International drivers of low carbon structural design

Author: Tom Harley-Tuffs and Jonathan Russell

Date published

3 April 2023

Price
Free
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International drivers of low carbon structural design

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Author
Date published
Price
Guidance
Author

Tom Harley-Tuffs and Jonathan Russell

Date published

3 April 2023

Author

Tom Harley-Tuffs and Jonathan Russell

Price

Free

Tom Harley-Tuffs and Jonathan Russell from the Sustainability Panel explore how government legislation and investor commitments are causing clients globally to put carbon first.

Synopsis

Environmental certification schemes have historically required carbon assessment on projects, but their effectiveness as a tool for promoting low carbon design is often limited. The world’s major economies have established legislation in an effort to achieve net zero greenhouse gas emissions and combat climate change. To meet these commitments, national governments are regulating carbon emissions in the construction industry, with some regulations in place or in the pipeline. Investors are prioritizing low carbon projects, and developers and building operators are aligning their business models with these goals, including requirements for embodied carbon in their sustainability briefs.

In the coming decade, structural engineers have the opportunity to lead the way in this transition towards a low-carbon built environment, but immediate action is needed to measure and reduce carbon on a project level before regulations catch up. In this article we highlight international best practice examples of drivers for low carbon design. Sharing knowledge and best practice across borders allows us to develop and innovate in step at an international level.
 

Certification schemes

Historically, environmental certification schemes have been the main driver of using life cycle assessment (LCA) to quantify embodied carbon emissions associated with buildings. They can therefore in theory be a driver for implementation of low carbon design on projects. Most environmental certification schemes require some form of life cycle assessment to be undertaken (Jensen & Birgisdottir, 2018). While not mandatory, achieving the highest levels of certification is challenging without LCA. Local planning authorities may mandate certification (BRE, 2021) and institution or publicly funded projects often have minimum compliance levels. However, the adoption of certification across construction internationally varies widely.

One of the most critical decisions a structural engineer can support a client and design team in making is whether a new building is required at all. The hierarchy of ’build nothing > build less > build clever’ strongly encourages a “refurbish first” approach. Many of the most common environmental certification schemes only award from concept design onwards, by which point this crucial choice has already been made, and the substantial benefits of the choice are not recognised.

In the UK BREEAM NC 2018 awards a significant number (~7%) of materials credits for integration of Life Cycle Assessment methodologies at concept design and technical design stages (BRE, 2018). Credits are awarded based on design option studies being undertaken and the environmental impact of each studied during the relevant design stages. However, the scheme does not require specific targets to be met or even that the lowest carbon option is selected. The accuracy and rigour necessary for a whole building study also makes it time consuming to carry out, and the LCA results often ‘lag behind’ the current considerations of the design team by weeks. It is debateable therefore how much the certification in its current form influences design decisions and leads to low carbon outcomes.

LEED BD+C v4.1 is widely used in the US and Canada. It goes somewhat further than BREEAM, with the materials credit requiring LCA studies across a wide variety of indicators and not only global warming potential (US Green Building Council, 2018). It also awards credits based on a demonstrable reduction of impact from the design process through to construction on site. A 20% reduction in carbon, 10% reduction in other impact categories, and re-use or salvaged materials gives the maximum score. Anecdotally many clients consider ‘cost per credit’ when achieving a certain level of accreditation, meaning that this credit is often not pursued.

Singapore's Green Mark is a voluntary certification scheme with credits awarded to a variety of sustainable buildings categories (Building and Construction Authority, 2021). For the whole life carbon credit CN1 the 2021 edition awards credits for undertaking whole life carbon assessment of the project. Unlike most other certification schemes, it sets maximum embodied carbon rates (A1-A4) for the superstructure, ranging from 1000-2500 kgCO2e/m2 depending on building usage. Further credits are awarded for buildings that achieve 10% and 30% below these rates. The relatively high carbon targets compared to European legislation (refer to part 2) are reflective of Singapore's unique construction constraints. Limited land and prevalence of concrete in construction result in high rise, high carbon buildings.

The DGNB system is widely used in Germany and Denmark, and puts equal weighting on social, economic and environmental factors in its evaluation (DGNB, 2020). Credit ENV1.1 awards points for undertaking life cycle assessment during the design process, using it for building optimisation, and for buildings that beat specific targets (9.4 kgCO2e/m2/yr, 470 kgCO2e/m2 over 50yrs). The highest grade is awarded to buildings that achieve a >45% reduction on these target values. It also covers other indicators beside global warming potential, although GWP is still given the most weighting. In principle this therefore incentivises ‘good’ low carbon design.

