A Product Category Rule (PCR) is a consensus-based document that prescribes the set of rules and methods for environmental life cycle assessments (LCAs) and the resultant Environmental Product Declarations (EPDs) that apply to a product or category of products.

The LCA requirements in the PCR are developed in conformance with the ISO 14000 family of standards addressing environmental management including ISO 14040 "Environmental management – Life cycle assessment – Principles and framework" and ISO 14044 "Environmental management – Life Cycle assessment – Requirements and guidelines." An additional ISO standard, ISO 21930 "Sustainability in buildings and civil engineering works - Core rules for environmental product declarations of construction products and services," establishes the basic rules for EPDs consistent between all types of products and services in the construction marketplace.

While not contradicting the core rules in ISO 21930, the standard allows product sectors to expand the core rules in the standard applicable to the products in that particular sector. These expanded rules are known as sub-sector product category rules or simply "Product Category Rules."

The PCR is developed by a committee of experts under the guidance of a moderator fully conversant with the ISO requirements, the application of LCAs, and the product sector developing the PCR. The moderator assembles a committee of LCA and industry experts to develop the language in PCR addressing content required under ISO 21930. That content includes the general aspects of the PCR including its scope, life cycle stages, rules for the conducting of the life cycle assessment upon which the EPD will be based, required and optional modules and types of EPDs allowed, and the required content of the EPD.

Typically, the moderator’s organization will have published a generic version of the PCR requirements based on ISO 21930. This generic version is known as "Part A" and will form the basis of the committee’s discussions in the development of the product sector specific EPD referred to as "Part B." Part B can simply reference Part A, modify the requirements of Part A or extend the requirements of Part A. The committee does not edit Part A, but includes any changes to its requirements in Part B.

The committee creates a consensus draft of the PCR which is then released for public comment. The committee reviews the public comments and makes any changes felt to be necessary in Part B. If those changes are substantive a second public comment period may occur.

Following agreement on a final draft, the draft is sent to a panel of independent experts for final review as to the draft PCRs conformance to ISO 21930 requirements and appropriateness for the PCR's product sector. Following any changes resulting from the expert panel review, the PCR is issued for use. The PCR is valid for a period of 5 years from the date of its issuance, and all EPDs published by industries or product manufacturers covered by the scope of the PCRare required to comply with it.

Structural steel products are subject to the "Smart EPD® Part B Product Category Rules for Designated Steel Construction Products, Standard 1000-008, version 3" published on April 3, 2025 available in the Smart EPD® PCR Library. The PCR was developed by a committee of 28 industry experts representing a total of 24 government agencies, trade associations, and private firms. Moderation and the Part A PCR was provided by Smart EPD.

The PCR is applicable to all steel construction products used and/or sold in North America including mill level products, products primarily manufactured from mill level products, as well as the fabrication process based on specific project requirements. The distinction being made in the PCR is that unlike mills and manufacturers who create a new product, fabrication does not result in a product but merely modifies an existing product to meet the requirements of a specific project. The PCR does not apply to steel products that have an existing PCR specifically addressing them such as metal ceiling and wall panels, insulated metal panels, metal cladding, pipe, and conduit. The PCR also does apply to products applied to steel products after fabrication or installation such as galvanizing, painting, epoxy-coating, or fire protection materials.

The PCR requires that the results reported in an EPD be based on a specific declared unit. For steel construction products that declared unit is one metric ton of steel and expressed using metric units such as kilograms of CO2e per metric ton of steel.

Following ISO 21930, environmental impacts are organized into modules that are represented in the following chart:

Product stage modules, sometimes referred to as Cradle-to-gate modules, A1 to A3, are required in all EPDs while all other modules may optionally be reported.

All EPDs must include a system boundary diagram illustrating the processes used in the production or manufacture of the product and the boundaries between the reported modules. Processes not relevant to the product and modules not reported are to be grayed out.

The PCR is organized around three product and process options:

• Option 1: mill products – products produced at steel mills using iron ore, steel scrap or semi-finished steel (billets, blooms, slabs), Common examples include unfabricated rebar, unfabricated hot-rolled sections, unfabricated plate, coil, rods, wire, light-sections, merchant bar, and sheet piling.
• Option 2: manufactured products – a mill product or products transformed into a new product through a manufacturing process. Common examples include hollow structural sections, open-web steel joists, steel deck, and PC strand.
• Option 3: Fabrication – is the process of cutting, drilling, and welding mill or manufactured products to satisfy the requirements of project-specific design documents.

The content of modules A1, A2, and A3 vary by the product and process options.

