Why RE2020 changed practice

RE2020 replaced RT2012 for new buildings in France, beginning with housing in 2022, and it extends to offices and primary/secondary schools as well. Its purpose is threefold: reduce energy demand, cut lifecycle carbon emissions, and improve comfort during heatwaves. For architects, this means the building envelope, massing, orientation, material palette, and technical systems now have to be aligned much earlier than before.

The five indicators

RE2020 is often explained through five main indicators: Bbio, Cep, Cep,nr, DH, and Ic. Bbio measures bioclimatic needs, Cep measures total primary energy use, Cep,nr measures non-renewable primary energy, DH measures summer discomfort, and Ic measures lifecycle carbon impacts. In practice, these indicators are not separate silos; a choice that helps one can hurt another, so the design strategy has to be integrated from day one.

Bbio: design the envelope first

Bbio reflects the building’s need for heating, cooling, and lighting, independent of the systems chosen. It is driven by the quality of the envelope, compactness, orientation, glazing balance, solar gains, daylight access, insulation, airtightness, and thermal inertia. For architects, this means you should optimize the plan and section before you discuss mechanical systems, because a strong envelope gives you more room to satisfy the rest of RE2020.

Cep and Cep,nr: choose systems wisely

Cep covers total conventional primary energy for heating, cooling, domestic hot water, lighting, ventilation, and auxiliaries, plus some additional uses in collective buildings. Cep,nr focuses only on the non-renewable share, so it rewards lower-carbon energy vectors and penalizes dependence on fossil or electricity-heavy solutions when they are not well designed. The practical lesson is simple: a building that is efficient on paper but relies on a poor energy mix can still struggle, so system choice matters as much as geometry.

DH: summer comfort is now structural

DH, or degree-hours of discomfort, measures how long and how intensely indoor temperatures exceed comfort thresholds during hot periods. RE2020 uses DH because previous indicators were not closely enough linked to actual discomfort, especially under future climate conditions. Architects can improve DH performance with passive strategies such as cross-ventilation, solar protection, night cooling potential, thermal mass, and limiting excessive east-west glazing.

Ic: carbon is part of design

Ic includes the climate impact of construction products and equipment over the building life cycle, and RE2020 also distinguishes the carbon linked to energy use during operation. This is a major shift because the carbon cost of materials like concrete, steel, and technical equipment is now part of regulatory design thinking. In response, architects should compare structural systems, reduce unnecessary material quantities, and consider lower-carbon or biobased alternatives when they fit the project.

How to design for RE2020

The best RE2020 projects start with a bioclimatic concept, not a technical patch at the end. First, shape the building to reduce demand; second, improve comfort passively; third, select low-carbon systems and materials; and fourth, verify the indicators as the design evolves. A useful rule of thumb is to treat energy, comfort, and carbon as one conversation rather than three separate reports.

Practical checklist

• Orient and compact the building to support Bbio.
• Balance glazing for daylight, solar gains, and summer control.
• Specify airtightness and thermal-bridge treatment early.
• Test passive cooling strategies before adding mechanical cooling.
• Compare heat pump, gas, district heating, and renewable options against Cep and Cep,nr.
• Reduce embodied carbon by cutting material quantities and choosing lower-carbon assemblies.
• Run iterative simulations instead of waiting for the final compliance study.

What architects should remember

RE2020 rewards integrated design, not late-stage optimization. The architect’s role is central because most of the performance is locked in by the first spatial and material decisions. If you treat Bbio, Cep, Cep,nr, DH, and Ic as design drivers rather than regulatory hurdles, the project is much more likely to be compliant, comfortable, and carbon-aware.