Giulio Pisciotti, Technical Advisor, from our in-house Innovation & Design team discusses how its recent Slab Carbon Matrix research, explores how different slab systems and grid sizes influence embodied carbon in office buildings
How much does span really cost in carbon? Span length is often driven by functionality, efficiency, or commercial considerations - but its carbon implications are rarely made fully visible at concept stage.
Our in-house Innovation & Design team researched and analysed the embodied carbon performance of multiple slab systems used in office buildings - testing how they behave across increasing grid sizes and comparing them under identical layout conditions.
Results
1: Carbon vs. Grid Size - The Span Penalty
As spans increase, embodied carbon does not rise linearly - it accelerates.
Some systems show sharp carbon escalation beyond certain thresholds, while others demonstrate more stable growth.
Key Insights
Longer spans quickly erode carbon efficiency. What appears to be a modest grid increase can trigger a disproportionate rise in material demand, and therefore carbon.
2: System vs System – Same grid, different outcomes
When comparing systems at identical grid sizes, the carbon spread between structural typologies becomes significant.
At the same span:
• Some systems consistently outperform others in kgCO₂e/m²
• Material intensity- not just material type - drives performance
• Optimisation potential varies dramatically depending on the structural concept
There is no universally low-carbon slab, only context-specific efficiency.
What does this mean for design teams?
• Grid strategy is a carbon strategy
• Structural typology can shift embodied carbon by a meaningful margin
• Early-stage structural decisions carry long-term carbon consequences
• There is a definable ‘sweet spot’ for each system, beyond which carbon performance deteriorates rapidly.
If we want to reduce embodied carbon in offices, structure cannot be a downstream decision. Early structural decisions and grid strategy matters. The cheapest carbon is the one you never design in.
If you have any further queries on our Slab Carbon Matrix research please reach out to our Innovation and Design team.
