Since February, ACAN has been calling on the UK Government to introduce Building Regulations to require all new buildings to calculate and report whole life-cycle carbon emissions, writes Joe Giddings. We didn’t pluck this request from thin air. We looked abroad to see how other countries are aiming to reduce emissions arising from construction.
The most relevant example was just over the channel, where France is pressing ahead with a new policy that will result in all new buildings built in 2031 having a 52% reduction in embodied carbon emissions over today’s standard. In this long read, structural engineer Frédéric Bourgeon explains how the new regulations work, illustrated with a beautiful residential scheme by MARS Architectes in Paris.
Firstly in November 2020, and then in more detail in February 2021, French Minister of Ecological Transition Barbara Pompili and Minister Delegate for Housing Emmanuelle Wargon announced the guiding principles for the future environmental regulations, ‘RE2020’, to be applicable to new build developments starting in 2022. RE2020 will be the seventh major set of regulations on energy use within buildings in France, the first of which was created in 1974. But this newest iteration will pack in a major addition: carbon, both operational and embodied, is now part of the picture.
Since 2016, France has been testing possible new regulations on actual buildings through the E+C- (Positive energy, carbon reduction) experiment. This four-year period has been a shared opportunity for both project teams and regulators. The former could benefit from construction bonuses, enticing developers to take part by allowing up to +30% built area per plot to balance efforts in meeting a set of ecological criteria, with an innovative certification offered upon approval of reaching a set performance level. Whilst the regulators gathered valuable real-life data and feedback to inform coherent regulations in line with the roadmap set out in the low-carbon strategy “Stratégie Bas Carbone”. The strategy sets the following aims:
Halving carbon emissions related to the building sector by 2030 in comparison to 2015
A fully decarbonised building sector by 2050
The new regulation details are expected to be published this month for new build individual and multi-dwelling housing and will be applicable starting January 1st 2022. Details regarding other typologies (retail, offices, hospitals, etc.) will be worked out during 2021 and are expected to be applicable sometime during 2022.
And while RE2020 will set the baseline, a state-supported label will recognise projects which demonstrate further innovation and can be used as best-in-class examples paving the way towards the collective climate objectives.
Getting up to speed
RE2020 builds on the previous regulation, RT2012 which only covered energy in-use requirements, and introduces new objectives that are required for a project to receive planning permission. The upcoming regulation sets various indicators pertaining to three categories : energy use, carbon emissions and summer comfort.
At the moment of writing, two independent indicators have been designed regarding carbon emissions, one on the emissions related to energy use and one to those from building materials. Both indicators will be progressively lowered to allow for upskilling of the industry. The proposed timing is intentionally challenging as the issues are pressing and the objectives of the SNBC call for prompt reduction of carbon emissions:
2022 : the new regulation is applicable to all new housing projects
2025 : the thresholds are reduced ~15% in comparison to 2022
2027 : the thresholds are reduced ~10% in comparison to 2025
2031 : thresholds further reduced ~15% in comparison to 2027
Overall, in 2031, the carbon emission thresholds will be reduced by an average of 52% in comparison to 2022.
Innovation & then some more: Dynamic Life-Cycle Analysis
Introducing carbon emission indicators and thresholds puts France among the short list of countries enforcing a more global and cohesive set of building regulations. But, to our knowledge, France is the only country to have selected a dynamic life-cycle approach to calculate the carbon-related indicators.
Dynamic life-cycle analysis is not new and is based on a simple idea: the time factor of carbon emissions alters the impact they will have on our climate. Within this dynamic approach, carbon emissions that are caused now will have a greater impact bearing than the emissions that are 60 years down the line. After all, we live in a climate emergency, acting NOW is better than acting in 50 or 60 years.
The infrastructure
France builds on the INIES database, which is free to access, which gathers lifecycle data from manufacturers and default data spanning all phases of a project (A-D lifecycle analysis). This database contains more than 2,000 data entries for construction products and around 450 for building equipment from luminaries to chillers and solar panels. All of this data is said to represent a whopping 640,000 commercial Products.
It is interesting to note that while RE2020 uses only equivalent CO2 figures from the INIES database, manufacturers report many other values that can further inform the design such as freshwater usage or eutrophication potential. Some of these can be used as a measure for the building potential for circular economy or its impact on biodiversity.
