Oikodomisis

CE Marking & Declaration of Performance (DoP): Your Window's "Identity Card"

Imagine buying a car with no technical specs - no fuel economy, no horsepower, no safety ratings. That's exactly what happens when you buy windows without CE Marking and a Declaration of Performance (DoP).

The CE mark is not just another "bureaucratic stamp." It's the legal guarantee that the performances promised by the seller correspond to real, verifiable laboratory tests. In Greece, the vast majority of consumers never ask for it - and it costs them dearly.

1. What Is CE Marking for Windows?

The CE mark (Conformité Européenne) declares that the product complies with the European Construction Products Regulation (CPR – 305/2011) and the harmonised standard EN 14351-1 for windows and external doors. Under Greek and EU law, no window can be legally sold within the EU without CE marking. In practice, many small fabricators in Greece sell without CE - this is illegal and leaves the consumer without any real protection.

CE marking on an aluminium window - legal requirement

⚖️ Why Is It Mandatory?

It protects the consumer. It ensures the manufacturer or importer has tested the windows at an accredited laboratory (notified body) and publicly declares their performance. If it doesn't carry CE, you literally don't know what you're buying. Nobody can guarantee how much air gets through, how much rain it stops, or whether it can handle wind pressure. Furthermore, in case of a defective product, CE + DoP serve as a legal weapon in your hands for compensation or replacement.

2. The Declaration of Performance (DoP): Your Window's "Health Booklet"

Declaration of Performance DoP - fields: Uw, airtightness, watertightness

The DoP is a legal document that must accompany every CE-marked window. The manufacturer is legally bound to the declared values.

📋 What Does the DoP List?

Thermal transmittance (Uw): e.g. Uw = 1.4 W/m²K
Air permeability: e.g. Class 4
Watertightness: e.g. 9A or E750
Wind resistance: e.g. C4
Sound insulation (Rw): e.g. 38 dB
Each value corresponds to a laboratory test that can theoretically be re-verified at any time.

❓ What Does "npd" Mean?

npd = No Performance Determined. If you see npd next to "Air permeability", it means the property was never tested. The manufacturer makes no commitment. This should worry you: a window with untested airtightness most likely doesn't even achieve Class 2 - meaning it leaks badly.

3. Buyer's Checklist: 5 Things You Must Verify

Before signing any quote, make sure your supplier can provide:

Buyer checklist for window purchase - CE, DoP, npd

1️⃣ DoP Sample

Request a copy of the Declaration of Performance before placing your order. If they can't provide one, think very carefully before proceeding.

2️⃣ No "npd" Lines

Check that no essential characteristic (Uw, air permeability, watertightness, wind resistance) is listed as npd. If it is, ask "why?"

3️⃣ Classes ≥ 4 / 7A / C3

For Greek conditions: airtightness Class 4, watertightness 7A+, wind resistance C3+. This ensures a window suitable for at least 20 years of operation.

4️⃣ Uw ≤ 1.8 W/m²K (or lower)

KENAK requires Uw ≤ 2.0 generally, but for EPC class B+ target ≤ 1.5. For passive houses, aim for ≤ 1.0.

5️⃣ Notified Body Number

The CE label must show the four-digit number of the laboratory that performed the tests. This means the results can be independently verified.

4. How Does the DoP Save You Money?

The DoP is more than just "paperwork." Documented performance means you're not paying blindly: you know exactly what you're getting.

Cost savings from choosing DoP-certified windows

💰 "Exoikonomo" Subsidy

Most energy-upgrade subsidy programmes in Greece explicitly require DoP/CE. Without them, you won't qualify for the subsidy - even if you installed excellent windows.

📈 Higher Property Value

A property with documented energy-efficient windows (DoP + high EPC) sells for 10–15% more according to European studies. The DoP proves the performance - the seller's word alone isn't enough. Moreover, with the DoP in hand you can objectively compare quotes from different suppliers: you're no longer comparing just "prices" but performance and price together - just as you would with any other serious purchase.

Related Articles

Window Airtightness (Classes 1–4): Why Your Home Leaks Air Window Watertightness (Classes 1A–9A): Drainage Slots & Weep Holes Test Chambers: Window Certification in the Laboratory Blower Door Test: Whole-House Airtightness Check

Preview