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All You Need to Know About: The differences in EPDs from different manufacturers

by Jennie Ward

In this ongoing series, Rob Firman of Polyfoam XPS looks at different aspects of flat roofing design and construction and helps to demystify them. This month he explains why looking for similarities and differences in EPD reporting is crucial.

Rob Firman of Polyfoam XPS.

Part of making sustainable construction product choices is comparing the environmental impact of different solutions by looking at environmental product declarations (EPDs). An EPD produced by one manufacturer could be quite different from an EPD produced by a different manufacturer for a similar type of product.

Looking for similarities and differences in EPD reporting is important so that an appropriate assessment can be made about whether a product is able to meet a project’s sustainability goals.

Is the EPD generic or specific?
For some products, you might only be able to obtain generic EPDs, where average data has been compiled based on information from a number of manufacturers. For example, a trade association might make available generic EPDs, having gathered data from its member companies.

That means you could ask for an EPD from two different manufacturers and be provided with the same document by both.
A generic EPD might broadly represent the environmental impact of your product specification. But if your project is unique in some way that won’t have been captured by average data, then the environmental impact reporting won’t be as accurate as it could be.

More specific data makes for better transparency about the environmental impact of projects. Preferable to a generic EPD is a manufacturer-specific EPD, which can apply to more than one product (within a particular category) produced by a single manufacturer. Better again is a product-specific EPD, which applies to a single product made by a single manufacturer.

Understanding functional equivalence
In EPD reporting, the environmental impact of the product is based on that product’s ‘unit size’. The unit size adopted for the EPD is known as the ‘functional equivalence’. When comparing EPDs from different sources, checking whether the functional equivalence is the same or different is important.

In EPDs for thermal insulation, for example, one material could use one cubic metre for the functional equivalence. Another could use one square metre of a specific product thickness.

A square metre of an insulation board that is 100mm thick is one-tenth of the volume of one cubic metre of insulation. The two insulation products could have a broadly similar environmental impact like-for-like, but the EPD would report substantially different figures.

Functional equivalence is chosen by manufacturers based on their production processes, so there is nothing to say that one choice is ‘correct’ and another is ‘wrong’. It is purely a case of watching out for the unit size of the material rather than taking the EPD reporting at face value.

What is the scope of life cycle reporting?
In last month’s Total Contractor we looked at life cycle assessment (LCA) and how EPDs report environmental impact across a series of stages and modules.

Typically, EPDs are a ‘cradle to gate’ type, a ‘cradle to grave’ type, or a ‘cradle to gate with options’ type. ‘Options’ means that relevant parts of the product’s end of life stage – module C – can be taken into account, alongside modules A1 to A3 (the production process).

This is useful for some products – insulation being a good example – where relatively minimal use stage (module B) impacts are incurred, but where the manufacturer wants to report a fuller scope than simply ‘cradle to gate’.

Again, this is not necessarily a judgement on what is correct and what isn’t. In an ideal world, all products would report across every single module to give a complete picture of environmental impact. As EPDs and their availability continue to mature then we will likely find that full and consistent level of reporting.

With regards to this discussion on ensuring fair comparisons are made, the important thing to remember is that the scope of reporting for similar products could be different. When making an assessment of whether a product is the right choice for a project, that difference should be borne in mind.


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