On most building projects, carbon gets counted near the end. The structure is settled, the façade is picked, and the cladding samples are on the table before someone runs the numbers. By then the report mostly describes decisions nobody can afford to undo. A team can swap one insulation product for another, but it can’t easily rethink a concrete frame that’s already been engineered, priced, and approved.
That’s backwards. The decisions that set most of a building’s carbon footprint are made in the first few weeks of design, when the team is still sketching options. Those decisions are also the cheapest to change.
Why the first sketches matter so much
Think about what’s still open at concept stage. How big should the building be? Can an existing structure be reused? Concrete, steel, timber, or a hybrid frame? How many basement levels? How much glass on the façade? How long should the spans be?
Each of those choices locks in a large amount of material, and with it a large amount of embodied carbon: the emissions from extracting, manufacturing, transporting, and installing everything the building is made of. Changing a column grid on a napkin sketch costs nothing. Changing it after the structural engineer has sized every member costs fees, time, and goodwill.
Later decisions still count. They just have less room to move. Picking a lower-carbon carpet tile is worth doing, but it won’t make up for an oversized basement full of reinforced concrete.
What changes when carbon is on the table from day one
When designers can see rough carbon figures next to cost and floor area during early design, the conversations change.
Reuse comes up first. If the site already has a building on it, an early carbon comparison often shows that keeping the existing structure saves more emissions than any new-build option can. Without that number in front of them, teams tend to assume demolition and start fresh.
Comparing a concrete frame, a steel frame, and a mass timber option side by side, early, lets the team weigh carbon alongside cost, fire strategy, and programme. A late assessment can only report on whichever system was already chosen.
Basements tend to shrink. Below-ground construction is carbon intensive because it needs so much concrete and steel. Seeing that impact early can prompt a rethink of parking needs or plant room locations.
Glazing gets more scrutiny too. Fully glazed façades carry a high embodied cost and often push up cooling loads too. An early check helps the team find a glazing ratio that suits daylight, views, and energy use.
Shorter or more regular spans can cut the amount of structure needed. Engineers can test this cheaply at concept stage and expensively at detailed design.
You don’t need perfect data to start
A common objection is that a carbon assessment needs a finished design and a full bill of materials. A detailed life cycle assessment does. An early-stage estimate doesn’t.
At concept stage, rough quantities and industry-average carbon factors are enough to compare options and see which one is clearly better, by roughly how much, and where the biggest sources sit. A 20% difference between two structural schemes shows up just as clearly in a rough estimate as in a detailed one.
Several tools are built for exactly this. The AIA-CLF Embodied Carbon Toolkit for Architects, published by the American Institute of Architects and the Carbon Leadership Forum, explains the basics of measuring and reducing embodied carbon and points to calculators designed for early design-stage analysis. Some of these need only basic inputs like building height, floor area, and structural system to produce a first estimate.
As the design develops, the team can refine the model with real quantities and product-specific Environmental Product Declarations. The early estimate doesn’t get thrown away. It becomes the baseline that later stages are measured against.
Making it part of the process
Early carbon thinking works best when it’s built into how the team already works. A few habits help.
Set a target at the brief stage. A carbon budget per square meter, agreed with the client alongside the cost budget, gives the team something concrete to design toward.
Run a quick comparison at each design milestone. A one-page summary showing how the current scheme compares with the target, and which elements contribute most, keeps carbon visible without slowing anyone down.
Bring the structural engineer in early. Structure is usually the largest single source of embodied carbon, and the engineer’s input at concept stage is worth far more than a late value-engineering exercise.
Talk to the client in their terms. Many owners now face carbon disclosure rules, investor questions, or tenant expectations. Showing that early carbon decisions also reduce material quantities, and often cost, makes the case easier.
Include operational energy in the same conversation. Embodied and operational carbon sometimes pull in different directions. Extra insulation adds embodied carbon but cuts energy use for decades. Looking at both together, early, helps the team find the right balance for the building’s expected life.
The payoff for the building and the people who use it
Choices made with carbon in mind often lead to buildings that work better in other ways too. Reused structures keep character and history in a neighbourhood. Leaner structural systems can open up floor plates. A sensible glazing ratio improves thermal comfort and reduces glare. Timber structures are often praised by occupants for how they look and feel.
And because the carbon released during construction happens now, during the years when cutting emissions matters most, the early decisions have an outsized effect on the climate. Operational emissions can be reduced later by upgrading systems or switching to cleaner power. Embodied carbon can’t be taken back once the building is up.
Where to start on your next project
If your team currently measures carbon only at the end, try one change on the next project: run a rough comparison of two or three massing or structural options during concept design, and put the results next to the cost plan. It can be rough, as long as it happens while the options are still open. Once the numbers sit beside the cost plan, they start shaping decisions that used to be made on habit.
