• London Structures Lab

THE CARBON CONUNDRUM



The last year has seen a dramatic shift in policy towards sustainable development. Developers have been requesting embodied carbon studies, with BREEAM 2018 now awarding credits for the tracking of embodied carbon throughout the design stages. Unfortunately, the standards by which these assessments are to be conducted have, for the most part, been badly understood and poorly implemented.

The lack of understanding and poor implementation of assessment standards, combined with the avowed use of natural materials as the only solution, creates an atmosphere of distrust in the sceptics of sustainable development and exasperation for the proponents.

We have the frameworks and information to design sustainable buildings, we just need to start using them.

What is the difference between carbon & sustainability?

Let’s start with carbon and why we are measuring it. Carbon has become the go to terminology for the collection of greenhouse gases (GHG) that have been scientifically proven to cause various forms of climate change through global warming. The scientific community use the term global warming potential (GWP) as the unit of measurement associated with climate change emissions. This is primarily due to the fact that although carbon dioxide (CO2) is the largest source of GHG emissions, other sources like nitrous oxide (N2O) are much more damaging per unit of weight. As a result, the other GHG emissions are factored up so they can be represented alongside the index CO2 emission values. The subsequent GWP unit is quoted in kg.CO2 eq. This is just one very basic example of how the construction industry all too often simplifies concepts to its detriment.

Encouragingly, in November 2017 the Royal Institute of Chartered Surveyors (RICS) published a thorough design note entitled, Whole Life Carbon Assessment for The Built Environment. This makes reference in its background introduction to the poor interpretation of BS EN 15978, the current calculation method for the sustainability of construction, both for new build developments as well as refurbishments.

Unfortunately, a whole life carbon assessment misses a fundamental issue in a development’s sustainability. BS EN 15978, is a Life Cycle Assessment (LCA) that has been developed for application within the construction industry. The following table outlines what are known as environmental impact categories. The table below summarises the main impact categories relevant to the construction industry; GWP (or embodied carbon) is only one of the many other environmental impact categories. These impact categories are the measurable values that, when combined in a specific way, give an assessment of a building’s environmental impact. The critical thing to take away from this tabulated information is that climate change and the associated measurements of GWP are only one part of a full assessment. As designers we need to balance all these issues to ensure the most sustainable solution is realised.

What should we be doing?

Following the recent publication of the RIBA Carbon Challenge 2030, it is clear that there is a consensus in the construction industry to prioritise the measurement of embodied carbon. We assume that the reason for this is largely down to the worldwide reporting of climate change, although it also simplifies the assessments, such that they can become more accessible and therefore applied more widely in practice. Interestingly, the RIBA 2030 challenge is quite open about outlining only a minimum target or standard, with the implication that in time, our assessments will become better and fuller in their scope.

We see a real risk in assessing only the GWP of a building development or refurbishment. There is a potential that through specifying products or materials that appear to have excellently low GWP properties, the designer could be inadvertently damaging other aspects of the environment – so why are building designers not considering this?

Figure 1 - Eutrophication – A dead finish floats in an algae bloom, the outcome of polluting water supplies

Figure 2 - Acidification – A dead forest, the result of migrating acid rain


Figure 3 - Acidification – A dead coral reef, the result of the changing acidity levels in the worlds oceans

Figure 4 - Depletion of Resources – A dried river bed, resulting from overuse of fresh water sources upstream

A lack of sustainability education in the construction industry is certainly one reason. However, until recently obtaining environmental impact information for products, materials and processes was very difficult. Most embodied carbon assessments use databases such as the Inventory of Carbon & Energy database (ICE). Although this is an excellent resource for embodied carbon and energy values associated with the production of construction materials, it has no information regarding the other environmental impact categories. It also does not contain many composite products or proprietary products that are regular used and often offer significant efficiencies. Where can we get all this information from and how can we make sure that it is accurate?

