Embodied Carbon: Our Guide to Measuring Construction Project Emissions

If you’re working in the built environment, you might be noticing a shift: tender documents are asking for “whole life carbon” numbers. Tier 1 contractors want embodied carbon data from their subcontractors. Some councils now require carbon assessments as part of planning. But at the same time, there’s still no single national requirement in the UK telling everyone exactly what to do and when. And when you're asked for "project lifecycle emissions" or something similar, then working out what to include, and how to measure it, can be overwhelming.

This guide is here to make that feel a lot more manageable.

Why Account for Embodied Carbon in Construction Projects?

Globally, the built environment is estimated to account for around 38–39% of energy-related emissions, once you include both operational and embodied carbon. Evidence from the UK suggests that embodied carbon alone can make up a very large share of a new building’s total lifetime emissions – in some cases, up to 70%.

That’s why the industry is moving towards wider reporting, with regulation catching up in some areas. For example, in the UK:

Nationally, there’s no single, binding regulation that says “you must measure embodied carbon for all projects”.
However, locally, the picture is changing fast.
- The London Plan requires Whole Life-Cycle Carbon (WLC) assessments for referable planning applications, and encourages them for other major developments.
- Councils like Westminster now require WLC assessments for major redevelopment schemes with substantial demolition, and encourage them for other major projects.
- Other authorities are following suit with their own guidance and validation lists.

But even if you’re not legally required to do this on every project today, the direction of travel is clear:

Tier 1 contractors are baking carbon expectations into frameworks and supply chain requirements.
Clients want evidence that projects are genuinely aligned with net zero commitments.
Local authorities increasingly see whole life carbon assessments as part of “good practice” design and planning.

If you’re a contractor, consultant, architect or specialist supplier, it’s no longer a question of if you’ll be asked for project carbon numbers – but when and how often.

Project-level footprints vs organisational footprints

If you already report a corporate footprint, you’re probably familiar with Scopes 1, 2 and 3 under the GHG Protocol – fuel use, purchased electricity, business travel, purchased goods and services, and so on. That’s an organisational view: emissions linked to your company over a year.

A construction project emissions assessment takes a different angle:

The asset is the unit of analysis (a building, infrastructure asset, fit-out, or retrofit).
You measure emissions over a defined life cycle – from raw materials, to construction, to use, to end of life.
Results are usually expressed as a total for the project, or as a functional unit, e.g. kgCO₂e per m².

The RICS WLCA standard (covered below) explicitly connects project life cycle stages with corporate scopes, so the data you collect for a project can support both project-level reporting and your wider organisational footprint.

In practice, that means:

Your project team sees carbon in a familiar way – linked to materials, quantities and construction activities.
Your sustainability or finance team can still map that data back into Scope 3 categories and net zero targets.

What is Embodied Carbon Within Construction?

To have a sensible conversation about embodied carbon, you need a bit of life cycle language. That’s where BS EN 15978 comes in – the European standard that sets out how to structure a building’s life cycle into modules.

BS EN 15978: The European Standard

You’ll often see diagrams that look like a row of boxes labelled A, B, C and D. In short:

Product stage (A1–A3) – often called cradle to gate

A1: Raw material supply
A2: Transport to manufacturer
A3: Manufacturing

Construction stage (A4–A5) – extends to cradle to site

A4: Transport to site
A5: Construction and installation (including site activities and waste)

Use stage (B1–B7) – the building in operation

B1: Use
B2–B5: Maintenance, repair, replacement, refurbishment
B6: Operational energy use
B7: Operational water use

End-of-life stage (C1–C4) – grave

C1: Deconstruction / demolition
C2–C4: Transport, processing and disposal

Module D – beyond the system boundary

Potential benefits or loads from reuse, recovery and recycling after the asset’s life

You’ll also hear:

Cradle to gate → typically A1–A3
Cradle to site → typically A1–A4
Cradle to grave → A1–C4
Cradle to cradle or +D → A1–C4 plus Module D

How do the lifecycle stages map onto "upfront" embodied carbon?

“Upfront embodied carbon” is the carbon emitted before the building's use is considered – in other words, Modules A1–A5.

This is where a lot of the emissions are locked in before anyone even moves in. You can optimise future maintenance and operational energy later – but you can’t un-pour a slab or un-fabricate a steel frame once it’s up.

