Comparing Environmental Product Declarations (EPDs) within One Click LCA is a powerful way to support life cycle assessment (LCA), procurement decisions, and sustainability reporting. However, even EPDs for seemingly similar products can present challenges when directly compared. This guide highlights the most common pitfalls users encounter in One Click LCA and helps you understand what to look for in an EPD document and how to properly compare different EPDs.

An environmental product declaration (EPD) is a document that transparently reports the environmental impact of a product or material throughout its lifecycle. EPDs support carbon emission reduction targets by making it possible to compare the impacts of different materials and products in order to select the most sustainable option for buildings or infrastructure.

A third-party verified EPD is usually valid for five years, and is generated according to the relevant standards. Construction EPDs are based on the ISO 14040/14044, ISO 14025, EN 15804 or ISO 21930 standards.

The environmental impacts are assessed according to specific Product Category Rules (PCRs), which ensure consistency and comparability across similar products. EPDs are designed to be transparent and do not include proprietary information, focusing instead on disclosing environmental data that is essential for stakeholders, including consumers, regulators, and industry professionals.

EPDs can differ based on their application and verification.

Third-party verified EPDs are the most widely recognized type of EPD, they are required by many regulations and certification schemes and accepted by almost all. As well as being third-party verified in compliance with ISO 14025, they are published by an EPD program operator and can be used for almost any purpose. A third-party verified EPD is valid for 5 years unless the parameters change.

Some EPD program operators offer Variant EPDs that are based on an already published third-party verified EPD. Variant EPDs must be similar to the third-party verified EPD they’re based on; they must be manufactured using a similar process, from similar raw materials, and for a similar function. This type is also in compliance with ISO 14025.

Project EPDs are created for a specific project or contract. They are non-published documents verified internally by designated qualified personnel or through a company’s established quality management processes, rather than being reviewed by external program operators or made publicly available. Project EPDs facilitate the scaling of EPD adoption without the expenses associated with third-party verification for each declaration. Although Project EPDs comply with ISO 14025, they are distinctly marked as “Internally Verified” to clarify their verification status. Some program operators assign shorter validity for Project EPDs.

Automatically generated EPDs for a large number of products which are generated by a system on-demand, meaning the individual documents themselves are not subject to direct verification, but the process or system generating them has been verified. The verification is done on the system that produces the EPDs, ensuring that it meets certain criteria. However, this means the final document itself is not necessarily individually checked or verified. The need for scalable EPD solutions, such as system verified EPDs, has arisen due to the growing demand for environmental documentation in the construction industry. However, system verified EPDs raise concerns around transparency since these automated systems don’t always provide the same level of scrutiny as traditional, manual verification processes. These documents are widely used in building LCAs for certain product categories, such as ready-mix concrete.

For an EPD to qualify as third-party verified, the verification process must clearly indicate that the final EPD document has been reviewed and approved by an independent verifier. System verified EPDs don’t always meet this criterion, which could be an issue for certain certifications or standards that require explicit third-party verification. To ensure your EPD is third-party verified make sure to always check that the verification statement clearly mentions that the final document has been viewed and verified by a verifier. In traditional third-party verified EPDs, a third-party verifier confirms that the life-cycle assessment (LCA) and the EPD document conform to standards (ISO 14025, EN 15804).

Always note the verification statement. In system verified EPDs, only the generation process or method will be noted as verified, as shown in the example below:

EPDs provide valuable insights about a product’s environmental performance at a glance. However, EPDs may vary in appearance depending on the Product Category Rules (PCRs) they follow and the program operator that publishes them.

An EPD covers the following information:

To effectively compare different EPDs, or to go through the most important information of an EPD, you should focus on these five key points:

Reference standards used for the EPD

The reference standards used for the EPD are the official guidelines and scientific methods followed to calculate and report the environmental impacts. These standards ensure that the EPD is produced using reliable, recognized methodologies, so the data is comparable across similar products and is accepted in the industry. Construction EPDs are based on the ISO 14040/14044, ISO 14025, EN 15804 (versions EN+A1 or EN+A2) and/or ISO 21930 standards. In the example EPD below, you can find this information under EPD Standards, Scope and Verification:

Period of validity

The period of validity refers to the time frame during which the EPD remains accurate and relevant. EPDs are based on data that can change over time due to shifts in manufacturing processes, energy sources, or supply chains. This period ensures that the environmental impact data provided is up-to-date and reliable for a specific duration, 5 years for third-party verified EPDs. This is to prevent outdated or misleading information from being used after significant changes to the product.After this period, the EPD should be reviewed or updated to reflect any changes. This example EPD below, has validity for 5 years:

Verification

This means an independent organization has reviewed the data and processes used in the EPD to confirm its accuracy. Third-party verification adds credibility to the EPD, showing that the environmental impacts, such as carbon emissions, are calculated properly and are based on reliable information. Some certification schemes require the use of third-party EPDs whereas some accept internally verified versions as well.

