Image: Some of the opportunities to minimize embodied carbon
from feasibility through to material specification. Click to enlarge.
“What can I, a designer, do to reduce
Embodied Carbon (ECO2e)?”
published July 2019 by Andrew Minson,
Director Concrete and Sustainable Construction-GCCA
-Global Cement and Concrete Association-Guildford, United Kingdom:
Sustainability is complex: “Leadership in Energy and Environmental Design (LEED) and Building Research Establishment Environmental Assessment Methodology (BREEAM), the two most common building assessment methods have 9 and 10 main categories respectively. Given this complexity our industry messages on embodied carbon have, perhaps understandably, not always been clear”—at least that was what Minson was told directly by a designer. So, responding to the challenge, he developed guidelines to reducing embodied carbon:
Significant lifetime ECO2e is associated with floor, wall and ceiling finishes specified by the architect for aesthetic reasons or for the purpose of fire protection. Can these be minimised or avoided? Exposed visual concrete is certainly back in trend with architects and therefore does not need replacing on 10-15-year cycles. (Please see the Mineral Products Association (MPA) ‘The Concrete Center’ Material Efficiency page: https://www.concretecentre.com/Performance-Sustainability-(1)/Material-Effieciency.aspx)
There is also significant ECO2e associated with plant and equipment specified by services engineers, and once again this needs maintenance and replacing throughout the asset lifetime. Explore if cooling and heating requirements can be minimised, and hence plant and ducting reduced or avoided, by utilising concrete’s thermal mass. (Please see the MPA ‘The Concrete Center’ Thermal Mass page: https://www.concretecentre.com/Performance-Sustainability-(1)/Thermal-Mass.aspx).
Building facades are key to addressing building energy performance and this can drive their specification, but they are another significant contributor to ECO2e and are specified by the architect or specialist facade designer, and are replaced during the asset’s lifetime. Concrete masonry and precast façade solutions offer alternatives that have long lasting benefits. And if the overall floor build up (underside of ceiling to top of floor covering) can be minimised then total façade area is reduced.
The structural engineer specifies structure and substructure. Some LCA studies point to this as being the largest contributor to ECO2e but beware, as it is likely that one or more of finishes, services, and facades have been omitted. The structural engineer can minimise ECO2e by harnessing its design versatility and choosing the optimum concrete design solution. For concrete floors alone, there are 13 options. (Please see the MPA ‘The Concrete Center’ Concept Design Tool – Version 3 page: https://www.concretecentre.com/Publications-Software/Publications/Concept-Design-Tool-Version-3.aspx)
At more detailed design stages, structural engineers can sharpen their pencil on their design as well as optimise concrete strength, reinforcement percentage and section size to minimise embodied carbon. And there are also significant gains, because of mix versatility to be made in specification of concrete. Please see table below:
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WHAT ENGINEERS CAN DO WHEN SPECIFYING CONCRETE?
Source: “Specifying Sustainable Concrete” The Concrete Centre
1 Do not over-specify strength
2 Consider the possibility of strength conformity at 56 days rather than the conventional 28 days
3 Specify responsibly-sourced concrete and reinforcement
4 Do not specify maximum aggregate sizes below 10mm unless necessary
5 Permit the use of recycled or secondary aggregates but do not over specify
6 Specify that concrete should contain secondary/replacement cementitious (e.g. fly ash, ggbs)
7 Permit the use of admixtures
8 ECO2e of concrete should not be considered or specified in isolation of other factors such as strength gain, strength and durability
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Designers alongside the client should consider whole life resilience to reduce lifetime ECO2e. Work at MIT has investigated whole life cost savings from resilient design:
MIT Concrete Sustainability Hub (CSH) “Resilience” page:
“In hazard-prone areas, hazard-induced maintenance costs can be significant over the lifetime of a building. In fact, the costs of hazard-related repairs can exceed the initial building cost. Our team has developed a building life cycle cost analysis (LCCA) approach that incorporates operational costs associated with energy consumption and repairs due to damage from hazards. Our case studies have demonstrated that investing in more hazard-resistant residential construction in certain locations is very cost-effective.”:
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In this case, cost has direct parallels to lifetime ECO2e. Also designers should consider resilience to overheating through application of thermal mass—retrofit of air-conditioning, even with a decarbonised grid, is an adverse outcome. Please go to MIT CSH page: https://cshub.mit.edu/buildings/resilience
To quantify ECO2e there are standards in place for Life Cycle Analysis (LCA) and Environmental Product Decclarations (EPD). The concrete sector has embraced these and cement and concrete EPDs are available. The Global Cement and Concrete Association (GCCA) EPD tool enables concrete manufacturers to provide industry consistent EPD’s into the market. Concrete EPDs are useful when optimising concrete solutions, but comparison between construction materials is “fraught with complexity” according to the IISD which states:
“Building professionals looking to decarbonise buildings should exercise caution when making decision that prefer one building material over another. Uncertainties, assumptions and omissions in LCA studies, particularly with respect to biogenic carbon emission of wood products, suggest that comparisons across building materials are fraught with complexity.” —International Institute for Sustainable Development, “Emission Omissions”, April 2019. For the GCCA EPD tool on the GCCA “Environmental Product Declarations” page, please go to: https://gccassociation.org/sustainability-innovation/environmental-product-declarations/
For GCCA Website, please go to: https://gccassociation.org
A final thought is that reductions in embodied carbon are possible from some fundamental client choices. Is the floor loading in the client’s brief unnecessarily high? If it is, it results in unnecessary structure and embodied carbon. And even more fundamental questions for the client are; is refurbishment of an existing asset a better choice? and, can the need for space be avoided altogether? These questions can be guided by designers.
There is a lot that designers can do, and the concrete industry
is helping to enable and equip them.
For the entire article, please go to: https://www.linkedin.com/pulse/what-can-i-designer-do-reduce-embodied-carbon-eco2e-andrew-minson/
To download the PDF of the article titled “An Analysis of the Most Adopted Rating Systems for Assessing the Environmental Impact of Buildings”, please go to: sustainability-09-01226 (https://www.concretepavements.org/wp-content/uploads/2019/08/sustainability-09-01226.pdf)
Lori Tiefenthaler, Sr. Director of Marketing-Lehigh Hanson, recently shared this article titled “What can I, a designer, do to reduce Embodied Carbon (ECO2e)?” published July 2019 by Andrew Minson, Director Concrete and Sustainable Construction-GCCA-Global Cement and Concrete Association-Guildford, United Kingdom. Lori remarked “Great Article on Lower Carbon Concrete!”