As previously mentioned, embodied carbon maximums are set within the regulation. These threshold values are varied based on several criteria such as the amount of default data (i.e not project specific) within the lifecycle analysis and even factors such as the area occupied by underground parking. Variations will also evolve in time in order to incentivise industries to evaluate and document the embodied carbon of their product line.
For instance, in the current proposal the embodied carbon threshold is set so that the infrastructure section of the calculation will be capped to a maximum of 40 kgCO2/m² if underground parking is required due to local planning requirements.
The base threshold values, including the construction phase, are the following:
But the new regulation does not stop at regulating embodied carbon as it also furthers efforts to decarbonise all contributing parts of the new construction. For instance, gas heating will be made infeasible as the only source of energy in new builds under RE2020. But the overarching strategy is to strengthen the reliance on frugality and best design practice through the reduction of the 'Bbio' factor reflecting the bioclimatic efficiency [fabric efficiency] of the building. This factor is calculated considering :
The building envelope thermal performance based on its thermal conductivity along with thermal bridging evaluation.
The building envelope air tightness given the ventilation system and air leakage which should then be verified.
The requirement for heating or cooling as estimated based on solar energy intake. This relies on orientation, the rate of opaque to clear surfaces, nearby solar masking and building usage.
Aside from carbon counting and bioclimatic design, RE2020 adds a requirement on maximum cumulative time of summer discomfort and continues setting thresholds on primary energy use, introducing one specifically on non-renewable sources. The state of discomfort is reached when the temperature rises above 26°C to 28°C during the day and does not decline below 26°C at night.
All is good and well, but how groundbreaking is it?
A few elements of the regulation have been announced, causing both expectations and outcry, pressure and interests are being exposed and applied to law-makers but how exactly is the RE2020 an improvement towards the general objectives that are to be met?
The French Institute for Building Performance (IFPEB), along with energy-experts Pouget Consultants, put a selection of real, existing buildings to the test of the provisional RE2020 and its calculation method. The results, although partial, shed some light onto the debate and further challenges.
Among the three case study projects, two are built out of reinforced concrete (projects 1 & 2) while the third is built using CLT (project 3). Their energy sources are quite different too, ranging from collective gas boiler (project x) to district heating with about half sourced from renewables (project x). Here’s the rundown of how the three buildings fare against the expected values for 2022 and 2025:
So in 2022, most of the buildings would pass the regulation on most criteria. A review of the projects identifies simple paths of improvement to bring back all projects within the 2022 criteria.
But the case studies paint a different picture for 2025 where the requirements increase. Operational carbon of the project 1 would be about twice the 2025 requirement while project 3, although built using carbon-storing timber, would meet the 2025 embodied carbon requirement with only 3% of margin.
Looking at 2028 and 2031 objectives, all three projects would be even further from passing but the government plans on global decrease of carbon emissions and energy grid improvements to ensure the aim can be met for this period. The latter improvements are partially reflected in the conversion factor for electricity from final to primary energy which is a topic that caused much debate between the government and energy professionals.
Judging on those few cases, RE2020 sure is challenging but it won’t be world-breaking until 2025. The regulation is designed with progressivity in mind and it shows. Ensuring both a prompt reaction to the challenges faced by our society and a progressive skilling of the industry is a complicated balance to find. France is willing to take measures and apply RE2020 to lower the impact of the construction sector, which to this day represent about 29% of the national carbon footprint.
Joe Giddings concludes, the example being set by France is highly applicable to the UK, showing the level of ambition that is required of a country with an economy as large as the UKs. We wanted to illustrate this with a building that meets at least some of the new criteria being set in France, to demonstrate that good-for-the-climate can be good for your eyes too. The project pictured, by MARS Architectes, whilst not measured against the E+C- test, meets a number of French environmental criteria; 'Effinergie', Biosource niveau 3 (highest level of bio-based certification) & Biodiver-city (biodiversity label), and is an urban densification scheme, increasing inhabitation within an already dense urban centre. For more on the project, see here.
Frédéric Bourgeon, ACAN Embodied Carbon group member
Frédéric is a structural engineer with experience ranging from major bridges to buildings both new and renovated. He currently develops an engineering consultancy dedicated to natural materials.
Joe Giddings, ACAN Campaigns Coordinator
Joe is a London based architect and designer who studied at the Royal Danish Academy (KADK) and Oxford Brookes University. He is Projects & Campaigns Director, Timber Accelerator Hub at Alliance for Sustainable Building Products, and Campaigns Coordinator at ACAN.
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