In conclusion, environmental certification schemes can be a useful tool for encouraging low carbon design in the construction industry, but their effectiveness varies. Many schemes only award credits from the concept design stage onwards, meaning that the decision to refurbish an existing building rather than construct a new one is not recognized. In addition, certification schemes require an informed client willing to pursue certification. Consequently, certification schemes on their own do not appear to be a major driver for low carbon design as they only target a small subset of the construction industry, and overlook decisions made when establishing a project brief.

Challenges in comparing countries and schemes

Certification methods and assessment standards vary significantly between countries, making side by side comparison of carbon impacts for construction in different countries difficult.

The majority of schemes require appraising the superstructure and substructure as a minimum. The minimum required scope of life cycle stages vary significantly (Figure 1) (Ramboll, 2022). Structural engineers have the most influence over upfront emissions (A1-A5), end of life (C1-C4) and circularity (D). Whilst the product stage (A1-A3) is usually mandatory, transport (A4) and installation (A5) are sometimes optional or specifically excluded, leading to distorted results when considering products with relatively high transport emissions, such as mass timber or other implementations of modern methods of construction (MMC). End of Life (C1-C4) is often optional or excluded, and Circularity (D) even less widely accounted for, potentially leading to inappropriate use of materials like concrete that cannot readily be re-used.

The outcome of this is that if one country tends to report lower impacts than another it is hard to know whether this is as a result of low carbon materials, different construction approaches, or simply a different way of measuring. Without a suitably robust methodology to ‘fill in the gaps’ between different scopes of LCA it is challenging to identify the most effective variables in creating low carbon buildings.
 

Country commitments

Several countries have established legislation in an effort to achieve net zero greenhouse gas emissions and combat climate change. The UK, European Union, United States, China, India, and Australia have all made commitments to reduce or eliminate emissions. As structural engineers, the work of organisations such as the IStructE may be somewhat detached from the politics and national level commitments to combat climate change; however, the commitments demonstrate the importance of the issue at a global level. The important question for structural engineers is how will these commitments be implemented in practice?
 

Table 1: National commitments of major economies to carbon reduction (Climate Action Tracker, 2023)
Country Short-term commitment Long-term committment
UK 68% reductrion on 1990 by 2030 Net zero by 2050
USA 52% reduction on 2005 by 2030 Net zero by 2050
China 65% reduction on 2005 by 2030 Net zero by 2060
India 45% reduction on 2005 by 2030 Net zero by 2070
Australia 43% reduction on 2005 by 2030 Net zero by 2050
Japan 46% reduction on 2013 by 2030 Net zero by 2050

 

Embodied carbon regulations

To achieve the targets described in the various country national climate commitments, governments in these nations will look to top-down regulation of carbon emissions in construction. Some nations have already implemented regulation, many others are waiting to follow suit. These regulations vary in scope, metric, and magnitude of required year-on-year reductions. Most nations will have a unique implementation, as there is no clear consensus on how to regulate in regards to LCA scope and preferred metric.

For structural engineers operating internationally, it is important to have a basic understanding of the implications of the regulations. A short list is provided here, giving an overview of nations with either active or incipient regulations.

Denmark
The LCA ecosystem in Denmark grew out of the German DGNB certification scheme, which assesses environmental impacts on a whole-life carbon basis (LCA stages A-D) and in the unit kgCO2/m2/yr. A carbon emission limit value of 12 kgCO2/m2/yr will be enacted starting January 2023 for buildings over 1,000m2. With a reference period of 50 years, this amounts to 600 kgCO2/m2. This limit value is scheduled to reduce by 1.5 kgCO2/m2/yr every two years, reaching 7.5 kgCO2/m2/yr in 2029, and will apply to all buildings from 2025.

