---
title: "A Contractor's Carbon Footprint, Worked End to End"
description: "One quarter on one site, from logged quantities to a Scope 1, 2
  and 3 split: every input, every factor, the arithmetic, and what the numbers
  do not tell you."
metaTitle: "Worked Example: A Contractor's Carbon Footprint"
category: Fundamentals
date: 2026-10-20
dateModified: 2026-10-20
readingTime: 8 min read
lead: Most carbon guidance stops at the method. This is one quarter on one
  site worked all the way through — the quantities, the DEFRA factor applied
  to each, the Scope 1, 2 and 3 split that comes out, and the three things the
  total cannot tell you.
cardDescription: One quarter on one site, worked end to end — quantities,
  factors, arithmetic, the Scope split, and the limitations. Every figure
  calculated with the same factor set the product uses.
ctaHeading: Produce this from your own site data
ctaBody: VerdCore logs these quantities as work happens and applies the same
  DEFRA factor set used throughout this example, so the Scope split is an
  export rather than a spreadsheet exercise.
footerNote: This is a modelled example, not a real client project. The
  quantities are illustrative; the emission factors and the arithmetic are
  real. Always check figures against the current DEFRA/DESNZ conversion
  factors for your reporting year.
ogTitle: "Worked Example: A Contractor's Carbon Footprint"
ogDescription: One quarter on one site from logged quantities to a Scope 1, 2
  and 3 split — every factor, the arithmetic, and the limitations.
faq:
  - q: Is this a real project?
    a: No. The quantities are modelled on a small reinforced-concrete frame job and are illustrative. The emission factors, the conversion arithmetic and the Scope classifications are real, and are the same ones VerdCore applies to live data.
  - q: Why is Scope 3 so much larger than Scope 1 and Scope 2?
    a: Because embodied carbon in materials dwarfs site energy on most construction projects. In this example Scope 3 is 92.3% of the total and steel alone is 62.7%, while all the diesel, gas and electricity together come to 7.8%. A Carbon Reduction Plan reporting only Scope 1 and Scope 2 would show 15.2 tCO2e against an actual 196.8 tCO2e.
  - q: Which emission factors does this use?
    a: The UK Government DEFRA/DESNZ greenhouse gas conversion factors for the 2026 reporting year, applied by the year of the entry date. Red diesel uses the Gas oil row rather than road diesel, and road transport uses per-vehicle-mile figures rather than per-tonne-kilometre.
  - q: What does a total like this not tell you?
    a: Three things. It is a snapshot of one quarter, not an annual baseline. It covers one site, where a Carbon Reduction Plan must report the whole organisation. And some material factors are cradle-to-gate industry averages rather than product-specific EPDs, so a figure for a given material can move substantially once real EPD data replaces the average.
---

Carbon guidance tends to stop at the method: measure, convert, report. What it rarely shows is a complete set of numbers with the working left in, which is the only way to see where a footprint actually comes from and how wrong the common shortcuts are.

So here is one quarter on one site, worked all the way through. **The quantities are modelled** — this is not a real client project — but every factor, every conversion and every scope classification is real, and they are the same ones applied to live data.

The project: a small reinforced-concrete frame job, one site, one quarter.

## Step 1 — the quantities

This is the whole input. Nothing else goes in.

| Logged | Quantity | Category |
| --- | --- | --- |
| Red diesel — excavator, dumpers, telehandler | 4,200 litres | Fuel |
| Road diesel — two site vans | 900 litres | Fuel |
| Site cabin heating | 3,100 kWh | Fuel |
| Mains electricity — cabins, tower light, small plant | 5,400 kWh | Fuel |
| Ready-mix concrete — foundations, slabs, frame | 310 tonnes | Materials |
| Rebar and structural sections | 42 tonnes | Materials |
| Formwork and carcassing timber | 18 tonnes | Materials |
| HGV deliveries to site | 3,800 miles | Transport |
| Concrete and inert waste | 85 tonnes, recycled | Waste |
| Mixed waste | 24 tonnes, landfill | Waste |
| Timber waste | 12 tonnes, recycled | Waste |
| Plasterboard waste | 6 tonnes, recycled | Waste |

## Step 2 — the conversion

Each quantity is multiplied by the DEFRA/DESNZ conversion factor for its row, in the factor set for the year of the entry. Two of these are worth pausing on, because both are common errors.

