# What does embodied carbon A1-A3 mean, and what do modules A4 to D add?

Canonical: https://senseible.earth/answers/what-is-embodied-carbon-a1-a3

A1-A3 is the product stage of a construction product: raw material supply (A1), transport to the factory (A2) and manufacturing (A3). It is the cradle to gate figure on most EPDs. Modules A4 to C4 add transport to site, construction, use and end of life, and module D reports reuse and recycling benefits separately.

## The modules in EN 15804

EN 15978 uses the same modules to add up a whole building, which is why architects ask suppliers for figures by module.

- A1 to A3, product stage: raw materials, inbound transport, manufacturing.
- A4 to A5, construction stage: transport to the building site, installation and site waste.
- B1 to B7, use stage: use, maintenance, repair, replacement, refurbishment, operational energy (B6) and operational water (B7).
- C1 to C4, end of life stage: demolition, transport, waste processing, disposal.
- D, beyond the system boundary: net benefits and loads from reuse, recovery and recycling.

## What an EPD must declare

Under EN 15804+A2, most EPDs must declare A1 to A3, C1 to C4 and D. A4 onwards in A and B are optional because they depend on the project. Climate impact is shown as GWP in kg CO2e per declared or functional unit, split into fossil, biogenic and land use parts plus a total.

A1-A3 can be shown as one aggregated figure. That is the number most tender documents and embodied carbon tools take first.

## Why module D is kept apart

Module D credits future recycling, for example steel scrap replacing new steel. It is reported next to the life cycle, not added into it, because the benefit happens outside the building and depends on future practice. Do not subtract D from A1-A3 when you compare products.

## Where a plant's own data fits

A3 is the part a manufacturer controls most directly: the fuel and electricity used on site, plus process emissions. A1 needs supplier data or database figures for raw materials. A2 needs inbound freight. A full EPD also needs a product category rule, an LCA to EN 15804 and independent verification by a programme operator.

## Worked example: the energy part of A3 for a tile plant

- Monthly output: 500 t of tiles
- Grid electricity: 50,000 kWh x 0.710 = 35,500 kg CO2
- Diesel for forklifts and a standby generator: 2,000 L x 2.68 = 5,360 kg CO2
- A3 energy emissions: 35,500 + 5,360 = 40,860 kg CO2
- Per tonne: 40,860 / 500 = 81.7 kg CO2 per tonne

This covers only on-site energy. Process emissions, packaging and the A1 and A2 stages must be added for a complete A1-A3 figure.

## What Senseible does here

Senseible can give you the on-site energy share of A3 from your plant's fuel invoices and electricity bills, traced line by line. It does not run EN 15804 LCAs or publish EPDs.

- [Construction sector accounting guide](https://senseible.earth/industries/construction)
- [How to read GWP on an EPD](https://senseible.earth/answers/how-to-read-gwp-on-an-epd)
- [Embodied carbon from quantities](https://senseible.earth/answers/how-to-calculate-embodied-carbon-from-quantities)
- [Cradle to gate or cradle to grave?](https://senseible.earth/answers/cradle-to-gate-or-cradle-to-grave)

Sources: [EN 15804:2012+A2:2019 and ISO 21930:2017, core rules for EPDs of construction products (iso.org for ISO 21930)](https://www.iso.org), [IPCC 2006 Guidelines, Volume 2 Energy](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html)

Last reviewed 2026-10-15.