Environmental Product Declarations

In 2012, the European Committee for Standardisation published EN 15804. This standard outlines Product Category Rules (PCR) for the production of Environmental Product Declarations (EPD) specific to the construction sector.

This standard essentially sets out how companies within the sector complete LCAs for their products. The outcome of this is that each of their products can have a certificate with measurable information for each of the environmental impact categories. As designers, we can then take these EPD certificates and use them along with the material quantities of our designs to establish like-for-like comparisons.

References such as the BRE Global GreenBookLive manage vast numbers of EPDs from different companies, allowing for a simple and easily searchable database of EPD certificates. It is even more common now that large companies such as TATA Steel offer bespoke EPD certificates for their products based on location and other relevant factors.

The EN 15804 EPD standards require a robust consideration of the LCA boundaries and provide the designer and client with realistic assumptions for how the materials will be treated throughout their lifetime, including aspects of reuse and recycling.

The use of EPDs and the full suite of environmental impact information they contain will provide designers with much more information on which to base their decisions. We will be able to interrogate the EPDs and have more certainty in comparing them.

However, one of the final challenges, is related to the assessment of the environmental impact values associated with the construction stages of the building lifecycle process. Referred to in the standard as stage A4 and A5, these impacts are associated with the transportation of materials from the factory and the processes associated with their assembly onsite. The environmental impacts associated with these should not be ignored as they can be significant and will be different for each project and proposed structural option.

Figures 5&6 - The environmental impacts generated during the construction stages of a project are significant. The waste and emission from different types of on-site and off-site construction need to be considered to have an informed debate about materiality in the early concept stages.

It can be argued that this portion of the assessment needs to fall into the hands of the principle contractor. There is scope for the client to give tendering contractors environmental performance targets to hit in the transportation, erection, deconstruction and reuse of buildings; creating a new element of competition other than the race to the bottom on cost. Contractors that invest in clean vehicles, control material wastage and set up sustainable supply chains will win in the long term. A number of forward thinking contractors are doing this already, and the next step is publishing an audited EPD-like certificate for different forms of construction. This would allow them to compare their average environmental impact for digging basements in a city centre, with building a steel portal frame in the countryside. This would be an invaluable source of information and would allow designers to put equivalent units to volumes or areas in their initial design concepts.

Considering the whole, not just the parts

During the writing of this article we considered many different structural concepts and the methods by which they could be environmentally assessed. During this process one theme continued to arise. In nearly every example we considered, the individual characteristics of each structural concept would have direct impacts on other aspects of both architectural and operational energy specification. We believe that when one discipline attempts to review their concept in isolation to another there is scope for the impact of design decisions to be underestimated.

For example, the specification of a steel frame structure will require fire protection of some kind. If this is a painted system should we assume that the architect will consider the environmental impacts of this, including its lifecycle maintenance requirements? Or should we take this into account when comparing the steel framed option with a reinforced concrete option, which has an inherent fire protection? These kinds of consideration are dependant on many design variables and need to be carefully coordinated by the designers to ensure the environmental performance of each option can be effectively compared.


Figure 7 - There are many processes, treatments and finishes that are applied to construction materials after they leave the factory. In this image a construction worker is sand blasting steelwork on-site, preparing it for a painted finish.

As designers within a team, we are used to producing information for costing at every stage. We need to educate ourselves and become able to produce similar models for the assessment of sustainability. Much like a cost model these models are rough big picture figures in the early stages and are sharpened as the design progresses. Without this assessment in place we can’t benchmark and will never be able to hold ourselves accountable when we “overspend”.

Far more needs to be done, if as an industry we are to obtain a better understanding of the environmental performance of our designs. In many ways, the million dollar question is not whether we can complete these assessments properly, but whether the design process, as it traditionally exists, is set up to achieve our targets. We can’t be sure how the industry will resolve all the issues, but we do know that all parties need to increase their knowledge in a common curriculum and above all must communicate openly and inclusively.