**Red diesel is not road diesel.** DEFRA lists it as *Gas oil*, a separate row. Using the road diesel factor under-reports plant fuel by about 8%, and plant fuel is usually the largest Scope 1 source on a construction site.

**Road transport factors are per vehicle-mile, not per tonne-kilometre.** The two are not interchangeable, and mixing them up can be an order-of-magnitude error.

| Entry | Quantity | kgCO₂e |
| --- | --- | --- |
| Red diesel | 4,200 L | 11,572.7 |
| Road diesel | 900 L | 2,325.2 |
| Site cabin gas | 3,100 kWh | 626.2 |
| Mains electricity | 5,400 kWh | 707.2 |
| Concrete | 310 t | 35,433.0 |
| Steel | 42 t | 123,480.0 |
| Timber | 18 t | 4,851.1 |
| HGV deliveries | 3,800 mi | 5,174.0 |
| Concrete waste, recycled | 85 t | 86.2 |
| Mixed waste, landfill | 24 t | 12,493.9 |
| Timber waste, recycled | 12 t | 55.8 |
| Plasterboard waste, recycled | 6 t | 27.9 |

## Step 3 — the Scope split

This is the output a Carbon Reduction Plan actually needs. The classification rule is what does the work here: **Scope 1 is fuel you burn**, **Scope 2 is energy you buy that someone else burns**, and **Scope 3 is everything else in the value chain**.

Note where the site cabin gas lands. It is Scope 1, not Scope 2, because you burn it yourself — purchased electricity is the only Scope 2 line on most construction sites.

| Scope | kgCO₂e | Share |
| --- | --- | --- |
| **Scope 1** — red diesel, road diesel, cabin gas | 14,524 | 7.4% |
| **Scope 2** — purchased electricity | 707 | 0.4% |
| **Scope 3** — materials 163,764 · transport 5,174 · waste 12,664 | 181,602 | 92.3% |
| **Total** | **196,833** | **196.8 tCO₂e** |

## What the numbers actually say

**Scope 3 is the footprint.** At 92.3% it is not a supplementary disclosure, it is the answer. A plan reporting only Scope 1 and Scope 2 — the single most common reason a CRP is marked non-compliant — would show **15.2 tCO₂e against an actual 196.8**, understating the project by 92%.

**One material is most of it.** Steel is 42 tonnes out of 370 tonnes of material, 11% by weight, and **62.7% of the entire footprint**. Any reduction measure that does not touch steel specification or reuse is rearranging the remaining third.

**One skip dominates the waste line.** Mixed waste is 24 tonnes of the 127 tonnes removed from site, 19% by weight, and 98.7% of the waste emissions — because unsegregated waste goes to landfill and landfill is where the factor jumps. Diverting the timber alone avoided 11,049 kgCO₂e against sending it to landfill, which is a bigger saving than the entire site electricity bill.

That last point is the practical one: segregation is a skip-hire decision, not a design decision, and it is available this week.

## Step 4 — what this total does not tell you

A number without its limits invites misuse, so here are the three that matter.

**It is one quarter, not a baseline.** A Carbon Reduction Plan reports against a fixed baseline year. This is a single reporting period on a single project, and seasonality alone moves the gas and electricity lines.

**It is one site, and a CRP is organisational.** [PPN 006](/resources/ppn-06-21-explained.html) requires your company's total emissions, not a project's. Office energy, the full fleet, business travel and employee commuting are all in scope for the plan and absent here.

**Some material factors are industry averages, not your product.** Cradle-to-gate averages are the right default when no better data exists, but a specific product's EPD can differ substantially — and for a few materials DEFRA publishes no factor at all, so a secondary source has to be used and declared. We documented exactly which ones and why in our [investigation into the gaps in DEFRA's factor set](/resources/defra-emission-factors-secondary-sources.html). For a figure going into a tender, an EPD for the steel would be the single highest-value improvement to this example — it is 63% of the total resting on an average.

## The point of working it through

Two conclusions survive from this, and neither is visible from the method alone: **the footprint is in the materials, and the reporting risk is in the scope you skip.** Both come out of the arithmetic rather than from guidance.

Keeping quantities logged as work happens, rather than reconstructing them from invoices at tender time, is what makes the exercise repeatable — the same discipline behind [producing a Carbon Reduction Plan](/resources/how-to-write-a-carbon-reduction-plan.html) that holds up when a buyer reads it, and what [construction carbon reporting software](/construction-carbon-reporting-software.html) is for.