The carbon neutrality objective in construction: from theory to reality

In 2015, the Paris Agreement set its signatory parties the target of limiting the rise of global temperatures to 1.5 degrees maximum by 2030. The latest IPCC report, presented in October, makes it clear that this target will not be met if action is not taken quickly to limit the carbon footprint created by human activities and that the consequences for the environment will be devastating.

Conférence Zéro Carbone

The group of experts called for action to reduce greenhouse gas emissions, starting with the sectors that produce the most such as residential and non‑residential construction, which produces 20% of emissions in France. Although it is not the sector with the highest emissions — a title belonging to the transport sector, which produces 28% of emissions — it remains one of the main areas for action in the energy transition. In order to achieve the objectives of its international agreements, the French government has published an ambitious Climate Plan that aims to reduce the country’s greenhouse gas emissions by 75% by 2050, compared to those of 1990.

How can this National Low‑Carbon Strategy be applied in the construction sector?  Which means and tools can be used to carry out this transformation?

Leonard organized an initial overview of the topic with four industry experts on December 4 to better understand the challenges of carbon neutrality and the methods being used to achieve it.


Getting to the heart of carbon neutrality

In order to understand the objectives for construction, we first need to look at the definition of the concept itself. What do we mean when we talk about “carbon neutrality”? Which indicators to we use for calculation, and how do we determine which are the most important? And which stage in a building’s life cycle has the most impact on the final diagnosis?

For Mathieu Tamaillon, managing director of Sinteo, calculating a building’s carbon footprint involves three categories of emissions:

  • Direct on‑site carbon emissions, produced by the energy consumed by the building (e.g. from boilers, etc.)
  • Off‑site carbon emissions, particular those of power plants supplying the building with electricity
  • Carbon emissions linked to making the materials needed for the building’s construction

Carbon emissions are calculated in square meters; an office building built in the 1960s emits 3 metric tons of carbon per square meter per year, just through energy usage. New structures that are built according to the French 2012 Thermal Regulation standard (RT 2012) emit no more than 1.5 metric tons of carbon per square meter, halving emissions. A promising start, but not enough given the new targets of the future 2020 Environmental Regulations (RE 2020) — less than one metric ton of CO2 per square meter.

There are many ways of meeting this target, whether it’s through the materials chosen, how we deal with peak electricity usage or by way of the circular economy. “Most people don’t understand that the era of abundance is over and that we are now going to have to see waste as something that must be completely recycled. It is a lifeline for reducing our impact on the environment.” The potential is considerable — the construction sector produces 40 million metric tons of waste in France every year, a majority of which is produced by structural works and can be transformed and reinvested in other projects. “It’s all the small wins that add up to make a good footprint.”

Conf Zéro carbone Bruno Peuportier

Bruno Peuportier, head of research at the Mines ParisTech Graduate School and member of the VINCI‑Paris‑Tech Eco‑design Chair, specifies the role of materials in a building’s carbon footprint, taking into account its entire life cycle. He also underlined the importance of paying attention to the potential impact of concrete substitute materials — not simply replacing one form of pollution with another.


Shaping a low‑carbon future, from methods to projects

Given this definition, how can we actually measure a building’s energy performance and carbon footprint?

The calculation tools are essential for measuring the efforts needed to meet the new regulatory requirements. Created in 2017, the French E+C– (carbon‑energy) label, which prefigures the future environmental regulations for new buildings (RE 2020), aims to promote the construction of energy‑positive buildings by requiring a carbon‑footprint assessment of all new builds. Taking carbon into account is not the only new requirement being brought about by the label, however. Lucie Rémir, a sustainable performance engineer at VINCI Construction France, also reminded us that the label will take all of a building’s uses into account for the first time, including extraneous ones (elevators, lighting, parking etc.). The other big change lies in the calculation of buildings’ greenhouse gas emissions by analyzing their life cycles and thus taking all their emissions into account, from design to operation to decommissioning.

Conférence Zéro Carbone Lucie Rémir

A variety of tools and databases combine, making it possible to assess the performances of buildings in terms of energy and the environment. If data for choosing which energy carrier to use is not available in advance, the Vizcab tool can be used to capture a building’s volumetric measurement in order to experiment with different settings and obtain estimates of CO2 emissions. To complete the range of tools available, VINCI Construction France has also developed an internal tool to facilitate the integration of data from multiple databases for an estimation of a building’s emissions. During the tendering phase, builders can use these results to refine their propositions in order to meet the required carbon performance levels.

Once the objectives have been met in the calculations, how can we make low‑carbon ambitions a reality in the field? There are still very few buildings that can claim the E+C– label, but some projects are consistent with this aim of reducing their carbon footprint. This is the case for Rêve de Scènes Urbaines (a dream of urban scenes), an industrial demonstrator for sustainable cities that has been set up in the Parisian suburb of Plaine Commune, presented by Raphaëlle Vert. Restraint is the word at the site in Plaine Commune when it comes to costs, energy, carbon and materials. These characteristics are used to determine the nature of the projects chosen from the proposals of the collective of 70 business that have partnered up with the demonstrator, which is led by VINCI, Veolia and Artelia. Cycle Up is one of them. Supported by the Caisse des Dépôts, this digital contact platform that aims to encourage the reuse of materials will have a physical presence there. Cycle Up will regroup waste collection, sorting and recycling streams so that new outlets can be found for new materials, all while pooling the initial investment.

Conférence Zéro Carbone Raphaelle Vert

This event was the first of a series of three meetings dedicated to the challenges of the carbon neutrality objective in construction. The next round table, which will take place January 16 at Leonard:Paris, will focus on the role of construction materials in buildings’ carbon footprints. Are conventional materials compatible with the new requirements? What alternatives are coming into play? Find out January 16 at 7pm!

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