When undertaking a home renovation, attention often focuses on finishes, space distribution, and energy efficiency. An equally important but often underestimated aspect concerns the technical documentation of the systems.
Certifications represent proof that the systems have been built according to current regulations and comply with the safety requirements provided by law.
This is not a mere bureaucratic formality. Certifications affect the safety of the property, its marketability, the ability to obtain permits, and the protection of the owner in the event of accidents or disputes.
System certifications: what they are and what function they perform
In common parlance, people often speak of “system certification,” but the main document required by Italian law is the Declaration of Conformity (Di.Co.), governed by Ministerial Decree 37/2008.
Upon completion of the work, the licensed installation company must issue a declaration to the client certifying that the system has been built to the highest standards, in compliance with applicable technical standards and the safety requirements provided by law.
The documentation normally includes:
· declaration of conformity;
· system design project, when required;
· diagram of the installed system;
· list of materials used;
· documentation relating to the installation company.
Certifications attest that the system has been designed and built according to applicable regulatory requirements, verifying its compliance with the required safety standards.
Reference regulations in 2026
The main regulation remains Ministerial Decree 37/2008, updated over the years to adapt to technological evolution and the new system requirements of buildings. The decree regulates the design, installation, transformation, expansion, and maintenance of systems serving buildings.
The fundamental principle is clear: systems must be built by licensed companies and must be accompanied by documentation certifying their conformity with current technical standards.
The lack of documentation can create problems during the sale process, requests for certificates of occupancy, building permits, and subsequent maintenance or expansion work.
Quali impianti devono essere certificati
The obligation applies to various categories of systems installed in residential and commercial buildings:
Declaration of conformity for the electrical system
The electrical system is probably the best-known case. The electrical system declaration of conformity is issued after the installation of a new system or following interventions that substantially modify its characteristics and functionality.
The documentation certifies that the system has been built according to applicable CEI standards and that it meets the safety requirements provided by the regulations.
The conformity of electrical systems takes on particular importance in full renovations, when switchboards, lines, protections, and safety devices are replaced.
Gas system certification
Systems intended for the distribution and use of gas must also be accompanied by specific conformity documentation.
Gas system certification is fundamental because it concerns systems that, in the event of defects or incorrect installations, can involve very high risks, such as gas leaks, fires, or explosions.
For this reason, the regulations impose rigorous checks and the issuance of documentation by licensed companies.
Plumbing and sanitary systems
The obligation also includes domestic water distribution systems, drains, and plumbing networks within buildings.
During a complete renovation of the bathroom or kitchen, interventions involving the replacement of the networks normally require the issuance of a declaration of conformity for the work performed.
Heating and air conditioning systems
Boilers, heat pumps, air conditioning systems, and centralized or independent heating systems are subject to the provisions of Ministerial Decree 37/2008.
Certification also takes on particular importance for energy efficiency and the correct management of systems over time. Furthermore, when the interventions qualify for tax incentives, such as the Ecobonus, the technical documentation of the systems may be necessary to access the deductions.
Photovoltaic system certification
Certification of photovoltaic systems is necessary to attest to the correct installation of the system, compliance with applicable technical standards, and the safety of the connection to the building’s electrical grid.
The documentation is also indispensable for many administrative, insurance, and grid connection procedures.
When certification is mandatory during a renovation
One of the most frequent questions concerns when it is necessary to obtain the documentation.
Generally speaking, the declaration of conformity is mandatory when a new system is installed or when interventions are carried out that significantly modify its structure, operation, or technical characteristics.
Common cases include:
· complete rewiring of the electrical system;
· full replacement of the gas system;
· installation of a new air conditioning system;
· installation of a heat pump;
· installation of a photovoltaic system;
· significant expansions of existing systems;
· transformations involving substantial changes to the original configuration.
Upon completion of the work, the contractor must deliver the documentation to the owner or the client.
What happens if the certification is missing
The absence of documentation does not automatically mean that the system is dangerous, but it creates a situation of technical and legal uncertainty.
In the event of a property sale, the buyer may request information on the available documentation. Furthermore, the absence of certifications can complicate subsequent interventions, building permits, and insurance claims.
When the original declaration is not available and the conditions provided by the regulations are met, it may be possible to use a Declaration of Suitability (Di.Ri.), a tool that can be used for certain categories of systems built in specific historical periods and subjected to technical verification by qualified professionals.
Certified systems: added value for the property
The presence of certified systems is not just a regulatory requirement.
For the owner, it means being able to demonstrate that the systems were built by qualified operators and according to the required technical standards. For a potential buyer, it constitutes an additional guarantee of the quality of the property.
In a real estate market increasingly attentive to technical and energy aspects, the availability of complete documentation can help simplify a sale and reduce the risk of future disputes.
Why you should always keep system documentation
One of the most common mistakes is losing or failing to correctly archive the documentation received at the end of the work.
Certifications should be kept together with the other technical documents of the property, such as building permits, energy certifications, and maintenance manuals.
Having the documentation readily available can be essential in the event of subsequent renovations, requests from the Municipality, insurance procedures, rentals, or sales.