That’s why many clients, councils and Tier 1 contractors are now asking specifically for A1–A5 assessments alongside or as a first step toward full whole life carbon assessments.

RICS WLCA: the playbook most people now follow

The RICS Whole Life Carbon Assessment for the built environment (2nd edition) sits on top of the BS EN 15978 framework and turns it into a practical standard.

A few key points:

It applies across buildings and infrastructure, globally.
It became fully effective for RICS members on 1 July 2024, replacing the 1st edition.
It sets expectations for:
- System boundaries and life cycle stages
- Data quality and hierarchies
- How to treat things like grid decarbonisation and future scenarios
- How to report results and confidence levels

If you’re a RICS member, you’re expected to follow the 2nd edition when carrying out carbon assessments. If you’re not, aligning with RICS WLCA is still a very good way to show your work is credible and consistent.

How to actually measure upfront embodied carbon (A1–A5)

Let’s make this practical, focusing on modules A1-5 (upfront embodied carbon). Here’s what measuring upfront embodied carbon typically looks like on a project.

1. Be explicit about your scope

Write this down at the start:

What asset? (e.g. “New-build six-storey office, 12,000 m² GIFA”, “Warehouse with mezzanine”, “Residential block of 80 units”)
Which modules? In this case, you’re focusing on A1–A5, but note if any B or C stages are included.
What’s in and out of scope? Are temporary works, external works, site cabins, landscaping included?

Being clear upfront avoids arguments later and makes your outputs much more useful.

2. Get a solid quantities baseline

For A1–A5, quantities are the backbone. You’ll usually work from:

Bills of quantities / cost plans
Designs and drawings
Schedules (e.g. of finishes, MEP equipment)

The aim is to translate cost or geometry into a list of materials and components with quantities in relevant units (m³, tonnes, m², units).

You don’t need to model every screw, but you do need to capture the major contributors, such as:

Concrete (by mix and strength where possible)
Reinforcement and structural steel
Masonry, timber, insulation, roofing build-ups
Cladding and glazing systems
Internal partitions, ceilings and key finishes

Even if your first pass is coarse (e.g. “generic concrete, 30 MPa”), that’s fine – you can refine material types and EPD selections later.

3. Apply the RICS data hierarchy for A1–A3

For the product stage (A1–A3), you turn those quantities into carbon by applying emission factors (kgCO₂e per unit). RICS WLCA sets out a data hierarchy and asks you to assess confidence in each data source.

In plain terms, you should try to use:

Product-specific EPDs (best where available)

Verified Environmental Product Declarations to EN 15804
Specific to a manufacturer and product.
Ideal for high-impact elements (e.g. façade systems, structural systems, insulation products).

Manufacturer-average or collective EPDs

Represent a group of products or plants from a manufacturer or association.
Useful where the exact product isn’t fixed, but you know the type and performance requirements.

Generic embodied carbon datasets

National / regional LCA databases or tool-specific datasets.
Can be aligned with EN 15804 and BS EN 15978 but not brand-specific.

The ICE Database and similar resources

The Inventory of Carbon and Energy (ICE) is a widely used, free database of embodied carbon factors for many common construction materials, originally compiled by the University of Bath and now maintained by Circular Ecology.
Very helpful for early-stage or where EPD coverage is patchy, but data may be older or more generic than product-specific EPDs.

Other emission factor databases

Sources like DEFRA and others focus primarily on organisational carbon footprinting, but if no other EPD-based sources are available, then these can be used.
In practice, DEFRA would only be used for A4 and A5 below; A1-3 is usually covered by sources higher up in the hierarchy.

As data becomes more specific, your confidence generally increases. RICS WLCA encourages you to record data sources and quality so you (and others) can see where refinements would have the biggest impact.

4. A4 – transport to site

Here you’re trying to capture emissions from transporting construction products from the factory or distribution hub to site. In an ideal world, you’d know:

Origin of each product or material
Mode of transport (HGV, rail, shipping)
Distances involved

In reality, you’ll mix project-specific information (for local suppliers where you know the route) with default assumptions. The RICS WLCA and various tools provide typical transport distances and modes you can use where detailed data isn’t available.

If you're transporting the products yourself, this stage is easier: you can simply track your mileage (or even better, fuel usage) and use emissions factors to convert this data. DEFRA in the UK is the main source for this.