The environmental data summary

The environmental data summary provides key information about the product’s environmental impacts such as

Declared unit

You can find the the declared unit under product description. Declared unit is the reference point for measuring environmental impact. It's like saying "calories per serving" when describing food nutrition. For construction products, this might be measured in terms of weight (e.g., kilograms of concrete) or volume (e.g., cubic meters of a material). The declared unit standardizes the environmental data so that the impacts, such as emissions or energy use, are compared on the same basis across different products.

By checking these elements, you ensure the EPD is current and that you're examining the intended product. This approach helps you understand the characteristics for comparison, including type, impact, and unit.

Manufacturers, architects, and engineers often need to compare EPDs when selecting suppliers or choosing products with the lowest environmental impact for their projects. To make a fair and accurate comparison, it's essential to focus on couple key points which can can cause some pitfalls.

1. Varying Declared Units

Issue: EPDs may use different declared units (e.g., per m2, per kg, per piece), which lead to incorrect comparisons.

Example: A floor tile EPD declared per m2 vs. a carpet tile EPD declared per piece.

Solution in One Click LCA: Convert declared units to a common functional unit using the tool's built-in unit conversion features. Always verify the conversion aligns with the functional requirements of your project.

2. Functional unit declared in EPD vs. Functional relevance

Issue: EPDs present impacts per declared unit but real-world use may require functional comparisons based on performance.

Example: Comparing insulation materials per kg instead of per unit of thermal resistance delivered.

Solution in One Click LCA: Define functional units that reflect actual performance requirements (e.g., thermal resistance, load capacity, whole structure of a wall). Add the materials and adjust quantities accordingly. Compare the life cycle impacts on the LCA tools on Construction material page to include full life cycle impacts to your comparison. If you only want to compare manufacturing emissions, Material Compass is the easiest tool to do the comparison.

3. Scope of the EPDs

EPDs might report different life cycle stages and impact categories based on the standards they follow:

Issue: EPDs may follow different LCA standards or versions, affecting life cycle stages reported.

Example: One EPD is calculated using EN 15804+A1, while another follows EN 15804+A2.

Solution in One Click LCA: Pay close attention to the EPD version filters available within the database or use the generic assumptions to cover missing life cycle stages (e.g. C module scenarios based on the market).

4. Impact Assessment Methods (LCIA) vary affecting the environmental impacts reported in the EPD

The environmental impact categories vary depending on the reference standard the EPD is aligned with. Common categories include:

More about impact categories here & here.

Issue: EPDs may follow different LCA standards or versions, affecting impact category calculations.

Example: One EPD is calculated using EN 15804+A1, while another follows EN 15804+A2.

Solution in One Click LCA: Pay close attention to the EPD version filters available within the database. Avoid mixing A1 and A2 EPDs directly. In case you compare EPDs following different standards, ensure that you compare comparable impact categories with similar units and check the background assumptions (for example for bio-based products on how biogenic content has been declared) to avoid inconsistencies.

5. Differences in Product Composition or Performance

Some products might have different expected lifespans and performance expectations. Comparing them on a per-year basis (e.g., GWP over 50 years of service) can provide a clearer picture, especially if one product lasts significantly longer.

Issue: Products may serve the same function but differ significantly in composition, durability, or performance.

Example: A composite wood panel vs. a solid wood panel with different lifespans.

Solution in One Click LCA: Utilize the service life inputs to account for differences in product lifespan, replacement cycles to compare products over the whole life cycle.

System boundaries

Understand what is included in each EPD. Some may cover additional or fewer processes, such as transportation, energy use in operation, or end-of-life disposal. The system boundary should be consistent to ensure all aspects of the product’s lifecycle are accounted for similarly.

In One Click LCA's building and infrastructure tools, it is possible to use some typical regional scenarios to cover missing life cycle impacts or to make a fair comparison according to specific standards.

Data quality and sources for the EPD

The EPDs can be made with different background data (life cycle inventory). Primary data (from actual manufacturing processes) is generally more reliable than secondary data (from databases or literature). Products with well-documented, high-quality data are easier to compare accurately. You can find this information in the 'LCA background information' section.

Geographical and temporal differences

Geography can influence the environmental impact of a product (e.g., energy mix in manufacturing locations or transportation distances). Similarly, temporal differences (the year the data was collected) matter, as technologies and regulations change over time. Where necessary, apply regional loclisation factors or prioritize EPDs that match your project location and time frame.

Material composition and recyclability

Consider the materials used and their potential for recycling or reuse. A product with a high environmental impact during manufacturing might offset this by being highly recyclable or having a long lifespan.