- 1Five areas suffice: functional unit, modules A1-D, verification, validity, A1 or A2 version.
- 2Modules A1-A3 (production) carry most of the impact in Ic Construction.
- 3No FDES available: the engine automatically applies the DED +30% penalty.
- 4An individual FDES reflects your performance; a collective declaration includes a +10 to 20% margin.
1A declaration's journey: from INIES to the Ic Construction calculation
All environmental data entering an RE2020 calculation follows the same path. The engineering consultancy starts with the INIES database, selects the FDES for the specified product, imports it into its calculation software (Pléiades, Cypebat, Lesosai, Archiwizard), enters project quantities, and obtains the Ic Construction indicator in kg CO₂ equivalent per m² SHAB. This process is fixed by the ministerial order of 4 August 2021: only a declaration registered in INIES is admissible, and only a third-party verified declaration can be used without weighting.
From an INIES FDES to the Ic Construction verdict
The path of environmental data from the INIES database to the regulatory RE2020 calculation. Five steps, one calculation tool, and a verdict determining the building permit.
For an engineering consultancy discovering this workflow, two common pitfalls should be understood from the first project. First: the declaration version. An EN 15804+A1 FDES can no longer be used: these declarations were withdrawn from INIES on 1 July 2026, and only EN 15804+A2 FDES are now valid under RE2020. If an older dossier still contains an A1 declaration, it must be replaced with its A2 version. Second: the functional unit. Two FDES are comparable only if they share the same functional unit (1 m² installed, 1 linear metre of joinery). Comparing a m² of concrete with a m³ of insulation makes no sense.
2Anatomy of an FDES: the five areas to read
An FDES runs to 30 to 80 pages, with a standardised structure: five areas in this order. If you can identify these five sections in any INIES declaration, you know how to use it in an Ic Construction calculation.
Read an FDES in 5 minutes flat
The five areas an engineering consultancy reviews to qualify an FDES, and what it specifically looks for in the RE2020 Ic Construction calculation. Click a declaration section to see what the consultancy reads first.
Product name, manufacturer, commercial reference, INIES FDES number, version (A1/A2), expiry date.
The infographic below reproduces a typical declaration layout. Click each section to see what an engineering consultancy reads first - in less than 30 seconds per area, it has everything needed to decide whether the declaration is usable or an alternative is needed.
3Modules A1 to D: which count for RE2020
EN 15804+A2 PCR organises impacts into 5 main phases and 17 modules. They do not all carry the same weight in the Ic Construction calculation. The RE2020 engine includes modules A (production + construction site), modules B1 to B4 (use in the building, including replacements in B4), modules C (end of life), and module D (benefits beyond the system, such as material recovery). Energy consumption in use (B6) falls under the separately calculated Ic Énergie indicator: modules B5 to B7 in declarations are therefore not counted in Ic Construction.
The 5 cradle-to-grave phases
A construction product's LCA comprises 17 modules grouped into 5 main phases. RE2020 draws on the whole, with a strong focus on A1-A3 (production) and A4-A5 (construction site).
This distribution matters for product strategy. A product whose dominant impacts fall in A1-A3 (production) - for example concrete with a high clinker content - contributes heavily to Ic Construction. A heat pump contributes to the 2 indicators: manufacturing, replacements and refrigerant leaks count in Ic Construction, while electricity consumed during use falls under Ic Énergie. For the engineering consultancy, this means optimisation levers differ by work package: cutting concrete and choosing bio-based insulation for Ic Construction, equipment energy performance for Ic Énergie.
Module D deserves particular attention. It accounts for benefits and loads beyond the system: material recycling, energy recovery at end of life, reuse. It is published separately from the other modules in the declaration, and is not added to Ic Construction in its raw form - it enters weighted by RE2020 rules. For bio-based insulation with good recovery at end of life, module D can be strongly negative (therefore a benefit), but this benefit is not directly visible in the score displayed by Pléiades.
4How much impact does 1 m² have? The mini-calculator
To ground the explanation in real orders of magnitude, here is a mini-calculator simulating a product's contribution to your Ic Construction. Five construction archetypes (concrete slab, bio-based insulation, aluminium joinery, heat pump, plasterboard), with their INIES 2026 median values, three declaration types (individual, collective, DED), and a quantity slider. The verdict appears in kg CO₂ eq., with a module breakdown and comparison against the DED penalty.
How much does your declaration choice affect the carbon calculation?
Three steps to estimate a product's contribution to your Ic Construction. Median INIES 2026 values - indicative, does not replace a Pléiades calculation for a real project.
Savings vs default DED: 2,898 kg CO₂ eq. This is what you gain in your Ic Construction calculation by using this declaration rather than default data.
