Thin insulation and RE 2020 in France: no minimum R per wall

Which buildings does the RE 2020 apply to?

The 2020 environmental regulation (RE 2020) was created by Decree No. 2021-1004 of 29 July 2021 and the order of 4 August 2021. It appears in Articles R. 172-1 et seq. of the French Construction and Housing Code, and applies to building permits and prior declarations filed:

• since 1 January 2022 for detached or semi-detached houses and apartment buildings;
• since 1 July 2022 for offices and primary and secondary school buildings;
• since 1 July 2023 for temporary buildings;
• since 1 May 2026 for thirteen new categories, including hotels, shops, restaurants, healthcare facilities, sports facilities and industrial and craft buildings.

It also applies to extensions of existing buildings, with requirements adapted to their use and floor area. Other renovation work falls under other rules. It does not apply in Guadeloupe, French Guiana, Martinique, La Réunion and Mayotte, which have their own regulations.

Requirements for the building, not for each wall

Article R. 172-4 sets five performance requirements, calculated for the whole building:

• Bbio, the bioclimatic need, which reflects the quality of the design and of the envelope (insulation, orientation, glazing);
• Cep and Cep,nr, total and non-renewable primary energy consumption;
• Ic énergie, the carbon impact of energy consumption;
• Ic construction, the carbon impact of products and equipment over their life cycle;
• DH, degree-hours of summer discomfort.

The limits are adjusted according to climate, altitude, floor area and building category, among other factors. The average reference value of the Bbio (Bbio_maxmoyen) is 63 points for a detached or semi-detached house and 65 points for an apartment building, before the adjustment coefficients are applied.

Means requirements, set by the order of 4 August 2021, come on top. Air permeability Q4Pa-surf is limited to 0.60 m³/(h.m²) in detached or semi-detached houses and 1.00 m³/(h.m²) in apartment buildings; in housing, it is demonstrated by a measurement or by a quality approach (Article 17). Other requirements concern thermal bridges and natural light: for the latter, Article 23 offers a choice between illuminance and view criteria, and a glazed area of at least one sixth of the reference floor area.

How the calculation counts reflective insulation

Product characteristics are set by the Th-Bat 2020 rules, annexed to the order (consolidated version of 29 April 2026). Their “Opaque walls” volume has a section on reflective products. Unless values are given in an Avis Technique, the wall coefficient is calculated as follows: Up = Uc + ΔU, with Uc = 1 / (Rr + RL + Rp).

• Rr, the product's own resistance: determined according to standard EN 16012, or given by a European Technical Assessment or an Avis Technique; failing that, a default value (0.20 m²K/W for a 10 mm multilayer product, 0.40 for 20 mm).
• RL, the resistance of each air gap, read from a table according to its thickness, its ventilation, the direction of heat flow and the emissivity of the reflective face.
• Rp, the linings, the other insulation materials and the surface resistances.
• ΔU, the thermal bridges of the fixings: 0.08 W/(m².K) by default on timber frames.

Emissivity is the decisive point. The rules are explicit: if the emissivity is not given in an Avis Technique, the calculation uses 0.5 for an unventilated air gap. Yet it is the low emissivity of the aluminium, 0.053 as measured by the LNE on the R'BULL Pro 13, that makes the air gaps perform.

The two “Th-Bat 2020 calculation” rows are indicative calculations by Ceilingo, using the values in Table 76 of the rules (air gaps of at least 2 cm, horizontal heat flow), excluding thermal bridges: the thermal engineer must confirm them for each wall.

In the KTU report, the product's own resistance, 0.29 m²K/W, is determined by testing according to EN ISO 22097:2023 (the Th-Bat rules still cite EN 16012, which this standard replaced in 2023). The resistance of the two air gaps, and therefore that of the whole assembly, is calculated according to EN 16863 Annex D and EN ISO 6946, with a declared emissivity of 0.05. The emissivity of 0.053 was measured separately by the LNE. The gap between 1.35 and 1.60 m²K/W comes from the calculation conditions: the Th-Bat table assumes 0 °C outside and 20 °C inside, the KTU calculation a difference of 5 K per air gap around 10 °C.

How to have the low emissivity taken into account

The Th-Bat rules cite only one document for the emissivity of air gaps: the Avis Technique (or Document Technique d'Application), issued by the CCFAT, the French committee responsible for Avis Techniques, and processed by the CSTB. It can also directly provide values applicable to the wall.

Failing that, the calculation with an emissivity of 0.5 gives a cautious value: that is the one to use when sizing the main insulation.

What about the carbon assessment?

The Ic construction indicator adds up the impact of all products over their life cycle. Each product enters it through its environmental and health declaration (FDES) published in the INIES database or, failing that, through a default environmental value provided by the ministry (Article 16 of the order).

These default values are deliberately penalising: the ministry's procedure applies a safety coefficient of 30 % when it draws on several equivalent sheets or on generic data, and of 100 % when a single sheet serves as the basis, on top of an already cautious calculation. Such values exist for insulation based on reflective films. At the date this page was updated, Ceilingo had not identified any R'BULL environmental declaration published in the INIES database: a default value therefore applies.

From 2028, heavy use of default values also lowers the project's permitted limit.

In renovation, other rules apply

The RE 2020 does not apply to work on an existing building. In renovation in France, minimum thermal resistances, wall by wall, are set by the “element by element” thermal regulation and by the conditions of the grants.

For energy savings certificates (CEE) in France, the sheets in force require a resistance of at least 7 m²K/W in unconverted lofts and 6 in sloping roofs (BAR-EN-101), 3.7 for walls (BAR-EN-102) and 3 for ground floors (BAR-EN-103). Existing insulation is not counted, and the resistance of reflective insulation is assessed under standard NF EN ISO 22097. These sheets expressly provide for several insulants installed one over the other: the declaration then states the brand and reference of each one and the overall thermal resistance. R'BULL Pro 13 is therefore combined with a traditional insulant to reach the required threshold.

In France, since 1 September 2026, MaPrimeRénov' no longer funds insulation as a single measure (Decree No. 2026-822 of 25 August 2026). Insulation is still funded within a major renovation: the order of 17 November 2020 accepts one or more insulating materials whose total thermal resistance reaches the threshold of the part treated, and standard NF EN ISO 22097 is expressly recognised there for reflective insulation. CEE grants, for their part, continue to fund insulation measure by measure.

What to remember for a new-build project

1. Design the thin insulation as a complement. It improves the wall, but without an Avis Technique the calculation counts it as slightly under 1 m²K/W with two 20 mm air gaps.
2. Take care of the air gaps. Their resistance depends on their thickness, their ventilation, the direction of heat flow and the emissivity of the faces. At equal emissivity, a slightly ventilated air gap loses about half its value, and a well-ventilated one no longer counts: the configuration must match the conditions of the Th-Bat rules.
3. Send the supporting documents to the thermal engineer. Declaration of performance, thermal resistance, emissivity and reaction-to-fire reports: everything is published on our Test reports page.
4. Check the rest of the wall. The product is highly vapour-tight: its position must rule out any risk of condensation. The reaction to fire required depends on the type of building.