Obligation to insulate buildings during roof renovations or repairs

Verified 29 July 2025 - Directorate of Legal and Administrative Information (Prime Minister)

During important work of overhaul or refaction roofing of existing buildings, thermal insulation work must be carried out. There are some exceptions. We explain the regulations.

Buildings concerned

Works ofthermal insulation must be carried out during major roofing or renovation work on existing buildings. That applies to buildings for use:

  • Housing
  • Desktop
  • Of commerce
  • Teaching.

This also applies to hotels.

Buildings excluded

That obligation does not apply the following categories of buildings:

  • Buildings and parts of buildings in which no energy is used to regulate indoor temperature
  • Temporary constructions intended for a period of use equal to or less than 2 years
  • Independent buildings with a floor area of less than 50 m²
  • Buildings for agricultural, craft or industrial use, other than residential premises, which require only a small amount of energy for heating, domestic hot water production or cooling
  • Buildings serving as places of worship
  • Buildings that received the label “Remarkable contemporary architecture”
  • Historic monuments classified or inscribed to the inventory, where this would have the effect of altering their character or appearance in an unacceptable manner.

The regulations depend on the type of work to which the building is subjected:

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Renovation of facade

General case

The developer must carry out thermal insulation work on the walls concerned by renovation work. This applies when all of the following conditions are met:

  • The walls that are the subject of renovation work:
    • Are walls of heated premises overlooking the outside.
    • Are constituted on the surface at more than 50%, excluding openings, of terracotta, concrete, cement or metal.
  • The renovation work concerns, on at least 50% of a wall of a building, excluding openings:
    • Either the refurbishment of the existing plaster
    • Either the replacement of an existing facing
    • Either the installation of a new facing.
Exceptions

There may be exceptions to that obligation, in the following cases:

  • If there is a risk pathology of the frame related to any type of insulation. The developer must then justify the technical risk incurred by producing a reasoned note written by a person skilled in the art under his responsibility.
  • If the insulation work does not comply with easements or may not comply with the rules relating to the right to land, the right to property or the appearance of facades and their location. For example, if the insulation work did not comply with obligations concerning citizenship or rights-of-way.
  • If the insulation work leads to changes in the condition of the exterior parts or architectural and decorative elements of the construction in contradiction with the requirements laid down for the remarkable heritage sites, the surroundings of historical monuments, the registered and classified sites, or with the rules and requirements set out in the Local Urban Plan (PLU).
  • If there is a clear disproportion between the advantages of insulation and its disadvantages of a technical, economic or architectural nature. This applies in particular if the improvements brought about by this insulation have too great a negative impact in terms of the quality of the use and operation of the building, of the modification of the external appearance of the building with regard to its architectural quality, or of additional cost.

One manifest disproportion return on investment time is systematically established, in the case of a facade renovation, in the following cases:

  • Building built after 2001
  • Isolated façade after 2008
  • Facade already insulated so as to obtain a thermal resistance greater than or equal to 2.3 m².K/W (for example with 8 cm of mineral wool, 9 cm of polystyrene, 10 cm of wood fiber insulation or 10 cm of hemp wool)
  • Building that has already been subject to an energy audit (less than 10 years old) that has demonstrated that insulation is not appropriate (technical, legal, architectural or economic constraints described above)
  • Presence of balconies with a depth of less than 1 m
  • Insulation work requiring the identical reconstitution of existing models
  • Insulation work requiring asbestos removal work.

Otherwise, the obvious disproportion is established in the following situations:

  • Either if insulation from the outside would significantly degrade the architectural quality. The developer shall justify the heritage or architectural value of the façade and the damage incurred, by producing a reasoned note written by an architect or by a person approved in architecture or holding a receipt and entered in a regional architects' register or its annex.
Who shall I contact
  • Either if the return on investment of the additional cost induced by the addition of insulation, net of public financial aid, is more than 10 years. The plate taken into account to calculate this additional cost includes the cost of insulation work and all other costs related to the addition of insulation. The client justifies the time of return on investment either by producing a note produced by a person skilled in the art under his responsibility (experienced specialized personnel), or by establishing that its duration is greater than 10 years by comparison of the building to the referenced standard cases.

The method of calculating the time of return on investment is available on pages 8 to 10 of a dedicated guide published by the Ministry of Construction and the Agency for Ecological Transition (ADEME).

Roof Rehabilitation

General case

The developer perform thermal insulation work on the roof or the top floor of the last occupied or heated level when a building is undergoing roof repair work, if the work involves replacing or covering at least 50% of the entire cover, excluding openings.

Exceptions

There may be exceptions to that obligation, in the following cases:

  • If there is a risk pathology of the frame related to any type of insulation. The developer must then justify the technical risk incurred by producing a reasoned note written by a person skilled in the art under his responsibility (competent specialized personnel).
  • If the insulation work does not comply with easements or may not comply with legislation or regulations relating to soil law, property rights or the appearance of facades and their location. For example, if the insulation work did not comply with obligations concerning water flow or sunshine.
  • If the insulation work leads to changes in the condition of the exterior parts or architectural and decorative elements of the construction in contradiction with the requirements laid down for the remarkable heritage sites, the surroundings of historical monuments, the registered and classified sites, or with the rules and requirements set out in the local urban plan (PLU)
  • If there is a clear disproportion between the advantages of insulation and its disadvantages of a technical, economic or architectural nature. This applies in particular if the improvements brought about by this insulation have too great a negative impact in terms of the quality of the use and operation of the building, of the modification of the external appearance of the building with regard to its architectural quality, or of additional cost.

One manifest disproportion return on investment time is systematically established, in the case of roof repairs, in the following cases:

  • Building built after 2001
  • Roof or high floor of the last inhabited level insulated after 2008
  • Roof or high floor of the last inhabited level already insulated so as to obtain a thermal resistance greater than or equal to 2.5 m².K/W (for example with 10 cm of mineral wool or polystyrene, 12 cm of wood fiber insulation or 12 cm of bulk cellulose wadding).
  • Building that has already been subject to an energy audit (less than 10 years old) that has demonstrated that insulation is not appropriate (technical, legal, architectural or economic constraints described above)
  • Insulation work requiring asbestos removal work.

Otherwise, the obvious disproportion is established in the following situations:

  • Either if insulation from the outside would significantly degrade the architectural quality. The developer shall justify the heritage or architectural value of the façade and the damage incurred, by producing a reasoned note written by an architect, a business of architects or by a person approved in architecture or holding a receipt and entered in a regional architects' register or its annex.
Who shall I contact
  • Either if the return on investment of the additional cost induced by the addition of insulation, net of public financial aid, is more than 10 years. The basis of assessment used to calculate this additional cost includes the cost of insulation work and all other costs associated with the addition of insulation. The contracting authority justifies the return on investment time either by producing a note produced by a person skilled in the art under his responsibility, or by establishing that its duration is greater than 10 years by comparison of the building with the reference standard cases.

The method of calculating the time of return on investment is available on pages 8 to 10 of a dedicated guide published by the Ministry of Construction and the Agency for Ecological Transition (ADEME).

FYI  

The thermal insulation work of walls, floors and roofs must be carried out in accordance with the requirements indicated in an order available on Légifrance:

Requirements related to building insulation work

Legifrance

Pour en savoir plus

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