Why Prioritizing EPDs Over Operational Efficiency is a Missed Opportunity

There are two types of carbon that are important when designing and constructing buildings: embodied carbon and operational carbon.

Reference: Environmental Product Declarations: EPDs provide a robust, science-based communication method for demonstrating the environmental credentials of products and services.

Embodied carbon refers to the carbon emissions associated with the materials used in construction—everything from the production of concrete to the transport of windows.

Operational carbon, on the other hand, is the carbon emitted over a building’s lifetime—through heating, cooling, lighting, and ventilation.

Lately, the spotlight has been disproportionately on embodied carbon. Why disproportionate? Because, in my opinion, and also backed up by the simple calculations I performed in my recent article “How Important is Embodied Carbon?”, I showed that unless the expected life of a building is less than 20 years, operational carbon is always the biggest contributing factor to a building’s total carbon emissions.

I’m not calling myself an expert in LCA or EPD because, frankly, it’s confusing to say the least. And the recent changes to EN15804 are making it even more so:

The new standard introduced 19 environmental impact categories (up from 7 in the previous version), making the process more detailed but also more complex.
It revamped the handling of biogenic carbon, splitting the Global Warming Potential (GWP) into subcategories like fossil carbon and biogenic carbon. While this provides more clarity, it adds to the complexity.
A key change was the requirement for products to declare their end-of-life scenarios and account for recycling and reuse (Modules C and D), making the process more comprehensive.

This new level of detail is important, but it also makes the EPD process increasingly difficult to manage. In some areas, it’s simply incorrect because we don’t have all the data (especially around biogenic carbon for timber). As a result, manufacturers and designers must constantly keep up with the evolving rules and methods.

Moving Goalposts

While embodied carbon is important, it’s essential to remember that it’s a one-time impact—it occurs during the construction phase. Once the building is up and running, its operational carbon footprint becomes the primary contributor to emissions, often lasting for decades. This is where the bulk of carbon emissions come from over the building’s lifecycle.

And guess what? We don’t need to wait for the next big innovation to reduce operational carbon—we already have proven tools in hand. Passive House standards offer a clear, achievable path to drastically cut operational energy use, with a remarkable track record of success.

Passive House design is a comfort target with focus on minimizing energy consumption through superior insulation, airtight construction, and optimized ventilation. By reducing the need for active heating and cooling, Passive House buildings achieve remarkable reductions in operational carbon over their lifetime. And this can be done with materials and technologies that are available right now—no waiting for the next EPD update or an elusive material breakthrough.

In contrast, Life Cycle Assessments (LCA) and the pursuit of constantly changing EPD standards can feel like chasing a moving target. The complexity involved in calculating and re-calculating embodied carbon, while valuable, often outweighs the long-term benefits it provides. The process of LCA is no less intense than Passive House modelling and certification, yet it focuses on a smaller slice of the building’s carbon emissions.

And there’s also the issue that high-carbon materials like steel, concrete, and glass are now penalized in these assessments. While these materials undeniably have higher embodied carbon, they are also key players in optimizing a building’s durability, comfort, and operational performance. This focus on punishing high-carbon materials distorts our ability to take a balanced approach to building design.

Carbon villains of building materials

While steel, concrete, and glass are now villainised for their embodied carbon, they also offer incredible benefits when used properly. They are crucial to creating buildings that are not only durable and comfortable, but also energy-efficient in the long run.

Steel is incredibly strong and durable, allowing for slender structures that use less material while providing robust integrity. In combination with exterior insulation and airtightness, steel-framed buildings can achieve low operational energy demand, making it a key material in sustainable, long-term construction. This type of construction offers massive thermal bridge free design options making Passive House Certification very easy.
Concrete is often maligned for its carbon footprint, but it offers excellent thermal mass, which helps regulate indoor temperatures. Although most people understand concrete to be absorbing heat during the day to release it at night – it is actually much more effective to manage cooling – by maintaining indoor temperatures throughout the day – provided it is sheltered properly from sunlight. This makes concrete an asset in buildings aiming for energy efficiency and thermal comfort.
Glass can also be a misunderstood material. Modern glazing technologies, including triple glazing, low-emissivity coatings, and thermally broken frames, significantly improve the insulation properties of glass. When strategically placed, glass can optimize natural light and passive solar heat gain, reducing the need for artificial heating and lighting, thereby supporting operational efficiency.

Focusing on operational efficiency through proven methods like energy modelling, airtightness, and balanced mechanical ventilation offers a far more impactful approach for reducing a building’s overall carbon emissions. By optimizing for comfort, we automatically reduce operational carbon.

Wikipedia Environmental Product Declaration Page

Building Science: Thermal Mass and Insulation’s Roles Explained

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