Product Category Rules (PCR) :
as described for building products in ISO 21930

• Product Category Rules are a set of rules, requirements and guidelines for developing Environmental Product Declarations (EPD) for one or more product categories.

  • A Product Category is a group of products that can fulfill equivalent functions - for example, 'floor finishes', 'concrete blocks' or 'insulation'.

• PCR for building products, as set out in ISO 21930, are a particular refining of those as set out in ISO 14025.

• Product Category Rules are a natural step in delivering the kind of information that is standardised through a group of similar-in-function products or materials. PCR are particularly useful where the environmental impacts of products within a category group are to be compared - perhaps as part of a product specification process. Rules provide a level playing field, enabling apples to be compared with apples, or, more appropriately, insulation to be compared with insulation or carpet with carpet.

• Many PCR exist because each category group is associated with a PCR that concentrates on the kind of environmental impacts that are unique to that group.

• Product Category Rules are of course an integral part of generating an Environmental Product Declaration and are introduced in ISO 14025. Set out in that standard is the basic procedures and requirements for establishing a PCR for any product category.
product category rules as part of an epd
• Many PCR have already been written for specific markets such as Europe or North America. There are a number of repositories where rules are hosted such as the international GEDnet or the American Center for Life Cycle Assessment .  


The building product as part of determining a building's overall impact

The PCR as set out in ISO 21930 closely matches that of ISO 14025. Where it differs is as through the recognition of a product / material as a functioning component of a building. The goal of this ISO neighbourhood of standards is to be able to assess the overall environmental impact of a building which it does by aggregating all the environmental impacts for each individual component / functioning unit of the building. The total impact is determined as the sum of these unit parts.


The requirements of a PCR for building products

The PCR should identify the goal and the scope of the information for the product category, for example a PCR already written for insulation declares, in a straightforward manner, that the rules should 'give guidelines for carrying out EPD for insulation materials' and users will include '… manufacturers of insulation materials and other interested parties.'

According to ISO 21930, the PCR shall also ' … determine the life-cycle stages for inclusion, the parameters to be covered and the way in which the parameters shall be collated and reported.'



The requirements in detail:

(a) A definition and description of the PCR.

- For example a PCR for 'Floor coverings' provides an inventory of which floor coverings it includes, such as 'textile floor coverings, laminate floor coverings and resilient floor coverings manufactured from plastics, linoleum, cork etc.

- It also informs that an EPD developed on the back of the PCR can be for individual products, product groups or 'average' products.

(b) The goal and scope for the production of Life Cycle Assessments (LCA) :

- The functional unit: which is defined for building products by ISO 21930 as related to the building or part of a building and its performance. Essentially, then it refers to the products function as part of the building and includes all data covering from cradle to grave. For example, the PCR for 'Floor coverings' states that a functional unit as possibly being '1m2 of floor covering for a specified application and use area according to EN 685 and reference service life.'


- The declared unit: for declarations not covering the complete life cycle, for example concentrating on the manufacturing stage and leaving out the product's use within the building or its final disposal (usually in the case where the function cannot be defined, or there are many possible functions), the functional unit is considered to be a 'declared unit'. Using our floor covering example, the declared unit, which covers only the production stage, would be defined as '1m2 of floor covering with specified construction/composition parameters.'

- The system boundary: products and materials are, by nature, integrated in other systems and processes. To address the issue of seemingly endless data aggregation, limits need to be set. The system boundary places a 'fence' around areas of the LCA data that need to be included to make sense of the product's main environmental impacts and excludes other areas that might include secondary materials or by-products or perhaps where it bumps into another system. ISO 21930 goes into further detail of how the boundary conditions should be treated.

- Description of data: sets out the kind of data that is to be included. It looks at where the data comes from, how much there is of it and its quality. The standard emphasises that product specific information is much preferred over 'average' or 'generic' data, use of which should be justified.

- Criteria for the inclusion of inputs and outputs: looks at what's in and what's out from of the data collection. This attempts to simplify, and therefore make comprehensible, what could be an unnecessarily complicated data set. Commonly, inputs and outputs that have a negligible effect on the impact of the product can be excluded, although all hazardous and toxic materials and substances must be included irrespective of the size of their impact.

- Data quality requirements including coverage, precision, completeness, representativeness, consistency, reproducibility, sources and uncertainty

- Units: are for inputs and outputs where energy is measured in megajoules or kilowatt hours and mass is measured in tonnes, kilograms or grams.

(c) Inventory analysis: carried out according to ISO 14044 sets out the requirements for data collection and modeling of the product system, as well as description and verification of data. ISO 21930 states that the 'life-cycle inventory process…' is of 'special importance'.

(d) Impact category selection and calculation rules: ISO 21930 sets out a number of environmental impact categories (eg climate change) that must be included as part of the EPD.

(e) Predetermined parameters for reporting of LCA data: sets out how data will be presented from life cycle assessments.

(f) Requirements for the provision of additional information: outlines the kind of additional information related to environmental issues. Reference is made to a range of issues that are listed in ISO 14025 such as data on product performance or environmental and human toxicity.

(g) Materials and substances for declaration: this key clause sets out the requirement for the listing of materials and substances, including those that might be toxic to humans and/or the environment.

(h) Instructions for producing the data required to develop the EPD

(i) Instructions on the content and format of the type III environmental declaration: sets out how the EPD will be composed.

(j) Information on which stages are not considered: where some stages of the LCA have been omitted, they should be listed.

(k) Period of validity