For Option 1 (Mill Product):

• A1 includes extraction and processing feedstock materials
• A2 includes transportation of the feedstock to mill facility
• A3 includes mill operations

For Option 2 (Manufactured Product):

• A1 includes the sum of A1, A2, and A3 values for the quantity of mill products used in the manufacturing process, including the amount of steel that becomes manufacturing scrap
• A2 includes the transportation of mill products to the manufacturer’s location
• A3 includes manufacturing operations

For Option 3 (Fabrication), two alternatives exist, the first being the fabrication process (3A) itself:

• A1 is the overage rate of material required to produce one metric ton of fabricated steel. The overage rate is expressed as a percentage based on the industry average. The current industry average overage rate for structural steel products as determined by a survey conducted of AISC member fabricators is 7.71%, meaning that 1.0771 metric tons of steel are required on average to result in 1 metric ton of steel being shipped to a project site.
• A2 includes the transportation of the product from the mill or manufacturer's facility to the fabricator.
• A3 includes fabrication operations.

Under version 3 of the PCR, EPDs for mill and manufactured products are not to include fabrication impacts in their primary tables in the results section of the EPD. Fabrication impacts may be combined with mill or manufactured impacts in a table in the "Additional Environmental Information" section of the EPD. In that case, A1 would include the sum of A1, A2, and A3 for the mill or manufactured product increased by the overage rate, A2 the industry-average transportation from the mill to fabricator and A3 the industry-average fabrication operations. The values for the overage rate, A2, and A3 must be the industry-average values determined by AISC and cannot be changed by the mill or manufacturer.

A second alternative is applicable only in the rare case when it is required to document the impacts associated with a specific project (3B). The PCR should be consulted regarding the specific requirements of that scenario.

Optional modules, if reported, are to be reported using the following guidelines:

• A4 – for unfabricated products A4 shall include the transportation from the mill or manufacturer to the project site. For fabricated products A4 shall include only the transportation from the fabricator to the project site as the transportation from the mill or manufacturer has already been reported in the fabrication process A2.
• A5 – shall include impacts associated with the on-site preparation of the product for installation, the installation/erection of the product, and any waste generated by the erection process.
• B1 to B7 – shall be reported as 0 unless the product has a reference service life of less than 75 years or the service life of the structure. Module B impacts related to maintenance and repair of coating systems are to be reported in the EPD for those products, not the underlying steel product.
• C1 to C4 – should be based on primary data or industry-average values related to the deconstruction/demolition of the structure (C1), transportation of the waste to a processing facility (C2), processing of the waste (C3), and disposal (C4).
• D – is a speculative value based on the anticipation of the future reuse or recycling of the steel product that is based on the net difference between the recycled content of the product and the recovery rate of the product. While informational it should not be combined with any other modules in reporting the overall environmental impacts associated with the product.

The PCR allows for several different types of EPDs with increasing levels of specificity:

• Industry-average EPDs reporting environmental impacts for the same product from multiple mill producers or manufacturers. The results are based on weighted averages of individual production sites. A minimum statistically valid representation of the overall production of the product is required and is to be documented in the EPD.
• Product-specific producer-specific reporting the environmental impacts for the same product from multiple production sites owned by the same producer.
• Product-specific facility-specific reporting the environmental impacts for a single product from a single, identified production site.

In addition to these general requirements, version 3 of "Part B Product Category Rules for Designated Steel Construction Products" addresses several topics specific to the production, manufacture, and fabrication of steel construction products. These include:

• Slag produced during mill operations is considered a co-product, not a waste product; as it is sold, not disposed. Therefore, the environmental impacts associated with the slag are not included in those of the mill product but passed downstream to the consumer of the mill slag.
• Electricity purchased from the grid shall not be accounted for using national or continental (East, West, or Texas) grid mixes.
• Facilities using on-site renewable electricity with no Energy Attribute Certificates (EACs) having been sold to a third party may take credit for that electricity generation in the primary results table of the EPD.
• Facilities purchasing renewable energy through the use of EACs may take credit for those purchases in the primary results table of the EPD as long as the facility owner attests that the certificates will not be sold or transferred.
• It is the stated intent of the PCR that the latest version of the ACLCA "Guidance for Quantifying Renewable Electricity Instruments in Environmental Product Declarations" will be followed.
• To improve transparency and data quality, an evaluation in the EPD is required addressing temporal, geographic, technical representativeness and completeness of data.

This is but a sampling of the detailed information in the latest version of the PCR and is only intended to give a sense of the structure and requirements that the PCR establishes for the EPDs produced under it. The text here should not be relied upon to create or interpret an EPD. The PCR itself is the only source of definitive information regarding the EPDs being published within its scope.

The reader is strongly encouraged to dig deeper by reading not only Part B PCR for Designated Steel Construction Products, 1000-008, v3.0 but also Smart EPD®'s Part A Product Category Rules for Building and Construction Products and Services, both of which can be found in the Smart EPD® PCR Library and ISO 21930:2017.