You spend thousands of euros on new windows and the fabricator verbally assures you that the window "doesn't let anything through" and "keeps the heat inside". How can you be sure?
The answer does not lie in the craftsman's word of honour, but in two absolutely mandatory legal documents: the CE Marking and the Declaration of Performance (DoP). If your fabricator cannot provide these documents, the sale is considered illegal under European law.
You have seen the letters "CE" (Conformité Européenne) everywhere, from children's toys to electrical appliances. On windows, the CE marking is not just a sticker nor a "brand". It is the manufacturer's responsible declaration that the window fully complies with strict European standards for health, safety and environmental protection.
For a fabricator to have the right to affix the CE mark, it means their workshop is regularly audited, implements a Factory Production Control system (FPC), their machines are calibrated, and their staff follow the extrusion factory's manuals (e.g. Europa, Alumil) to the letter. Self-assessment is not enough - an initial type test by an independent Notified Body and documentation of each batch are required.
The CE marking must appear on a label on the window itself or in the accompanying documents. It shows the Notified Body code, the standard number (EN 14351-1 for windows) and the essential performance characteristics. If you cannot find it anywhere, it is a serious indication that the fabricator is not complying with the law.
The CE is merely the logo. The real substance lies in the Declaration of Performance (DoP). It is a detailed document that must accompany every window - it contains no marketing fluff, only cold, laboratory-verified numbers.
How much wind pressure the window withstands before it begins to deform or fail (class C1–C5). If the window "leaks" air when closed, the air permeability class reveals it. The higher the class (e.g. Class 4), the more airtight it is against wind.
At how much rain pressure (pascals) the window begins letting water inside. Testing is performed in a specialised chamber. The higher the class (e.g. 9A or E1050), the greater the resistance to wind-driven rain. Particularly critical for coastal areas and upper floors.
The precise insulation value - how much heat the window loses per square metre, per degree of temperature difference, per hour (W/m²·K). This figure results from the combination of profile + glazing. Typical values: old aluminium without thermal break ≈ 5.0 vs modern thermal-break ≈ 1.3–1.8 W/m²·K. This value also determines whether you meet the energy target in the "Exoikonomo" programme.
Under European legislation (standard EN 14351-1) fully transposed into Greek law, the sale of windows without CE Marking and Declaration of Performance is strictly prohibited.
If a craftsman tells you "come on, what do you need the paperwork for - I guarantee my work", it means one of two things: either they are an unlicensed amateur (fabricating windows without certification, without quality controls), or they used counterfeit materials (cheap gaskets, poor mechanisms) that would score below average in an official laboratory. Either way, you bear 100% of the risk.
Market surveillance authorities can seize windows during transport or installation if they lack the required documentation. The fabricator faces a heavy fine, but you are left with incomplete work and no legal protection. Proper documentation also protects you in a future resale of the property.
If you are renovating through a subsidised programme ("Exoikonomo"), the Declaration of Performance (DoP) is the holy grail. Without this document, the Energy Inspector cannot issue the 2nd EPC.
The chain is clear: 1st EPC → Acceptance → Window installation → DoP with U-value → Energy Inspector verifies → 2nd EPC → Disbursement. If the DoP is missing, the chain breaks at the most critical point - the Inspector has no legal proof of the insulation coefficient achieved. Result: your application is rejected and you lose the entire subsidy.
On the day you take delivery of your new windows and before paying the fabricator in full, request together with the invoice: the CE label (affixed to the window), the Declaration of Performance (DoP) in paper or PDF, and the Recycling Certificate if you are in "Exoikonomo". These three documents are the only irrefutable proof that you did not buy a "pig in a poke" but a product that is tested, safe and legal.
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