The impact of building elements and whole-building carbon benchmarking studies

The RIBA 2030 Climate Challenge Target Benchmarks Review is pursuing significant embodied carbon reductions in the built environment. As per the London Energy Transformation Initiative (LETI) Embodied Carbon Primer report, it aims to almost halve embodied carbon benchmarks for residential and non-residential buildings from 1750 KgCo2e/m2 and 1700 KgCo2e/m2 to 850 KgCo2e/m2 and 840 KgCo2e/m2 respectively. 

Every building’s embodied carbon footprint is unique — influenced by a multitude of factors, such as construction materials, building use, energy sources, and the efficiency of its design. The first step to reducing your project’s embodied carbon is understanding and addressing its sources. Ideally, a life-cycle assessment (LCA) should be integrated into the building design — carbon hotspots can then be spotted and tackled as they occur. From here, carbon benchmarking has a central role to play in making these substantial reductions in embodied carbon a reality. 

What is carbon benchmarking? 

If the LCA measures emissions, carbon benchmarking gives those measurements context, setting them against a baseline. It’s a way to identify carbon hotspots, track progress, and set realistic targets for reducing emissions. 

“The benchmark helps you understand. Without the benchmark, it would be difficult to make sense of what these numbers mean. In the sense of — ‘Are they good numbers? Are they bad numbers?’ We don’t know that unless we have some sort of benchmark to play around with.”

— Harish Borah, Life Cycle Study Expert, ADW Developments 

Carbon Benchmarking explained: five key takeaways 

Here are 5 points to help you optimize your project’s carbon benchmarking: 

1. All carbon benchmarks need a ‘why’
   

   “Benchmarking for benchmarking’s sake will not work — I think you really have to have a purpose behind it.”
   
   — Harish Borah, Life Cycle Study Expert, ADW Developments

   This purpose could be anything. From evaluating entire buildings, to homing in on distinct features – like façades or substructures. You may need to assess the embodied or operational carbon in certain building types, or you could be tackling whole carbon life cycle assessments across an entire national industry. The goal behind your carbon benchmark is the starting point that defines everything else.

   The Whole Life-Cycle Carbon (WLC) assessment developed by Greater London Authority explains how to calculate Whole Life-Cycle emissions for a building and construction project over its entire life-cycle:

   
   The GLA opted for a 60-year benchmarking period and included all life cycle stages, from construction through to end of life. The benchmark went one step further to include biogenic carbon – which comes from natural products, like timber, and has been included in EU EPDs since 2022.

   
   

   “The GLA basically goes on to include the entire building, because it really wants to capture the entire building industry in the city.”
   
   — Harish Borah, Life Cycle Study Expert, ADW Developments

   
   
2. Much of a building’s carbon emissions occur in its construction 
   
   A building’s embodied carbon describes all the emissions created through its materials and construction processes, throughout the entire lifecycle, including end-of-life. The ratio of embodied carbon to operational carbon (energy used during a building’s day-to-day operations) varies globally. In India, it makes up 40% of total life carbon, according to Architecture 2030. In some regions, it can be 50% or more, and is particularly high in new builds. Factors like transport, machinery, and high carbon materials, like concrete and steel, all contribute — adopting LCAs and carbon benchmarking, empowers project owners to identify buildings’ carbon hotspots and demand higher sustainability standards from manufacturers.
   
   
   

   Carbon benchmarking pinpoints carbon hotspots 

   
   
3. You need to “freeze” your carbon benchmark’s parameters  
   
   

   To “allow an apple-to-apple comparison”, in Harish’s words, the benchmark must stick to key parameters:
   

   • Impact unit – common units include Kilograms of CO2 Equivalent (kg CO2e), Metric Tons of CO2 Equivalent (MT CO2e)
     
     

   • Lifecycle Modules covered:

     • Production Stage A1-A3  
     • Construction Stage A4-A5 
     • Use Stage B1-B7 
     • End-of-Life Stage C1-C4 
     • Beyond Building Life Stage D
       
       
   • Elements to be included – e.g., substructure, superstructure, façades, internal finishes
     
     
   • Study period – this needs to be matched carefully to the lifecycle modules included:
     
     
     • A1 to A5 happens at “year zero”  
     • B4 typically begins around 15 years
     
     
   • Timing: while no benchmark data is ever really “up to date”, construction and manufacturing processes evolve – and datasets go out of date very quickly  
     
     
     • Building type and usage: different building types have varying energy usage
     • A building’s lifespan can vary from under 30 to over 100 years
       
     
     

   • Location: different countries have different energy mixes and manufacturing standards  
     

     “Your carbon benchmark must freeze these parameters — Otherwise, you’ll end up comparing carbons of two designs where one is comparing A and the other one measured B and C as well.”
     
     — Harish Borah, Life Cycle Study Expert, ADW Developments

     
     
4. Carbon benchmarking is not one-size-fits-all 
   
   Carbon benchmarking can be used by private contractors, a municipality, or even a whole country. But to use it effectively, you need to adjust your benchmarking design carefully. Some aspects to consider include: 
   
   
   • Location: different countries have different energy mixes and manufacturing standards  
     
     
   • Timing: while no benchmark data is ever really “up to date”, construction and manufacturing processes evolve – and datasets go out of date very quickly  
     
     
   • Building type and usage: different building types have varying energy usage and lifespans 
   
   
   
   
5. Carbon benchmarking is designed for the big picture 
   

   “What I would hate is if you took one building and did one LCA analysis on it — This number is actually going to be the average for the rest of the country, the city or whatever. Because then, you would have completely missed the point of what a benchmark is!.”
   
   — Harish Borah, Life Cycle Study Expert, ADW Developments
   

   
   When you develop a carbon benchmark for a specific purpose, your goal is to build a broad dataset for a distinct category of building. The more figures are included in that dataset, the more patterns begin to emerge – numbers will often “converge or diverge” – and a big picture will form.   
   

   “You’ve basically entered the realm of statistics from there on — once you’ve done this enough. And then you have complete control to say, ‘I am going to decide, based on this study, all our statistics and everything, that this is what the benchmark should be’.”
   
   — Harish Borah, Life Cycle Study Expert, ADW Developments

How One Click LCA can help you measure embodied carbon 

One Click LCA is the world-leading end-to-end sustainability platform for construction and manufacturing. The software platform decarbonizes and drives sustainability across the construction value chain with scientific, easy-to-use, LCA and environmental product declarations (EPDs) to calculate and reduce the environmental impacts of building, infrastructure, and renovation projects and products. The platform also allows assessment of circularity, life-cycle cost, and biodiversity. One Click LCA is used in 170+ countries, including by blue-chip enterprises like Skanska, WSP, Foster+Partners, LafargeHolcim, ArcelorMittal, Arcadis, ARUP, Geberit, and Saint-Gobain, among others. It offers a unique global database with +250,000 LCA datasets; supports +80 standards and certifications, including LEED, BREEAM, GRESB and other national regulations; and seamlessly integrates with +20 of the most widely used BIM software tools, including Autodesk Revit®, Tekla Structures® and Bentley iTwin®. One Click LCA was founded in Helsinki, Finland in 2001, with a team of +200 people on all continents.