Buying energy-efficient windows is a 20-year-plus investment — and unfortunately, most quotes on the market compare apples to oranges. Two windows that look identical can differ by 40% in thermal insulation and 100% in longevity. Here is the 7-point checklist we apply ourselves when evaluating a system.
1. The Uw value — the only number that matters
Uw (W/m²K) measures how much heat the complete window loses — frame and glazing together. The lower, the better:
| Uw | Assessment |
|---|---|
| > 2.8 | Old frames without thermal break — an energy sinkhole |
| 1.8 – 2.8 | Basic thermal break — marginally acceptable |
| 1.1 – 1.8 | Good energy performance — the Exoikonomo eligibility threshold |
| ≤ 1.1 | Top-tier performance — SMARTIA/SUPREME territory |
Our projects achieve Uw values as low as 0.9 W/m²K. Always ask for the Uw in writing on the quote — not verbal assurances.
Key Takeaway
Electrostatic Seaside Class coating with reinforced pre-treatment is mandatory for properties within reach of sea air.
2. Thermal break: ask HOW MANY millimetres
"Thermal break" alone doesn't guarantee performance. What matters is the width of the polyamide insulator: a profile with a 20mm polyamide is a world apart from one with 38mm. In the premium systems we install, 38mm polyamides effectively eliminate the thermal bridge.
3. Glazing: 70% of the surface
Energy glazing needs a low-e coating and, ideally, argon gas in the cavity. In the Cretan climate it's also worth discussing solar-control glass on south-facing openings, blocking summer heat gain without sacrificing daylight.
4. Acoustic insulation — experience the 45dB difference
A properly built energy window with the right glazing achieves sound reduction of up to Rw 45dB. In practice: a busy street fades to a whisper. If your home faces a main road in Rethymno or the National Road, this is the feature you'll appreciate most.
5. Security: multi-point locking
The window is a burglar's first test. Ask for perimeter multi-point locking mechanisms and check the burglar-resistance class (RC2/RC3). Combined with a certified security entrance door, the home is protected end to end.
6. Seaside Class coating — non-negotiable near the sea
In Crete, a frame without certified seaside-grade treatment means oxidation and peeling paint within a few years. Electrostatic Seaside Class coating with reinforced pre-treatment is mandatory for properties within reach of sea air.
7. Who fabricates it — and who installs it
The best profile on the market is wasted by careless assembly or installation without proper sealing. Choose a certified fabricator (we are authorised Alumil fabricators) with its own production facility — not a reseller of ready-made units — and ask who handles after-sales support.
