How does RE2020 measure the environmental impact of new buildings?

The building sector is responsible for 25% of greenhouse gas emissions in France. In this context, RE2020 is strengthening its requirements around three major objectives: ensuring summer comfort, optimizing the energy performance of new buildings, and reducing their carbon impact throughout their lifetime (50 years). So how does RE2020 measure the environmental impact of buildings?

Background and challenges

RE2020 aims to reduce the impact of new buildings on climate change by taking into account their entire life cycle. Thus, all of the impacts on climate change associated with the building are taken into account and assessed in RE2020, from the construction phase to the end of the building's life, including the operational phase.

On the one hand, this encourages construction methods that emit few greenhouse gases or enable their storage, such as the use of bio-based materials. On the other hand, it encourages the consumption of carbon-free energy sources. For the first time, the regulations set a maximum threshold for the impact on climate change for energy consumption and construction (building components and construction sites).

How is environmental impact taken into account?

Environmental performance introduces the calculation of a building's environmental impact throughout its entire life cycle. This assessment is based on the principle of life cycle assessment (LCA). LCA makes it possible to objectively measure a building's impact through a series of environmental indicators calculated at every stage of its life cycle.

The 5 stages of a building's life cycle

RE2020 distinguishes between five stages:

Step 1 – Production phase: acquisition of raw materials and transformation into manufactured products (+transport).
Step 2 – Construction phase: process of construction and installation of materials and finished products, construction site (+transport).
Step 3 – Operational phase: use, maintenance, repair, replacement of materials and finished products, energy and water consumption during building use.
Step 4 – End of life: treatment and disposal of materials and finished products (+transport).
Step 5 – Benefits and costs beyond the life cycle: potential for reuse, recovery, and recycling.

The 5 categories of contribution to environmental impacts

For each phase of the life cycle, the method takes into account the contribution to environmental impacts of the five categories that make up the building:

1. Contribution relating to "components": environmental impact of producing, transporting, installing, using, and demolishing building construction products and equipment (heating, air conditioning, ventilation, etc.). This contributor covers stages 1 to 5 of the building's life cycle.
   
2. Contribution related to "energy": environmental impact of energy imported and consumed by the building during its operation. This contributor corresponds to the energy consumed during stage 3 of the building's life cycle.
   
3. Contribution relating to "water": covers all water uses at the building level and the management of rainwater collected by the building, as well as its treatment. This contributor is involved in the operational phase (stage 3 of the life cycle). This data must be provided, even though it has no impact on regulatory indicators.
   
4. Contribution relating to the "construction site": environmental impact of energy consumption at the construction site (stage 2 of the life cycle), water consumption and discharge at the construction site, disposal and treatment of earthworks waste, and components used to build temporary structures necessary for the construction site.
   
5. Contribution relating to the "plot": covers all components necessary for structures on the plot, excluding buildings, networks, energy production systems, and parking lots. These elements must be reported, but do not affect regulatory indicators. As with the contribution relating to components, stages 1 to 5 of the building's life cycle are covered.

Calculation of contributions

All contributions to environmental impacts are calculated for each phase of the life cycle and follow the same principle: linking project data (product quantity, energy quantity from the energy calculation, construction site data, etc.) to relevant environmental data that provides the unit impacts associated with this project data. This is referred to as a functional unit.

Depending on the calculated contribution, the quantity may correspond, for example, to quantities of components (units,^m², ml, etc.), energy (kWh of energy consumed), or water (^m³).
The environmental data required for environmental assessment under RE2020 is collected in the INIES database (http://www.inies.fr) and can be consulted free of charge.
The adjustment factor may consist, for example, of a renewal factor linked to the lifespan, dynamic weighting, or adjustment of the quantity to the functional unit used in the unit environmental data.

Climate change impact assessment subject to regulatory requirements

The assessment of environmental performance is broad, and the impact of each contribution must be calculated. However, not all of them have an impact on regulatory indicators. In fact, only contributions relating to "components," "construction," and "energy" are targeted by regulatory indicators.

Each construction product, piece of equipment, and service is characterized by its environmental data (comprising 27 environmental criteria). RE2020 regulates only one of the environmental impacts assessed by the LCA: the impact on climate change. In order to be consistent with energy performance indicators, this is reduced to the regulatory surface area and is called_ICbâtiment to represent all the impacts of the operation on climate change.

The_ICbâtiment index

The "components" and "energy" contributors have the greatest impact and often account for around 90% of the total impact of an operation. In order to activate levers for action and work simultaneously on these contributions, RE2020 specifically regulates the_ICenergy index and the_{ICconstruction} indicator, which corresponds to the sum of the "components" and "construction site" contributions.

These two indicators can be used to represent the impact of a new building on climate change.

Its unit is kg_CO2 eq/^m2.

The_{ICconstruction} index

The_{ICconstruction} index represents the impact of "components" and "construction site" contributions: it is therefore the impact on climate change of construction products and equipment and their implementation.

Its unit is kg_CO2 eq^/m2 of SHAB or SU.

The IC index_energy

The_ICénergie index represents the impact of the "energy" contributor: it is therefore the impact on climate change of energy consumption during the life of the building. This indicator has two objectives: to reduce the building's energy consumption and to decarbonize it as much as possible. It is also taken into account in measuring the energy performance of a new building in RE2020.

Its unit is kg_CO2 eq^/m2 of SHAB or SU.

Find out everything you need to know about the RE2020_ICénergie index >

Two possible calculation approaches

The environmental impact of each contributor can be calculated using either a detailed or simplified calculation: 

Simplified approach: to facilitate the assessment of the building's environmental impacts

– In order to compensate for the lack of data, certain lots or sub-lots of the contribution relating to "Components" may be supplemented by flat-rate values provided by the Ministry responsible for construction; – The same applies to lot 0 of the contribution relating to the "Plot";  – Simplified calculation formulas are proposed for calculating the impacts of contributions relating to "Construction Site" and "Water."

Detailed approach: to enable exemplary project owners to showcase their efforts

Detailed calculation of all lots and use of actual project data.

Example of a fictitious environmental impact calculation for a wooden beam:

This example illustrates the impact of weighting on end-of-life considerations. One of the characteristics of wood, or bio-based materials, is that they capture_CO2 during their growth.
The carbon footprint at the beginning of the life cycle is therefore very favorable (negative emissions in the example).
This captured_CO2 is stored in the building during its lifetime and then released back into the environment at the end of the product's life, according to environmental data assumptions.
Overall, the impact of wooden beams on climate change appears to be beneficial after taking into account the timing of emissions.
Thus, for components whose main emissions occur at the beginning of their life cycle, the dynamic approach gives a result very close to that of the static approach.

Environmental performance is the major regulatory change introduced by RE2020, which requires the calculation of a building's environmental impact throughout its entire life cycle. This assessment is based on life cycle assessment (LCA), which objectively measures a building's impact using a series of environmental indicators. LCA incorporates all stages from the extraction of materials needed to produce construction products and equipment, to the demolition of the building at the end of its life and the resulting waste treatment.

Source: RE2020 Guide published by CEREMA and the Ministry for Ecological Transition (March 2022 version)