5Default scenarios, DED, configurable FDES: the grey areas
RE2020 calculations have three blind spots that every engineering consultancy encounters in real life. Knowing them helps anticipate surprises at review, and guide the project owner towards the right specifications from DCE stage.
The grey areas of the RE2020 calculation
Three situations every engineering consultancy encounters in real life - and which the Ic Construction calculation does not treat in the same way. Anticipating them avoids surprises during checks and helps guide the client towards the right specifications.
Default scenarios
For modules B (use) and C (end of life), the manufacturer does not know the product's actual history with the user. The EN 15804+A2 PCR therefore provides prescribed scenarios: average transport of 100 km, average recycling rate, etc. These scenarios are the same for everyone - you cannot circumvent them.
The DED penalty +30%
When no FDES or PEP is available for an installed product, the calculation switches to Default Environmental Data published by the ministry. These DED incorporate an automatic uplift of 30% - a conservative penalty that mechanically worsens the Ic Construction score. As a result, a project mainly using products without FDES can lose an entire threshold class.
Configurable FDES
A recent variant of collective FDES. The manufacturer publishes a configurable declaration that adjusts to the actual order (insulation thickness, joinery dimensions, finish). The engineering consultancy enters the parameters in the calculation software, which automatically interpolates the indicators. Very useful for extensive catalogues where one FDES per product reference would be impractical.
First blind spot: default scenarios prescribed by EN 15804+A2 PCR. For modules outside the manufacturer's control (transport to site, product end of life), the PCR sets standardised assumptions - typically 100 km of road transport, average sector recycling rate. These scenarios are the same for all declarations under the same PCR; you cannot bypass them, and a manufacturer delivering 30 km away cannot claim this benefit in a standard FDES.
Second blind spot: the DED +30% penalty. When a product specified in a project has no usable FDES or PEP in INIES, the calculation switches to the Default Environmental Data (DED) published by the ministry. These DED include an automatic 30% uplift - a conservative margin that mechanically worsens the Ic Construction score. In a project with a high DED share, the additional carbon impact can suffice to lose a whole RE2020 threshold class.
Third, more positive case: configurable FDES (or parameterised declarations). This is a recent variant where the manufacturer publishes one declaration parameterised by the order (thickness, finish, length, opening). The engineering consultancy enters the parameters in its calculation software, and the engine automatically interpolates the indicators. Very useful for extensive joinery or covering catalogues where each reference does not justify a dedicated FDES.
6What to do with an expired FDES or one without third-party verification
An FDES is valid for 5 years from publication. After this, the Pléiades / Cypebat calculation engine no longer accepts it without weighting - it automatically switches to DED status, with its 30% penalty. For an engineering consultancy finding an expired declaration during construction, there are two options: find a recent alternative declaration for the same or an equivalent product, or ask the manufacturer to renew the declaration (which can be quick if the upstream LCA is already current).
A subtler case: a declaration without third-party verification. Before the ministerial order of 4 August 2021, manufacturers' self-declared documents circulated. Since that order, only declarations verified by a third party through an accredited body (CSTB, Bureau Veritas, others) are admissible without penalty in an Ic Construction calculation. Older self-declared documents are no longer usable - they have gradually been withdrawn from INIES or reclassified.
The right habit at DCE stage: extract from INIES the list of valid declarations for decisive work packages (concrete, insulation, joinery), check validity dates against the planned construction date, and alert the project owner to potential gaps. This 2 to 3 days of upstream work prevents weeks of recalculation at EXE stage.
7Key takeaways
Reading an FDES usefully means knowing where to look. Five critical sections, two recurring pitfalls (A1 vs A2 version, third-party verification), and three grey areas (default scenarios, DED +30%, configurable declarations) suffice to use any INIES declaration in less than 5 minutes.
Three angles for mastering environmental declarations in the building sector
This article is part of a series of three publications covering FDES from three complementary angles: understanding the ecosystem, choosing the declaration on the manufacturer side, and operational use on the engineering consultancy side.
EPD, FDES, PEP, LCA: understanding environmental declarations
The complete overview of the 4 acronyms that structure environmental data for buildings.
FDES, EPD, PEP: choosing and publishing the right declaration for your product
The supply-side decision-maker: individual vs collective, cost, lead time, ROI on a differentiating product.
An engineering consultancy spending 3 days at DCE stage mapping available FDES saves several weeks at EXE stage.
For more on choosing the right declaration format as a manufacturer, see FDES, EPD, PEP: choosing and publishing the right declaration for your product. For the LCA fundamentals underpinning every environmental declaration, see How to make your first product LCA a success.
