The glazing is the largest surface of your window — and the most exposed to losses. High-efficiency double glazing (HR++) divides losses by four versus single glazing, improves acoustic comfort and reduces condensation. The first investment to consider, even before choosing the frame.
The numbers that matter for quality glazing, fitted by our teams. Concrete benchmarks to understand the Ug values, the gas and the spacer.
The Ug coefficient measures losses through the glazing alone. An HR++ double drops to 1.0 W/m²K thanks to the low-emissivity coating and the argon fill — four times better than single glazing.
The gap between the two panes is filled with argon (or krypton on premium units), an inert gas less conductive than air. It accounts for most of the thermal gain over an old double glazing.
An invisible metallic deposit on the inner face of the glazing reflects heat back inside in winter and limits overheating in summer. Without this coating, double glazing loses half its efficiency.
Asymmetric double glazing (panes of different thicknesses) reaches a sound reduction of 35 to 40 dB — enough to markedly cut the noise of a busy street or a railway line.
The composite warm-edge spacer replaces aluminium between the panes. The result: less edge condensation, better comfort and an improved overall Uw value.
Properly fitted double glazing keeps its seal and argon fill for 20 to 25 years. After that, the gas escapes and performance declines — a sign it is time to renovate.
* Indicative values for standard-range HR++ double glazing. Exact performance depends on the thickness, gas and spacer — confirmed at the survey.
HR++ double glazing is the standard in Belgium, but it is not always the only option. Here is when it excels and when triple glazing takes over.
In the majority of Belgian renovations, HR++ double glazing is the rational choice. A few cases where it stands out:
Moving from single glazing or 1990s double glazing to a modern HR++: the thermal gain is immediate and the budget stays under control.
When many openings have to be changed, HR++ double glazing offers the best insulation-to-price ratio across the whole house.
Double glazing lets through more solar heat than triple: an advantage on sunny façades where you want to enjoy the free gain.
On a north façade, in a low-energy build or if the budget allows, triple glazing drops to Ug ~0.5 W/m²K. We compare both options at the survey and tell you straight which is worth the extra cost for each opening. Combine with the right PVC window or aluminium for a coherent whole.
A 1970s house still on single glazing, cold in winter with condensation on every window. We fitted HR++ argon double glazing with a warm-edge spacer on 12 openings, in the new PVC windows. The result: no more draughts, no more condensation, and a lighter heating bill.
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« Nous avons fait appel à la société Wendows pour le renouvellement de nos châssis et nous sommes vraiment ravis du résultat ! Les travaux ont été réalisés dans les délais annoncés et la finition est impeccable. De plus, M. Aprile qui s'est occupé du devis, s'est toujours montré disponible pour répondre à toutes nos questions. Nous vous recommandons donc de faire appel à eux pour vos travaux ! »
« Nous avons fait appel à Wendows pour le remplacement de nos châssis et nous sommes très satisfait de notre choix. Qualité et suivi de chantier au top ! »
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The choice of glazing weighs more than the frame on performance. Compare the options to see which one is the right fit for your home.
| Critère | HR++ doubleVous êtes ici | Triple glazingVoir la gamme → | Acoustic doubleVoir la gamme → |
|---|---|---|---|
| Thermal insulation (Ug) | 1.0–1.1 W/m²K | 0.5–0.7 W/m²K | 1.0–1.1 W/m²K |
| Acoustic insulation | 32–35 dB | 33–36 dB | 38–42 dB |
| Solar gain (g) | Good | Lower | Good |
| Price | The gentlest | 15–25% more | 10–20% more |
| Weight | Standard | Heavier | Heavier |
| Ideal for | Renovation, set budget | New build, low energy, north | Noisy street, airport |
The most-fitted frame with HR++ double glazing. The best insulation-to-price ratio for the whole window.
See PVC →Slim profiles for large glazed surfaces: aluminium shows off double glazing on XXL bays.
See aluminium →Warmth of wood inside, maintenance-free aluminium outside. The premium choice with double or triple glazing.
See wood-aluminium →Limit summer overheating and gain night-time comfort with exterior shutters or screens.
See the shutters →Fitted price ranges by frame and type of glazing, grants and 6% VAT included.
See the prices →An overview of our windows & joinery in Belgium: materials, glazing, fitting and grants on one page.
Back to the windows guide →The price depends on the type of glazing, the size of the opening and the associated frame. Here are benchmarks for double glazing fitted in a new frame.
See the window & glazing price list →* Indicative ranges for HR++ double glazing fitted in a new frame. Price of the glazing alone (replacement in an existing frame): on quote. A costed estimate is provided with your free quote.
A 1990s double glazing has a Ug of around 2.8 W/m²K. A modern HR++ drops to 1.0 thanks to the low-emissivity coating and the argon gas — almost three times better. If your windows are more than 20 years old, replacing them divides the losses through the glazing.
HR++ double is enough in most Belgian renovations. Triple glazing makes full sense in a low-energy new build, on a very exposed north façade or if your budget allows. We compare the Ug values and the extra cost for each opening.
Ug (g for “glass”) measures the amount of heat that passes through the glazing alone, in W/m²K. The lower it is, the better the glazing insulates. As the glazing represents about 70% of a window’s surface, it is the value that weighs most in the overall performance (Uw).
Yes, especially in its asymmetric acoustic version (panes of different thicknesses, laminated). Acoustic double glazing reaches 38 to 42 dB of sound reduction, against 32 to 35 for a standard HR++. We recommend the acoustic version along roads and railways.
Sometimes, if the frame is in good condition and accepts the thickness of modern glazing. In practice, old frames often have profiles that are too narrow or worn seals: replacing the whole unit is more reliable and qualifies for grants.
Grants are based on the performance of the whole unit (window + glazing, Uw coefficient). A new frame with HR++ double qualifies for renovation grants (up to 35% depending on income) and 6% VAT for homes over ten years old. We handle the paperwork for you.
Free on-site survey, double/triple comparison per opening, grants calculated. Describe your project in under a minute.