The new, data-driven reality of sustainable design is shifting the industry’s focus to what can be measured: from the embodied carbon of materials to the verifiable performance of a finished building. This metric-first transformation creates an intricate challenge: accurately capturing, measuring and comparing the environmental impacts of different building products. That’s exactly what the methodology known as Life Cycle Assessment (LCA) can help navigate.

And while many industry professionals are familiar with the term, we ask Caroline Heussner, Sustainability Manager at Knauf Gypsum, to unpack this essential tool in more detail. Here, she explains how LCA can empower architects, designers and specifiers to move from assumption to assurance and make truly informed decisions.

A product’s environmental biography

“Think of LCA as a product’s environmental biography,” explains Caroline. “It examines every single stage of the life cycle of a product: the extraction of raw materials, the energy used in manufacturing, the effects of transportation, the impact during its use and, finally, what happens at its end-of-life – whether it’s disposed of or recycled.”

This holistic view is critical. With buildings accounting for a staggering 39% of global carbon emissions, the responsibility on architects, designers, builders and even investors to mitigate this impact is immense. “They have a key role to play in leading the change towards more sustainable buildings,” Caroline notes. And it’s a responsibility, she adds, that connects directly to our collective goals. “We all want to live in a world with cleaner air, pollution-free environments and a stable climate,” she says. “Those outcomes are all achievable but will require us to make significant changes to our lifestyle and how we interact with the environment.”

By assessing the environmental impact from a climate change perspective, as well as – Caroline points out – the less obvious impacts such as risks to human health and natural ecosystems, LCA emerges as a necessary design tool. “It provides the rigorous, scientific framework needed to take on that responsibility,” Caroline adds. “It allows us to quantify the environmental load of our choices and identify the products that genuinely contribute to creating cleaner, healthier and more resilient buildings.”

The four stages of LCA

To ensure consistency and rigour, an LCA follows four distinct phases, which Caroline breaks down into Goal and Scope, Inventory Analysis, Impact Assessment and Interpretation.

The first step – Goal and Scope – defines the purpose. “We consider what exactly we want to measure and what the boundaries of our study are,” Caroline explains. This could be a “cradle-to-gate” analysis, which covers the product from its inception until it leaves the factory, or a comprehensive “cradle-to-grave” assessment.

Then, the second step – Inventory Analysis – involves meticulously cataloguing all inputs, such as energy, water and raw materials, and outputs, including emissions and waste, at each stage of the product’s life. This raw data is then used to understand the environmental impacts during the third phase – Impact Assessment. “This is where we see how the inventory data contributes to specific issues like climate change, resource depletion or ecosystem toxicity,” says Caroline.

Interpretation, which is the final phase, involves analysing the results from the previous steps to draw conclusions and make recommendations. “This is the crucial part,” Caroline notes. “What does the data mean? It allows us to pinpoint the biggest areas of impact and provides a clear basis for comparing different products.”

Understanding the data: GWP and EPDs

Caroline explains that for industry professionals, the most direct way to access LCA data is through Environmental Product Declarations (EPDs) – standardised, third-party verified documents that transparently report a product’s environmental impact based on its holistic lifecycle.

Rich with data, these documents can be challenging to navigate. What to look for? Caroline points to the most critical indicator for carbon impact: the Global Warming Potential (GWP), which measures the effects of greenhouse gases on global warming. “The GWP is a measure of how much heat a greenhouse gas, like carbon dioxide and methane, traps in the atmosphere over a specific period – usually 20 years – relative to carbon dioxide (CO2),” Caroline says. “It’s expressed in kilograms of CO₂ equivalent (CO₂eq).”

“In an EPD, GWP is broken down by life cycle stage,” Caroline explains, listing A, which is the raw materials and manufacturing stage, B – use stage, C – end-of-life stage and D, which is the recovery stage. Caroline points to the EPD for Knauf Gypsum’s Sheetrock® One 10mm plasterboard to demonstrate the point. “Here, you can see the impact of the manufacturing stages A1-A5. To find the total GWP, or the environmental impact, of raw materials and manufacturing, you simply add these values. For Sheetrock® One, that’s 1.615 kg CO₂eq per square metre.”

Caroline notes that this figure can then be directly and reliably compared with other products. “The lower the number, the less environmental impact the product will have,” she says. “However, it’s really crucial to pay attention to the details, here – the number could be low due to carbon offsetting rather than direct effort from the company to lower their operational emissions.”

Cradle to…: LCA theory in practice

While EPDs make LCA data accessible, Caroline acknowledges a common challenge for designers – understanding the scope of the assessment. “The most common challenge faced by architects and designers is not knowing the product life cycle used behind the published data – in EPDs, for instance. One EPD might be based around ‘cradle-to-gate’, while another – ‘cradle-to-grave’. To help address that, the published document must clearly state the product life cycle model that is being used or the scope or boundaries.”

Listing the most common LCA models, Caroline explains that cradle-to-gate – which is very common for EPDs – assesses a product from raw material extraction to the factory gate, while cradle-to-grave covers the entire product life cycle, from raw material extraction, manufacturing, processing and transportation to use, retail and disposal. “And then there is cradle-to-cradle, Caroline adds. “A model focused on circularity, where end-of-life products are recycled or reused, closing the loop.” Plus, to simplify the assessment, the gate-to-gate model assesses only one value-added process in the product chain. “These assessments can later be linked together to complete a larger level LCA,” Caroline explains.

Credible, verifiable and demonstrably sustainable

“Our EPD for Sheetrock® One, for example, clearly defines its boundaries as cradle-to-gate with optional modules covering end-of-life and recovery,” Caroline explains. “This transparency is non-negotiable. It’s what allows specifiers to integrate LCA data into their workflows confidently and make decisions that are backed by credible, verifiable evidence.”

By embracing the clarity that data-packed LCA and EPDs provide, architects, designers and specifiers can take a leading role in creating measurable change. And while enduring design will never be achieved by numbers alone, actively leveraging this detailed information empowers the industry to create a built environment that is not only beautiful, functional and sustainable, but also demonstrably so.

Architecture & Design Team

Knauf

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