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When should thermal insulation work be undertaken?

Verified 04 May 2020 - Directorate for Legal and Administrative Information (Prime Minister)

Thermal insulation of an existing building is mandatory if you are undertaking major renovation work. This may include the remodeling of the walls of heated rooms facing the outside, the transformation of a garage into a living room, or heavy work on roof repairs. There are, however, cases of exemption.

The obligation of thermal insulation concerns buildings or parts of buildings located in metropolitan areas.

It is essential for buildingsindividual and collective housing, offices, shops, education and hotels..

This obligation shall not apply to the following existing buildings or parts thereof:

  • Buildings and parts of buildings in which energy is not used to regulate internal temperature
  • Interim construction for a duration of use equal to or less than 2 years
  • Independent buildings including floor surface is less than 50 m2
  • Buildings agricultural, artisanal or industrial use, other than residential premises, which require only a small amount of energy for heating, hot water or cooling
  • Buildings used as places of worship
  • Historical monuments classified or listed in the inventory

When you start a major ravaging from the facade of a heated building, you must carry out thermal insulation work.

A refit is important when it involves either the refurbishment of the existing coating or the addition or replacement of a siding. In this case, thermal insulation is mandatory if the facade is at least 50% refurbished without opening.

Insulation works apply to facades made up of walls composed of industrial bricks, industrial or similar concrete blocks, white concrete or metal cladding.

The thermal insulation requirement does not apply to façades with materials sensitive to humidity (stone, raw earth, cob, wood, handmade materials such as traditional lime coating, for example).

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

This concerns, for example, the fitting out of attic space, the transformation of an annex garage, or any other uninhabitable room not buried or semi-buried. You must then isolate the opaque walls. These are the low floors that overlook the outside or an unheated room, the roofs (sloping or roof terraces) and the walls that overlook the outside.

Please note

you are exempted from performing thermal insulation work if it creates a risk of building degradation. This risk must be certified by a building professional.

You must insulate your roof if you are making repair work on at least 50% of its surface or when you install an overroof.

Please note

this obligation does not apply to cleaning, frothing and waterproofing which are not considered as roof repair work.

Derogations from the thermal insulation requirement apply only to work on the repair and repair of roofs.

You may be exempted from performing thermal insulation work for technical or legal impossibilities in the following cases:

  • Risk of structural degradation due to insulation
  • Risk of non-compliance with easements or rules relating to soil rights (e.g. height or right of way on the ground), property rights (e.g. encroachment of external insulation on neighboring property) or the appearance of facades or their location
  • Modification of the condition of the exterior parts or of the architectural and decorative elements in contradiction with the rules laid down in remarkable heritage sites classified
  • Building awarded the label Remarkable contemporary architecture

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

The disadvantages of nature technical must be attested by a reasoned note from a construction professional.

The disadvantages of nature economic must be justified by a note drawn up by a construction professional. They may also be justified by a document produced by the contracting authority establishing that the return on investment is greater than 10 years.

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