EPDs Comparability: When and how EPDs can be compared

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Can Environmental Product Declarations be compared?

Can EPDs be used to choose construction products?

The short answer: All other things being equal, yes. Otherwise only via building level LCA.

The long answer? Well, now that you’re asking…

Environmental Product Declarations provide the necessary product carbon performance data

To develop a low-carbon economy, it’s essential that buyers can evaluate and choose low-carbon products, services, and assets. This, in turn, requires reliable environmental impact information. This information can be found in Environmental Product Declarations (EPDs).

EPDs are relatively complex technical documents. Good news is, if you are trying to reduce carbon, you do not have to go through all of it, as what you’re looking for is called Global Warming Potential (GWP). Usually, this is expressed as a scientific number, so if your EPD says GWP of a kg of product is 2,5E-2, that means it’s 0,025 kg CO2e.

So pick the product with the product with the lowest GWP and run with it, right? Not so fast. Most have heard the story of three little piggies and their houses – where two piggies chose materials inadequate for their environmental conditions (the story does not tell if EPDs were involved).

All other things being equal, choose the product with lower manufacturing impacts in its EPD

Other things being equal, choosing a product with lower carbon emissions for a project is a good choice. However, other things are not always equal. I saw recently a comparison of manufacturing impacts of paper to steel. Do you see yourself reading your news engraved on a steel plate with your morning coffee? The first thing is to ensure all the compared alternatives can fulfill the intended purpose of use.
If a product is compared just for manufacturing impacts to another one, this can lead to several different sub-optimization traps, including:

  • the alternative requires more replacements during building life-cycle
  • the alternative generates additional demand for other products, for example, if the floor slabs become thicker, external walls become thicker, too (even if slabs would save CO2e in themselves)
  • the alternative has higher life-cycle impacts due to maintenance, end of life processing, etc
  • the alternative or design using it changes operational energy balances, e.g. via daylighting, conductive heat loss, thermal capacity or other parameters

This is why the direct comparison of EPDs as such (and not via LCA) should be done only between very similar products that do not differ in the above respects.

If all other things are not equal, compare the products at the building level using LCA methodology

If you consider for example options for a façade, most likely the options also differ in terms of operational energy performance. Also, in this case, the EPD is an essential tool for the comparison, as it provides the manufacturing impacts which is one part of the whole-building level impacts.

In these cases, a comparison is possible via building LCA. If the options vary in terms of operational energy use, in terms of envelope shape or layer thicknesses, all that is bread and butter of types of analyses LCA can provide an answer for. LCA will provide the whole life-cycle impacts cradle to grave. This means comparing the product environmental impacts for the lifetime of the building into which they are planned to be installed, in the conditions that the building requires.

All EPDs compared need to fulfill the minimum quality requirements.

Are all EPDs equally good?

Well, not really, but it’s getting a lot better. While all EPDs are not equally good, with competence and some diligence, they most certainly can be used for comparisons.

An Environmental Product Declaration (EPD) is a tool for reporting product environmental performance, including carbon and other LCA-relevant information. EPD is always third-party verified and follows a minimum set of ISO standards as well as specific Product Category Rules. European and many international EPDs also comply with EN 15804, and some with the more recent ISO 21930 standard. And in fact, the ISO 21930 and EN 15804 are in themselves “core PCRs”, so they provide the core rules of assessment to any PCR that complies with those standards. This means that the PCR can’t deviate from the core rules. And this means these EPDs can indeed be used in a comparison.

Sounds like it would be better if someone checked all the EPDs and put them in line?

As you may have guessed, this is a topic we’ve been working with at One Click LCA. We have checked pretty much every construction EPD there is, and integrated into our platform the vast majority of them. Excepting a few programs whose quality is unsuitable, we cover all EPD programs globally.

In the One Click LCA database, almost all products are classed to by carbon performance relative to all products in the product type they represent (for example, gypsum board). The database contains over 100 different product types to ensure the benchmarks are meaningful, and over 10 000 EPDs and generic LCA profiles. We’ve excluded from benchmarking products with unusual properties, and have marked legitimate data whose values simply are outliers e.g. due to very high recycled content.

We’ve also always made sure that biogenic carbon handling is done in a uniform fashion. We have two types of databases, ‘regulated’ and ‘general’ ones. The former group consists of data that must be used as is due to requirements of local certification, such as IMPACT methodology for BREEAM UK, irrespective of whether biogenic CO2e was deduced from manufacturing impacts. Databases in this category include INIES, IMPACT, NMD, and OKOBAU.DAT. What we had done so far is to simply not offer such datapoints with differing biogenic carbon handling to generic use at all.

The essential improvement we’re introducing now is showing biogenic carbon storage separately for all products, even if the underlying EPD did not report it separately. In those cases, our database team has analyzed the EPDs carefully and calculated the biogenic carbon storage for its composition. And for ‘regulated’ databases we have created mirror copies of the datasets with this aspect addressed for our general database (except of course when the database terms do not allow this).

In short, what this means is that our database engineering team has put in half a decade of work to sort, check and organize every EPD in the world for you. We also continue doing this for all new data and are constantly updating the database with new data. You can compare them with confidence.

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