Authored by Vertima, Greenbuilding and Materials Experts: Is it possible to compare the Environmental Product Declarations (EPDs) of different suppliers with the goal of selecting the one with the least environmental impact?

Only in rare circumstances is this possible. However, the demand from building owners and architects to realize this comparison is on the rise. In order to be compared, the products detailing EPDs1   should, inter alia, be 2,3 :

  • functionally equivalent;
  • based on the same functional unit(FU);
  • based on the same product category rules version;
  • analyzed according to the same life cycle impact method version, (ex:  TRACI v2.1 for North America);
  • modeled identically (used data, system boundaries)

Let’s see what functional equivalence and functional unit mean. The EPD’s results based on Life Cycle Assessment (LCA) are quantitative and represent the product’s potential environmental impacts on:

  1. its entire life cycle, namely from raw materials extraction through manufacturing, transportation and use, until end of life (from cradle-to-grave); or,
  2. a part of its life cycle, in other words, the majority of the time, from its extraction to its manufacture (from cradle-to-gate).

In the case of a cradle-to-grave LCA, the results are presented in relation to a functional unit (FU), which is a quantified performance of the product system. This functional unit is determined by the product function. A functional unit for an insulating glass could be: 1 m2 of window having a thermal insulation coefficient of 1.2W / m2K valid for 20 years.

In the case of a cradle-to-gate LCA, the results are presented in relation to a declared unit (DU), which is usually a mass, volume or surface unit (e.g. 1m2 of 6mm thick glass). Functional equivalence is no longer taken into account, as are several stages of the life cycle: transport to the user, product installation, use, and end of life. If, for example, your mass-equivalent product has a greater thermal insulation coefficient than your competitor and is recycled at the end of its life, while the competitor’s product is sent to the landfill site, the cradle-to-gate EPD’s results do not consider this difference. As a result, you will always find in a cradle-to-gate EPD a statement that the EPD itself is not comparable. Succinctly, we cannot compare apples to oranges!

Another important element is data. EPD results are derived from modeling that requires volumes of data to represent the processes included in the product life cycle. To model the same process, different data can be selected and thus create discrepancy in the results without the systems being different.
Finally, several other criteria must be respected, such as the same product category rules, the same life cycle impact method, and the same system boundaries in order to be able to compare EPDs.

In a nutshell, it is very rare that all conditions are met for EPDs from different manufacturers to be compared. On the other hand, the new LEED v4.14 provides for a new credit in the case where the manufacturer’s product demonstrates a reduction in impacts related to the climate change impact category. Therefore, the EPD are a useful tool to be used to demonstrate the environmental profile improvement of a company’s product over time.



1A Construction Product EPD is the simplified communication of the Life Cycle Assessment (LCA) results done in accordance with ISO 14025, 14040, 14044. 21930 and following the Product Category Rules (PCR).
2ISO 21930:2017  Sustainability in buildings and civil engineering works – core rules for environmental product declarations of construction products and services
3ISO 14025 :2006 Environmental labels and declarations — Type III environmental declarations — Principles and procedures


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