The Netherlands
The Dutch Building Decree states that all office buildings over 100m2 and all residential buildings must adhere to the Milieu Prestatie Berekening (MPG). The MPG is based on a whole-life LCA, according to the European EN 15804 + A2 standard, but converts environmental impact values (e.g. global warming potential, ozone layer depletion, ocean acidification etc.) into a shadow price (e.g. €0,05/kgCO2eq, €30/kgCFC-11 eq, and €4/kgSO4eq). The combined shadow price of the project per floor area then is subject to a limit of 1,0 €/m2/yr, which for residential buildings was tightened to 0,8 €/m2/yr in 2021, and is proposed to be reduced to 0,5 €/m2/yr in 2030. The Dutch methodology thus looks beyond just carbon emissions in regulating the environmental impact of buildings.

France
The RE2020 regulation was instituted in early 2022, in which limit values for whole life embodied and operational carbon emissions are set. For single family homes, whole-life embodied carbon values are set at 640 kgCO2e/m2 for 2022, reducing every three years to 415 kgCO2e/m2 by 2031. The values for offices are higher, starting at 980 kgCO2e/m2. The regulation also enacts a ‘dynamic carbon calculation’, adding a factor to reflect the greater impact of current over future emissions.

UK
No current national limit values. Building Regulations Part Z proposals introduces a mandatory LCA from 2023 and (as of yet undefined) carbon limits are proposed for 2027. The Greater London Authority now requires whole life carbon assessment and circular economy statements before planning applications are granted. Other local authorities sometimes mandate BREEAM certification, and this has credits related to carbon reduction as discussed in part 2.

Sweden
The Swedish National Board of Housing, Building and Planning (Boverket), enacted a ‘Regulation on Climate Declarations for Buildings’ on January 1st 2022, stipulating that all projects requiring a building permit must provide a climate declaration, which describes the building’s climate impact, calculated on the basis of greenhouse gas emissions from the construction stage (A1-A5). Limit values are being developed and are expected latest by 2027. Currently, limit values are described as increasing percentage reductions with respect to an as-of-yet undefined reference value.

Norway
The Norwegian Building Regulations were expaned on 1 July 2022 with chapters on energy and greenhouse gas emissions. These are active on a voluntary basis for a year, after which they become mandatory. The regulations relate to apartment blocks and commercial buildings, and the required greenhouse gas calculation shall be according to the Norwegian NS 3720:2018 methodology. Although the methodology encompasses the whole life cycle of a building, the regulation will cover only upfront carbon (A1-A4) and replacements (B4). The results are expressed in kgCO2/m2/yr and the assessment period is 60 years.

Finland
In late 2022, the Finnish government approved a proposal to amend the Building Act. The amendments would describe the technical requirements regarding carbon considerations for new projects, and would be authorised to issue carbon footprint limits. Project values would be expressed in kgCO2/m2/yr. The regulations are expected to enter the Finnish Building Code in January 2024.

USA
While there is no national legislation on carbon regulations, the State of California and the State of New York – together comprising 60 million people – both enacted legislation in 2022 which mandate LCA for certain buildings, AB-2446 (California Legislative Information, 2022) and Executive Order 22 (Hochul, 2022) respectively. These buildings include new residential buildings with five or more units or non-residential buildings larger than 10,000 square feet (930m2) in California, or all state agencies development in New York.

China
In 2021, GB55015-2021 was enacted, which requires a 40% reduction in carbon emissions with reference to the standard reference building from GB50189-2015 (Design Standard for Energy Efficiency of Public Buildings).
 

Comparing regulatory targets

The graph below shows whole life carbon emissions regulation values and estimated regulation values for the countries described above. Additionally, target values from SCORS, LETI, and RIBA are included, as these are commonly used as benchmarks in the UK construction industry. The unit for comparison is kgCO2e/m2 and the graph considers upfront structural carbon only (life cycle modules A1-A5 as per EN 15978, superstructure and substructure only).

The result is a rough attempt at a harmonized comparison of active European carbon emission limits. The exact numbers are unlikely to be correct, as they are estimated using conversion factors between LCA scope boundaries (derived from  (LETI, 2020)), but they still give engineers an indication of the ambition level required across the continent. Different sources suggest various factors for converting between values for WLC (A-C) and upfront carbon (A1-A5), and between upfront carbon (A1-A5) and structural upfront carbon (A1-A5), and values are often differentiated depending on building typology. The conversion factors assumed for this study come from RICS guidance, values which also were used as the basis for the SCORS rating scheme. Reference values are provided as a footnote.

