Why does a private installation concern the co-ownership?
Luxembourg co-ownership law does not apply only to dwellings. It also governs office buildings and mixed-use buildings as soon as ownership is divided into lots comprising a private part and a share of the common parts.
The indoor unit is located in an office, but the installation also comprises refrigerant lines, cables, condensate and an outdoor unit.
These elements may pass through a slab, a duct, a façade, a roof or a common room. Where the titles are silent, the ducts and the parts of the pipework of common equipment remain common even when they pass through a private room. A project presented as private may therefore alter the common parts or the external appearance.
The first question is not the brand of the machine, but the complete route of the installation.
Why should one not drill a slab without a study?
A slab contributes to stability and fire resistance. It may contain reinforcement, prestressing cables, networks or reservations.
An improvised drilling may damage a structural element, cut a network or create a fire-compartmentation defect.
One must consult the plans, locate the networks and seek the opinion of a structural engineer where the structure is concerned. If the plans are incomplete, a survey or a scan may be necessary.
The agreement of the co-ownership does not replace the technical validation.
Where to install the outdoor unit?
The unit may be planned on a façade, a roof, a terrace, a courtyard or in a technical location. Each solution has its constraints.
The noise must be assessed for the offices, dwellings and neighbours. The vibrations require suitable supports. The discharge of hot air must not disturb another occupant.
The appliance must remain accessible for maintenance. The external appearance and the municipal rules must be checked.
How to drain the condensate?
Air conditioning produces water. It must be drained towards a designated point, with a slope, a siphon or a pump depending on the configuration.
A discharge onto a façade, a terrace or the pavement may create marks, infiltrations or black ice. A pump adds noise, maintenance and a risk of breakdown.
The route must appear on the plans.
Which other constraints to examine?
The available electrical power must be checked. An accumulation of individual installations may overload a distribution board.
The wall penetrations must preserve the fire and acoustic performance. Ducts and false ceilings are not free spaces.
The existing ventilation must be examined. Air conditioning cools the air but does not necessarily renew it.
Who works on the refrigerant circuit?
Regulation (EU) 2024/573 governs equipment containing fluorinated greenhouse gases. The checks are no longer determined by a simple weight of fluid, but by thresholds expressed in tonnes of CO₂ equivalent, in particular 5, 50 and 500 tonnes, with a specific threshold of 10 tonnes for certain hermetically sealed equipment.
These thresholds in tonnes of CO₂ equivalent must not lead to concluding too quickly that a small installation is out of scope. For the low-global-warming-potential fluids of Annex II, Section 1 (in particular the hydrofluoroolefins, known as HFOs), the regulation also expresses thresholds directly in mass, of the order of 1, 10 and 100 kilograms. Moreover, a derogation covers hermetically sealed equipment that contains less than 3 kilograms of fluorinated gases, a frequent configuration for small appliances. One must therefore check the fluid used and its charge before concluding that there is an exemption.
The leak checks must be carried out by certified natural persons employed by a certified company. Their frequency depends on the CO₂-equivalent charge and the possible presence of a leak-detection system.
New equipment or equipment that has undergone a major transformation is also subject to an acceptance by the competent agents of the Chambre des Métiers. This acceptance must not be confused with the one provided for since 19 September 2025 for heat pumps connected to a water-based heating circuit: the latter excludes appliances that return the heat to the air.
The end-of-works file identifies the company, the fluid, the charge, the certificates and the maintenance.
Which majority must be obtained?
The authorisation given to a co-owner to carry out at their own expense works affecting the common parts or the external appearance, provided that they are in keeping with the intended use of the building, falls to a majority of the votes of all the co-owners.
If this majority is not reached, a new general meeting may decide by a majority of those present or represented. In the event of a refusal, the co-owner may ask the judge for authorisation to carry out the works if these harm neither the soundness nor the aesthetics of the building, and do not disturb the other co-owners.
These three criteria correspond directly to the project's technical checks: structure, external appearance, noise, vibrations and air discharge.
Which authorisation to request?
An entirely indoor installation is not in the same situation as a project passing through a slab or fixing a unit on a façade.
The request to the syndic must include plans, lines, drillings, location of the unit, acoustics, condensate, electrical power and fire measures.
The general meeting must understand the exact structure. A general authorisation "to install air conditioning" is insufficient if the project is not defined.
Depending on the configuration, a municipal authorisation or one relating to classified establishments may be necessary. The authorisation of the co-ownership does not replace the administrative authorisations.
Who brings the request when a tenant occupies the offices?
In an office building, the user of the premises is often a tenant. As against the syndicate, however, it is the co-owner who presents the request and remains responsible for the installation attached to their lot.
The lease must separately settle the financing, the maintenance, the repairs and the fate of the equipment at the end of the tenancy. The co-ownership does not have to arbitrate this contractual division between landlord and tenant.
What to hand over after the works?
The owner hands over the as-built plans, technical data sheets, certificates, maintenance instructions and the references of the drillings.
In an office building, the fit-outs change with the occupants. Without an up-to-date file, each renovation starts again with a costly search.
A final point must be settled at the time of the authorisation rather than at the time of the resale. The law does not fix the fate of private equipment installed on a common part when the lot changes owner. The resolution of the general meeting must therefore specify the conditions of maintenance, reinstatement and liability, and the seller must pass on this resolution together with the lot's documents.
Reference texts
- Regulation (EU) 2024/573 on fluorinated greenhouse gases
- Environment Administration, certifications
- Environment Administration, leak checks
- Law of 10 June 1999 on classified establishments
- Guichet.lu, classified establishments
- Law of 16 May 1975 establishing the statute of co-ownership of built property (Mémorial A No 28 of 23 May 1975), in particular Articles 1, 2, 3 and 16 — point b) of Article 16 (works affecting the common parts or the external appearance) having been supplemented and point d) (transformation of existing equipment) added by the Law of 22 April 1985 (Mémorial A No 22 of 9 May 1985)