The installation of an external thermal coat has become one of the most adopted solutions to reduce the energy needs of buildings, especially existing ones, and improve internal comfort.
Precisely because it is a very widespread intervention today, however, it is often treated as a standard operation: the material, the thickness is chosen, the transmittance is checked, a stratigraphy is attached to Law 10 and then the rest is left to the construction site. Here lies the main misunderstanding: delegating.
A coat is not a product, it is a system. It only really works when it’s designed in its entirety: materials, details, knots, compatibility, pose and controls. Thinking that “the design of the coat” ends in the calculation of the transmittance means ignoring precisely what determines quality and durability over time: the executive design of the facade details.
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A coat is not a panel: it is a certified ETICS system
From a technical point of view, the external insulation falls within the ETICS systems (External Thermal Insulation Composite Systems), regulated at European level by specific evaluation documents.
From 2021, the ETAG 004 guideline has been replaced by the regulatory reference EAD 040083-00-0404, the basis for issuing ETA (European Technical Assessment) certifications. This step is fundamental: it means that a coat cannot be understood as “insulation + smoothing”, but as a set of components tested and certified as a single system.
An excellent ETICS is composed of at least:
- glue and/or mechanical fixing, to transfer loads to the support (own weight and wind action);
- insulating material, responsible not only for reducing dispersions but also for summer behavior;
- base plaster with reinforcement mesh, necessary to absorb surface tensions and mechanical stresses;
- finishing plaster, which protects from atmospheric agents (rain, UV) and guarantees durability.
The final performance therefore depends on the coherence of the entire package, not just on the conductivity value of the insulation.
The real problem: delegating everything to the installation
Recent technical news – construction sites, disputes and building pathologies – clearly shows one point: many critical issues arise when the installation is completely delegated to the installers, often without an executive plan to guide choices and sequences.
But the problem arises even earlier: the diagnosis of existing support is often absent. Preliminary tests are essential to understand the reliability of the bonding surface, as well as assessing the flatness of the facade, which may present irregularities between the top and the base.
Correct adhesion of insulating panels requires a surface:
- resistant,
- consistent,
- free of contamination,
- dry and stable.
The Cortexa technical manual, for example, dedicates ample space to verifying the suitability of the surface, highlighting possible critical issues:
- impurities and inconsistent layers;
- friable or chalky surfaces;
- lack of adhesion between plaster and masonry;
- serious irregularities or walls out of plumb;
- presence of cracks (due to settlement, movement or structural);
- saline efflorescences;
- biological infestations (algae, mold).
In the presence of defects, specific preparation operations are necessary, which constitute an integral part of the ETICS application technique.
The presence of rising humidity from the ground, infiltration from cracks or leaky joints also represents a critical condition: insulating a damp wall often means masking the problem and increasing the risk of deterioration over time.
Likewise, a coat does not fail “in the middle of the wall”, but in the details:
- plinths and ground connection,
- balconies and terraces,
- intrados and under-pallets,
- roller shutter guides,
- windowsills and overhangs,
- plant crossings,
- ventilation grills and fixings.
It is these connections that determine the continuity of the insulation and the prevention of thermal bridges and pathologies.
Laying boards: what they are and why they make the difference
Correct design is based above all on the study of detail. Details that must be thought out, resolved, drawn in graphic documents that serve as a guide for installers on the construction site.
A well-made laying board:
- identifies all the critical points of the facade,
- defines system components and layering,
- specifies tapes, profiles, seals and fittings,
- clarifies reinforcements and corner protectors,
- describes the tessellation (type and spacing).
In practice, it translates into a “constructible way” what otherwise remains theory.
Conclusion: the perfect coat is not born on the facade, it is born before
If we want to take a step forward in construction quality and durability, we must put a simple concept back at the center: the coat is designed before installing it. Energy performance is not just a number in Law 10. It is continuity, detail, component compatibility, installation sequence, checks and verification.
A coat can and must be installed perfectly, but a guide is needed: a detailed executive project that transforms the facade into a legible, constructible and verifiable system. Only in this way does the performance become real, repeatable and durable over time.