Relatively few nations have active limits. While we wait for standards to arrive, engineers may find security in the fact that if they adhere to the SCORS ratings from 2030 onwards, they are likely on the correct side of any new regulations to emerge.

However, the SCORS pathway represents an industry average, so climate-aware engineers should aim well below these values, setting best practice precedents to demonstrate their viability and encouraging adoption as the new ‘business as usual’ in a few years. This approach also makes up for colleagues who are less informed or less able to achieve such designs. This heightened ambition level would also comfortably situate complying projects on the safe side of all existing European carbon regulations and could therefore be termed a ‘European best practice’ level. An estimation of this benchmark is represented by the green dashed line in the graph.

Investor and developer influence

Investors are being driven to prioritize low carbon projects due to EU legislation like the Sustainable Finance Disclosure Regulation and EU Taxonomy, as well as government regulation such as the Task Force on Climate-Related Financial Disclosures and upcoming transition plans. These regulatory factors, along with consumer interest and pressure, are increasing the mandatory aspect of low carbon investments and creating a permanent focus on sustainability.

In addition, the availability of data and comparison through certifications is driving investors to act in order to maintain a strong industry reputation. Standardisation of data and certifications, as well as the maturity of technology, is also making low carbon projects more accessible. The upcoming Net Zero Carbon Buildings Standard (UKGBC, 2023) will be a valuable data source in coming years. These projects can also offer parallel benefits such as efficiency gains, an engaged workforce, and social value. Significantly, annual reporting and positive news stories are essential for maintaining investor interest in low carbon projects.

As a result, investors are looking for developments meeting environmental social governance targets and aligned with their policies and aspirations. Developers and building operators are therefore incentivised to re-align their business models with these goals, and many major developers now have bespoke holistic sustainability briefs. These often include key performance indicators (KPIs) for embodied carbon.

In the author’s experience it is these forward-thinking clients and their low carbon aspirations that are pushing structural engineers and design teams most directly to adopt new approaches and solutions to their projects. The goal of national carbon regulations is to help less forward-thinking clients develop low carbon aspirations.

Investors and developers are uniquely positioned to connect the social, economical and environmental strings of a project. The structural engineer can bring solutions that address all of these aspects and drive the brief by demonstrating that there are new unconsidered options available. This goes beyond the traditional remit of the structural engineer, with clients increasingly expecting them to be bold and bring new solutions to the table.
 

A key role for structural engineers

Many nations have committed to net zero carbon in the next 30 years. Legislation in the built environment is coming, with many countries setting embodied carbon targets that come into force this decade. The structural engineer sits at the centre of identifying the pit falls, embedding best practice as business as usual, and driving change through innovation. This is not a new role for the structural engineer!

While these drivers are coming, they have yet to make a significant difference on the day-to-day work of the structural engineer; business as usual still passes for now. Life cycle assessment as currently implemented through certification schemes lags behind real time design decision making, and so it falls to designers to incorporate simplified carbon and circularity assessment into their day-to-day design processes. Real change today comes when informed clients and design teams choose to put climate first, rethinking tried and tested approaches and viewing them through the new lens of carbon reduction. Soon all development will be pushed down this path, but in the short term the significant change we need is coming from the bottom up. Understanding local requirements, self regulating design impacts and sharing knowledge and best practice across borders will enable engineers to improve and innovate in step.

As structural engineers we have a duty to our clients and to global society to be aware of these forthcoming challenges, acting now to guide our projects on the right path. This decade may see the most radical shift in the built environment in a generation. Structural engineers across the world have the opportunity to lead the way and be that driving force for change.
 

References

BRE, 2018. BREEAM New Construction 2018 (UK) Manual

BRE, 2021. Policy Landscape - England

Building and Construction Authority, 2021. Green Mark

California Legislative Information, 2022. AB-2446 Embodied carbon emissions: construction materials

Climate Action Tracker, 2023. Countries

DGNB, 2020. ENV1.1 Building life cycle assessment

Hochul, K., 2022. No. 22: Leading by Example: Directing State Agencies to Adopt a Sustainability and Decarbonization Program

Jensen, K. G. & Birgisdottir, H., 2018. Guide to Sustainable Building Certifications

LETI, 2020. Embodied Carbon Primer

Ramboll, 2022. The carbon footprint of buildings

UKGBC, 2023. UK Net Zero Carbon Buildings Standard

US Green Building Council, 2018. LEED v4.1.

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