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.
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)
||68% reductrion on 1990 by 2030
||Net zero by 2050
||52% reduction on 2005 by 2030
||Net zero by 2050
||65% reduction on 2005 by 2030
||Net zero by 2060
||45% reduction on 2005 by 2030
||Net zero by 2070
||43% reduction on 2005 by 2030
||Net zero by 2050
||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.
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 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.
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.
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.
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.
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.
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.
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.
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.