UNEP, 2024 (ibid.)
[7] Cambridge Institute for Sustainability Leadership (CISL). n.d.a. Building Entopia: The story behind the ultra-sustainable retrofit of CISL’s new home in Cambridge. Available: https://www.cisl.cam.ac.uk/about/entopia-building
