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Life Cycle Assessment (LCA) 101

What it is, why it matters, and how to read one

8 min readUpdated April 2026Sign in to save

What is a Life Cycle Assessment?

A Life Cycle Assessment (LCA) is a systematic method for measuring the environmental impacts of a product, process, or service across its entire life - from raw material extraction, through manufacturing and use, to end-of-life disposal or recycling.

In construction, LCA is used to quantify the environmental footprint of building materials and whole buildings. It answers the question: what is the total environmental cost of this product, not just at the point of manufacture, but across its entire existence?

LCA is governed by international standards ISO 14040 and ISO 14044, which define the principles and framework. For construction products specifically, the European standard EN 15804 sets out the rules for how LCAs should be conducted and reported in Environmental Product Declarations (EPDs).

Note. LCA is the methodology. An EPD is the document that communicates LCA results for a specific product. Think of LCA as the science and EPD as the report card.

Why LCA matters for construction

Construction accounts for roughly 40% of global carbon emissions, and material choices are a major driver. Without LCA, claims about sustainability are just opinions. With LCA, they become measurable, comparable, and verifiable.

LCA matters for three practical reasons. First, it prevents burden-shifting - solving one environmental problem by creating another. A material might have low carbon emissions but high water pollution, and LCA captures both. Second, it enables genuine comparison between alternatives on a like-for-like basis.

Third, it is increasingly required by regulations, planning authorities, and sustainability rating schemes like BREEAM.

As a specifier or buyer, understanding LCA basics means you can read EPDs critically, ask suppliers the right questions, and make material choices backed by evidence rather than marketing.

The lifecycle stages (A1 to D)

EN 15804 divides a product's lifecycle into standardised stages, each identified by a letter-number code. Understanding these stages is essential for reading any EPD or LCA report in construction.

Lifecycle stages - A1 to D

  1. 1

    A1–A3

    Product stage

  2. 2

    A4–A5

    Construction

  3. 3

    B1–B7

    Use stage

  4. 4

    C1–C4

    End of life

  5. 5

    D

    Beyond lifecycle

Tip. When comparing products, always check which lifecycle stages are included. Comparing A1-A3 data from one product with A1-A5 data from another gives a misleading result. Like-for-like means same stages, same functional unit, same service life assumptions.

What LCA actually measures

LCA does not just measure carbon. It quantifies multiple environmental impact categories, each capturing a different type of harm to the environment. This is one of LCA's greatest strengths - it gives you a rounded picture rather than a single number. The most commonly reported categories in construction EPDs are explained below.

Think of these categories like a health check-up. Carbon (GWP) is like blood pressure - important and widely tracked - but it does not tell you everything about a product's environmental health. A material might have low carbon emissions but cause significant water pollution or deplete scarce mineral resources. Reviewing multiple categories prevents you from solving one problem while unknowingly creating another.

