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  • Michael McCarthy

What is the fastest way to reduce a country’s carbon emissions?

We have seven years to reduce our carbon emissions by half. That’s right, seven. It is eight years since the Paris climate agreement to hold average global warming temperature increases (above pre-industrial levels) below the critical 1.5 degrees limit. With emissions still rising, we are currently at 1.25 degrees and the concentration of CO2 in the atmosphere just breached 425ppm for the first time in human existence. It is a really bleak scenario.

Decarbonising the grid and transportation takes time and massive investment, as will be insulating our housing stock. Decarbonising agriculture will also be expensive and politically fraught.

However, decarbonising construction can happen quickly, at little or no extra cost, and the effects are immediate.

Construction of buildings accounts for 14% of CO2 emissions in Ireland, or about 8.7m tonnes. Most of this (70-80%) is in the production of materials, predominantly concrete and metals, so reductions in carbon here occur on day one of a project, whereas operational carbon savings happen over 50 years.

The remaining 20% is comprised of transportation to and from site (2%), the construction process itself (1-2%), replacement and maintenance during a 50-year period (15%) and demolition (1-2%).

As energy efficiency of buildings improve and the carbon intensity of the grid decreases, embodied carbon of buildings will become the main source of emissions, as demonstrated by this graphic from LETI (London Energy Transition Initiative).

Life Cycle Assessment

The process for calculating emissions from the construction and maintenance of buildings is known as Life Cycle Assessment (LCA). In order to guarantee the validity of the process, it is rigorous and detailed.

European standard EN 15978 specifies this LCA calculation and reporting process, providing indicators, calculation rules and system boundaries for the assessment.

In practical terms, aspects of the EN 15978 methodology have been subject to varying interpretations by practitioners and clients: different scopes commissioned according to different client requirements, varying assumptions made and poor-quality data selectively and/ or inappropriately used. It has therefore become apparent that a harmonised approach to the practical application of the standard has been lacking.

RICS guidance ‘Whole life carbon assessment for the built environment’

One such harmonised approach is the EU Level(s) framework.

Level(s) is an EU initiative that provides a common framework for assessing and reporting on the sustainability performance of buildings, across six core sustainability indicators which measure carbon, materials, water, health, comfort, and climate change impacts throughout a building’s full life cycle.

Indicators of particular interest to us are Indicators 1 and 6, which measure a building’s Life Cycle Assessment (LCA) and Life Cycle Cost (LCC).

The EU Level(s) framework is a holistic and integrated approach that weaves all sustainable elements together for lower carbon, higher circularity, lower lifetime costs and all round healthier buildings.

The process of undertaking an LCA is however currently a very laborious and resource intensive.

By far the best, and in our view, the only software for doing LCAs is One Click LCA. This platform that provides the certainty that is required to give confidence in the process.

Currently, extracting quantities from bills of quantities, converting them into a usable LCA unit (e.g. volume or weight), then matching those materials to an appropriate Environmental Product Declaration (EPD) is a very time consuming process.

Completing LCAs as an add-on to the current procurement process will not work for mass adoption of LCAs.

What is required is to consider LCAs as a fundamental part of the design process from inception. This means targeting a total embodied carbon reduction from the outset and then developing the design stages to reflect this target.

This will be an entirely new specialism that combines cost management and life cycle costing to be integrated with LCA. It will also be an entirely new way of working for design teams as carbon will have as much impact on the design as cost.

What are the targets and how do we get there?

The LETI targets are the most ambitious in the industry. They aim to reduce embodied carbon by 65%. This is a tall, but necessary, order and one that will not be possible without some fundamental changes to building regulations, planning legislation and agricultural policies.

The initial task is establishing the baseline typologies by which to measure carbon reductions. This is a process that is being undertaken by the IGBC who are working to establish baselines for a number of archetypes.

Another short coming is the lack of EPDs for Irish construction products. To counteract this, the IGBC are developing a database of typical carbon intensities for products in the Irish market. This will help to streamline LCAs and ensure that appropriate carbon intensities are used in calculating LCAs.

Reducing Irish construction embodied carbon by 65% would be to reduce emissions by 5.5m tonnes per year. This is half the entire emissions for the transport sector in 2021.

It will be the job of the design team, and in particular the quantity surveyor to manage the carbon and cost budgets in tandem throughout the design process.

At the early stages of a design, this can be achieved with One Click’s Carbon Designer tool. Different construction typologies can be tested quickly and efficiently in tandem with different iterations of the projects cost plan.

But LCA’s and clever design will only go so far. One of the biggest impediments to low carbon buildings are the building regulations. In particular, a very stringent and onerous Part B (Fire). Not just are the regulations highly restrictive, they can be interpreted even more severely by local fire officers.

For example, in Cork, it is not possible to build the upper unit of a duplex in timber frame, where it is possible in Kildare and Dublin due to different fire officer interpretations of the regulations.

Our building regulations follow the UK’s closely, however, 6 stories of apartments are permitted in timber frame there, where apartments in timber frame are not allowed here.

Building regulations also need to address construction in Cross Laminated Timber (CLT) and other biogenic materials if we are to be serious about reducing emissions and meeting our climate targets.

The next issue is the widespread adoption of LCAs. This can only be achieved if it is mandated. The best place to do this is in planning legislation. In Denmark, all projects over 1,000m2 must submit an LCA calculation complying to phased targets. From the end of 2023, it will apply to all buildings seeking planning approval. It also has more ambitious parallel voluntary targets.


  • Completing LCAs as a straight add-on to the current design process is inefficient and will not work for mass adoption.

  • The whole design process needs to be revised to incorporate EU Level(s) including LCA and LCC.

  • Intensive early-stage options to work out the optimal carbon / cost solution is critical.

  • Aim for maximum reductions in embodied carbon – it is the cheapest and most immediate and effective carbon reductions available.

  • Primary legislation is needed to effect industry wide adoption.

  • Building regulations need to be changed to allow more bio-genic materials, in particular timber frame and mass timber buildings.

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