Renovation: in which cases should thermal insulation work be undertaken?

Verified 27 July 2022 - Directorate for Legal and Administrative Information (Prime Minister)

You have an obligation to do thermal insulation work when you undertake major renovations. These can include the renovation of the walls of heated spaces overlooking the outside, the conversion of a garage into a living room, or heavy roof repairs. There are, however, cases of exemption.

Thermal insulation applies to the following buildings or parts of buildings:

  • Individual dwelling
  • Collective dwelling building
  • Offices
  • Shops
  • Educational building
  • Hotels

This obligation does not apply the following buildings or parts of existing buildings:

  • Buildings and parts of buildings where no energy is used to regulate indoor temperature
  • Provisional construction planned for a period of use of 2 years or less
  • Independent buildings including the floor area is 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
  • Places of worship
  • Historical monuments classified or listed in the inventory

Please note

The obligation to isolate a building undergoing renovation does not apply to Guadeloupe, Guyana, Martinique, Reunion and Mayotte.

Facade renovation

The major overhaul of a building includes the rebuilding of the existing plaster or the addition or replacement of a facing. When it concerns at least 50% of the facade without opening of a heated building, you need to achieve thermal insulation of the burned walls.

This obligation applies to facades consisting of walls composed of terracotta, industrial bricks, industrial or similar concrete blocks, banched concrete or metal cladding.

The obligation shall not apply to facades consisting of moisture-sensitive materials. These include, for example, façades made of stone, raw earth, cob, wood, and handmade materials such as traditional lime plaster.

In order to facilitate the work of thermal insulation from the outside, the competent authority issuing thecity planning authorization necessary may exclude certain rules from the MORE: titleContent on the following points:

  • Distances of the buildings by allowing protruding insulation within 30 cm
  • Ground right of way after work exceeds authorized right of way

You must obtain from the competent community a authorization to occupy public domain to ensure that the insulation project does not compromise the safety and circulation of the street or public space concerned.


The owner of an existing building who insulates his building from the outside shall have a right of overhang of the neighboring building's land of not more than 35 cm.

Fitting-out works to make premises habitable

The thermal insulation of a residential building must be carried out as soon as you install a room of more than 5 m² of floor area to make it habitable.

This concerns the fitting-out of attics, the transformation of a garage or any other non-habitable, non-buried or semi-buried room.

You must isolate opaque walls of the space created. These are: low floors that overlook the outside or an unheated room, roofs (sloping or terraced roofs) and walls that overlook the outside.

Roofing work

You perform rehabilitation work roofing on at least 50% of its surface or you settle a roof. You must insulate your roof or the high floor from the top floor occupied and heated.

Please note

this obligation does not apply to cleaning, defoaming and waterproofing which are not considered to be roof repairs.

The roof may be insulated by raising it up to a maximum of 30 cm above the maximum height laid down in the MORE: titleContent.

The extra thickness or the raised area must be adapted to the technical and architectural characteristics of the facade or roof.

You may not need to perform thermal insulation work because oftechnical or legal impossibility in the following cases:

  • Risk of damage to the frame related to the insulation certified by a professional of the building.
  • Risk of non-compliance of work with easements or rules relating to the law of the ground (height or right of way for example) or to the appearance of facades or to their layout
  • Modification of the condition of the external parts or of the architectural and decorative elements in contradiction with the rules laid down in the remarkable heritage sites categorized
  • Vessel having been awarded the label Remarkable contemporary architecture

You can also be exempted from this insulation work if there is a disproportion between the advantages of insulation and its disadvantages of a technical, economic or architectural nature.

The disadvantages of economic must be substantiated by a score drawn up by a construction professional. They may also be justified by a document produced by the developer establishing that the time to return on investment is more than 10 years.

The disadvantages of architectural must be confirmed by a reasoned note from an architect.