5. A5 – construction and installation

Module A5 captures what happens on site:

Energy and fuel use by plant, generators and temporary services
Site electricity consumption
Construction waste (offcuts, breakages, packaging, over-ordering) and how that waste is handled
Ancillary materials with significant mass (e.g. formwork, large temporary works if not reused multiple times)

Data can come from:

Site fuel and electricity records
Waste transfer notes and skip weights
Contractor’s environmental plans

Where that level of detail isn’t realistic, especially at early design stages, you can use:

Default waste rates for different materials (e.g. 5–10% depending on trade)
Benchmarked site energy per m² for similar projects

Again, the important thing is to declare your approach and data quality, not to pretend the data is perfect.

Data sources you’re likely to use

Here are the main carbon factor sources you’ll encounter and how they tend to fit into a workflow.

Environmental Product Declarations (EPDs)

Pros

Standardised format, usually following EN 15804.
Often provide emissions across A1–A3 and sometimes A4–C4.
Great for comparing design options within a product family (e.g. different insulation materials, façade systems).

Cons

Coverage is uneven – some product categories have lots of EPDs, others very few.
EPDs are specific: if a product changes, the EPD can become outdated.

The ICE Database

The ICE database is, essentially, a big table of embodied carbon factors for common construction materials, made freely available and widely referenced in guidance and tools.

Pros

Good coverage for widely used materials (concrete, steel, common metals, masonry, some plastics and timber).
Free, and well-understood across the industry.

Cons

Primarily focused on embodied carbon; it doesn’t try to be a full multi-impact LCA.
Some entries are based on older data or broad averages; they don’t replace good quality EPDs where those exist.

Built Environment Carbon Database (BECD)

The Built Environment Carbon Database (BECD) is a UK-wide platform created to store and share whole life carbon data for construction products and projects.

Pros

Free to use, with growing coverage of both project-level and product-level data.
Designed to align with RICS WLCA and other industry initiatives.

Cons

Still evolving; data completeness and granularity vary depending on who’s contributed.

Tool-specific databases

Many commercial LCA or carbon tools bundle databases that combine:

EPD libraries
Generic datasets
Default transport assumptions

These can save time but are only as good as their underlying data and how transparent they are about sources. Whatever you use, it’s good practice to:

Record which database and version you relied on
Check whether it aligns with RICS WLCA expectations
Use external sources (like ICE or BECD) as a sense-check when numbers look odd

Making project-level emission measurement more manageable

A lot of teams worry that “doing carbon properly” will slow everything down. In reality, you can start fairly light and build maturity over time.

A few practical tips:

Start where you have the most influence. Focus first on materials and elements that drive the bulk of A1–A5 emissions (e.g. concrete, steel, large façade and roof build-ups).
Match the method to the design stage. Early on, use simpler quantities and more generic factors. As design freezes, swap in product-specific EPDs where they add real value.
Bake data collection into normal workflows. When you’re sending out procurement packages, ask for EPDs and carbon data alongside technical and cost information.
Be transparent about uncertainty. A first-pass estimate with clear assumptions is far more useful than a “perfect” assessment that never happens.

The aim isn’t to turn project teams into LCA specialists overnight. It’s to make carbon a normal design parameter, like cost or programme – especially during decisions that lock in high upfront embodied emissions.

How Seedling can help

If all of the above feels like a lot to hold in your head while also juggling design changes, cost pressures and programme, you’re not alone. That’s exactly why we built tools for this.

At Seedling, we have a project emissions tool which aligns to RICS and measures upfront embodied carbon (A1–A5), creating shareable reports in minutes.

In practice, that means you can:

Structure your project data around the same modules and language you’re seeing in RICS WLCA and council guidance.
Focus on the key materials and elements that drive upfront embodied emissions.
Quickly generate clear, client-ready outputs that explain what’s in scope, what data sources you’ve used, and where the main hotspots sit – without needing to build a complex spreadsheet or LCA model from scratch.

Importantly, we design everything to feel manageable for busy teams. You don’t need to be an embodied carbon expert to get started; you just need a project and some basic quantities.

If you’d like support on:

Setting up a simple, repeatable way to measure A1–A5 across your projects
Aligning your project assessments with both RICS WLCA and your wider organisational footprinting
Turning carbon numbers into clear, confident communication with clients, planners and Tier 1 partners

…Seedling can help you get there – without making carbon accounting feel like a separate, intimidating discipline.