How Environmental Product Declarations (EPDs) support UKNZCBS conformity: A guide for UK specifiers

What does the UKNZCBS standard require from your data?

UKNZCBS verification requires whole life carbon assessment aligned with the RICS Whole Life Carbon Assessment (WLCA) second edition methodology. That methodology establishes a clear data hierarchy. Manufacturer-specific data, in the form of third-party verified Environmental Product Declarations (EPDs), sits at the top. Industry average EPDs come next, and generic database values are the fallback.

What is an Environmental Product Declaration (EPD)?

An Environmental Product Declaration (EPD) is a standardised document, produced by or on behalf of a manufacturer, that quantifies the environmental impact of a construction product across its life cycle. EPDs for construction products follow EN 15804, the European standard that sets consistent Product Category Rules (PCR) across all product types, ensuring that impact data from different manufacturers can be compared on a like-for-like basis. An independent programme operator verifies that the data meets those rules before publication.

The life cycle of a product is divided into stages. For upfront carbon assessment in the UKNZCBS, the relevant life cycle stages are A1 to A5: raw material extraction and processing (A1–A3), transport to site (A4), and construction and installation (A5). A manufacturer-specific EPD provides verified A1–A3 data; the project team calculates A4 and A5 from site logistics and construction records.

The practical gap: When EPDs are absent

When a specified product lacks an EPD, the assessor uses generic database values. Those values are typically conservative, derived from older or averaged production data, and tend to overestimate the impact of a specific manufacturer's product. The UKNZCBS aligns with the RICS WLCA v2 methodology to calculate impacts. This methodology requires data quality scoring for the highest-impact materials in an assessment. Consistently low data quality scores increase uncertainty in the model and increase the likelihood of a project exceeding the upfront carbon limit, even on a well-designed scheme.

This creates a procurement risk. A product substituted during value engineering, or a specification change made on site without a corresponding EPD, can shift a project's carbon position after the design model was prepared. Because UKNZCBS verification is against as-built data, that shift will be visible to the verifier.

EPDs as a specification and procurement tool

This is where the practical implication lands for specifiers. Requiring EPDs at specification stage, and maintaining that requirement through procurement and any substitution process, is not administrative overhead. It is the mechanism that keeps design-stage carbon modelling aligned with what is actually built.

AECOM's approach on the net zero logistics project presented at the Carbon Experts Summit London is instructive: the team built a centralised carbon spreadsheet listing every material specification, with an assigned carbon value and a defined limit per material. That granularity depended on verified product-level data being available at the point of specification. Without it, the spreadsheet becomes a record of assumptions rather than commitments.

What specifiers should do to align with UKNZCBS?

Third-party verification with Bureau Veritas opens in summer 2026. For project teams targeting UKNZCBS conformity, there are three steps worth taking before.

1. Audit the high-impact materials in your project against EPD availability. Structure, envelope, and insulation typically account for the largest share of upfront carbon. Identify where manufacturer-specific data exists and where generic values are currently filling the gap.
2. Build EPD requirements into tender documentation and treat any substitution request as requiring a carbon data update, not just a cost assessment.
3. Ensure your whole life carbon assessment platform records data quality scores per material and produces output aligned with RICS WLCA v2, in a format suitable for submission to a verifier.

One Click LCA supports RICS WLCA v2-aligned whole life carbon assessments from feasibility through to as-built stage, drawing on a database of 500,000+ datasets that includes manufacturer-specific EPDs for construction products globally. For manufacturers who need to create verified product data for their own portfolios, One Click LCA's EPD generator produces EN 15804-compliant EPDs, reducing the time from data collection to published declaration and closing the data gap for specifiers who cannot find verified product data in the market.

FAQ

Q: What is an Environmental Product Declaration in construction?

An Environmental Product Declaration (EPD) is a standardised, third-party verified document that quantifies the environmental impact of a construction product across its life cycle. EPDs follow EN 15804 standard and are the primary data source for whole life carbon assessments under the RICS WLCA v2 standard. One Click LCA hosts 500,000+ datasets, including manufacturer-specific EPDs for UK construction products.

Q: Does the UKNZCBS explicitly require Environmental Product Declarations (EPDs)?

The UKNZCBS does not mandate EPDs directly, but they can be beneficial. It requires RICS WLCA v2-aligned whole life carbon assessment, which places manufacturer-specific EPDs at the top of its data hierarchy. Without them, conservative generic values apply, making it harder to meet the upfront carbon limit. According to One Click LCA, EPDs are the most effective mechanism for keeping assessed carbon aligned with what is actually built.

Q: Which life cycle stages does an EPD need to cover for UKNZCBS upfront carbon assessment?

For UKNZCBS upfront carbon (A1–A5), the relevant EPD data covers stages A1–A3: raw material extraction, manufacturing, and processing. Transport to site (A4) and construction installation (A5) are calculated separately using project-specific data. For life cycle embodied carbon reporting, stages C1–C4 are also relevant, though this remains a reporting-only requirement under Version 1.

Q: Can EPDs from overseas manufacturers be used in a UKNZCBS assessment?

Overseas EPDs can be used in a UKNZCBS whole life carbon assessment, provided they are EN 15804-compliant and third-party verified. The key consideration is whether declared values reflect the product as supplied to a UK project. Where an overseas EPD uses different transport assumptions, the A4 calculation should be adjusted for the actual delivery distance.

Q: Who is responsible for obtaining EPDs during the procurement process?

Responsibility sits with the design team and specifier. EPDs should be required at specification stage and confirmed through the tender process. Where a contractor proposes a product substitution, a current EN 15804-compliant EPD for the alternative should be required before updating the whole life carbon model. One Click LCA's EPD library supports specifiers in identifying verified product data.

Q: What happens if a key specified material does not have a manufacturer EPD?

Without a manufacturer EPD, assessors apply conservative generic database values, which typically overestimate impact and can push a project over its UKNZCBS upfront carbon limit. For high-impact materials, it is worth contacting the manufacturer directly. One Click LCA's EPD generator enables UK manufacturers to produce EN 15804-compliant EPDs, typically within a few weeks of data collection.