TopicDetail
GWP (Global Warming Potential)measured in kg CO2 equivalent. This is the embodied carbon figure and the one most people focus on. It captures all greenhouse gas emissions (not just CO2 - also methane, nitrous oxide, and others) weighted by how much warming each gas causes relative to CO2. For example, 1 kg of methane is counted as approximately 28 kg CO2e because it traps 28 times more heat. When you see a product's 'carbon footprint', this is the number being reported.
AP (Acidification Potential)measured in kg SO2 equivalent. This measures emissions that cause acid rain and soil acidification - primarily sulphur dioxide (from burning fossil fuels) and nitrogen oxides (from high-temperature combustion). Acid rain damages ecosystems, corrodes buildings, and degrades soil quality. Products manufactured using coal or high-sulphur fuels tend to score higher. In practical terms, a brick kiln burning pet coke will have a higher AP than one burning natural gas.
EP (Eutrophication Potential)measured in kg PO4 equivalent. This measures nutrient pollution - excess nitrogen and phosphorus released into waterways and soil. These nutrients cause algal blooms that starve rivers and lakes of oxygen, killing fish and degrading water quality. Manufacturing processes that discharge wastewater, and agricultural feedstocks (like hemp or straw) that require fertiliser, can contribute to higher EP scores.
ODP (Ozone Depletion Potential)measured in kg CFC-11 equivalent. This measures emissions that damage the stratospheric ozone layer, which protects life on Earth from harmful ultraviolet radiation. For most construction products, this figure is very small. The exceptions are some older insulation blowing agents and certain refrigerants used in building services. Modern alternatives have largely eliminated this issue, but it remains a reported category.
POCP (Photochemical Ozone Creation Potential)measured in kg C2H4 (ethylene) equivalent. This measures emissions that contribute to ground-level ozone and smog - the harmful ozone at street level, not the protective ozone in the stratosphere. Volatile organic compounds (VOCs) and nitrogen oxides react in sunlight to form smog. Products manufactured using solvents or those that off-gas VOCs during use can have elevated POCP scores.
ADP (Abiotic Depletion Potential)reported in two parts. ADP-elements (kg Sb equivalent) measures the consumption of scarce mineral and metal resources relative to known global reserves - products containing copper, zinc, or rare earth elements score higher. ADP-fossil fuels (MJ) measures total fossil energy consumed across the lifecycle. Together, they tell you how much the product draws down non-renewable resources that cannot be replaced on human timescales.

Watch out. A product with the lowest GWP is not automatically the most sustainable overall. Always review multiple impact categories. A material might score well on carbon but poorly on water pollution or resource depletion. The 'best' product depends on which environmental impacts matter most in your project's context - a project near a sensitive waterway should weight EP more heavily, while one in an urban area might prioritise POCP.

The functional unit - why it matters

Every LCA is calculated per 'functional unit' - a defined quantity of the product that performs a specific function over a specific time period. This is the single most important concept for making fair comparisons.

For insulation, the functional unit might be: 1 m2 of insulation providing a thermal resistance of 1 m2K/W over a 60-year reference service life. This means you are comparing the amount of each material needed to do the same job for the same duration.

Without a common functional unit, comparisons are meaningless. Comparing 1 kg of timber with 1 kg of steel tells you nothing useful - they perform different functions and you use different quantities. Comparing the structural frame of a building using timber versus steel, designed to the same performance specification, tells you a great deal.

When reading EPDs, always check the declared or functional unit. If two products declare different units, you will need to convert before comparing.

How to read LCA results critically

LCA is a powerful tool, but it is not immune to manipulation or honest misunderstanding. Keep these principles in mind when reviewing LCA data.

TopicDetail
Check the scopewhich lifecycle stages are included? A1-A3 only, or cradle to grave? Partial LCAs can paint a very different picture from complete ones.
Check the data sourceis it product-specific data from the actual manufacturer, or generic industry-average data? Product-specific is more reliable and more relevant.
Check the functional unitare you comparing like with like? Same function, same performance level, same service life?
Check the programme operatorwho verified the EPD? Reputable programme operators (EPD International, BRE, IBU, INIES) have rigorous verification processes.
Check the publication dateLCA data has a shelf life. Manufacturing processes change, energy grids decarbonise, and supply chains shift. Data older than five years should be treated with caution.
Look beyond GWPcarbon gets the headlines, but other impact categories may be just as relevant for your project and its environmental context.

LCA in practice on Matera

On Matera, suppliers can upload EPD data for their products. When you see carbon figures, certifications, or environmental data on a product listing, LCA is the methodology behind those numbers.

Use the carbon comparison features to evaluate materials side by side, and always check whether the data is EPD-verified or self-declared. Verified data, backed by a published EPD from a recognised programme operator, is significantly more reliable than manufacturer claims alone.

Tip. Start with the guides on EPDs and embodied carbon if you want to go deeper. LCA is the foundation - EPDs and carbon data are where you will encounter it in day-to-day specification work.

Browse the libraryEPD Explained