Replacing windows is one of the most cost-effective investments you can make in your home. Replacing single glazing with high-performance double glazing delivers an average saving of €150–300 per year in energy costs per property. The cost of replacing a standard window runs to €350–900 per window including installation — depending on the glazing and frame type. If you replace just the glass yourself in an existing frame, you’ll save €100–300 per window. In this article you’ll find everything you need to know about your options, the costs involved and the step-by-step process.
What Does Window Replacement Cost? DIY vs. Professional
Cost Overview per Window (Standard 100 × 120 cm)
| Glazing type | Glass price | Installation cost | Total — professional | Total — DIY (glass only) |
|---|---|---|---|---|
| Single glazing (old) | — | — | — | reference |
| Standard double glazing | €80–150 | €100–200 | €180–350 | €80–150 |
| High-performance double glazing | €100–180 | €120–220 | €220–400 | €100–180 |
| Premium double glazing (Uw ≈ 1.1) | €120–200 | €130–230 | €250–430 | €120–200 |
| Triple glazing | €180–320 | €150–280 | €330–600 | €180–320 |
Please note: The prices above apply to replacing the glass in an existing frame that is still in good condition. Full window replacement (frame + glass + installation) costs more: €400–1,200 per window.
When Is DIY Worth It?
Replacing just the glass in an existing frame is technically achievable for a competent DIYer. Replacing the entire frame including masonry and sealing work is more demanding and requires experience. Allow 2–4 hours per window for a glass-only replacement.
Glazing Types Compared
| Glazing type | U-value (W/m²K) | Energy saving | Sound insulation |
|---|---|---|---|
| Single glazing | 5.8 | None (reference) | Poor |
| Standard double glazing | 2.8 | Moderate | Average |
| High-performance double glazing | 1.8 | Good | Average |
| Premium double glazing (Uw ≈ 1.1) | 1.1 | Very good | Good |
| Triple glazing | 0.5–0.8 | Excellent | Excellent |
| Solar-control glazing | 1.0–1.5 | Good | Good |
Rule of thumb: Premium double glazing with Uw ≈ 1.1 W/m²K is the standard for new build and renovation in most European countries. It offers the best value for money. Triple glazing is worthwhile in very cold climates or where sound insulation is a priority.
Frame Material: uPVC, Timber or Aluminium?
| Material | Frame price (per window) | Lifespan | Maintenance | Insulation value |
|---|---|---|---|---|
| uPVC | €150–350 | 40–50 years | None | Excellent |
| Timber (factory-primed) | €200–450 | 30–40 years (with maintenance) | Painting (every 5–7 years) | Good |
| Aluminium (standard) | €250–500 | 50+ years | None | Moderate (without thermal break) |
| Aluminium (thermally broken) | €350–700 | 50+ years | None | Excellent |
| Timber-aluminium (composite) | €400–800 | 40–50 years | Minimal | Excellent |
uPVC is the most popular choice for renovation. It’s affordable, maintenance-free and well insulating. The downside: some people find the appearance too “plastic”.
Timber gives the most authentic look but requires regular painting (every 5–7 years). For listed buildings, timber is often mandatory.
Aluminium is durable and sleek in design. Always choose thermally broken aluminium — standard aluminium creates cold bridges and insulates poorly.
Grants for Window Replacement
Many European countries offer grants for energy-efficient window upgrades. In the UK, for example, the Great British Insulation Scheme and ECO4 may provide support. Grants typically:
- Apply to certified high-performance glazing (meeting minimum U-value requirements)
- Require installation by a registered installer (DIY not eligible)
- Must be applied for before or after the work, depending on the scheme
- Can improve your property’s Energy Performance Certificate rating by 1–2 grades
Check with your local energy authority or government website for the current grants available in your country or region.
Energy rating benefit: Upgrading from single glazing to high-performance double glazing can improve your property’s energy label by 1–2 grades, increasing its value.
Materials List (Glass Replacement in Existing Frame)
| Material | Quantity | Indicative price |
|---|---|---|
| High-performance double glazing (Uw ≈ 1.1), made to measure | per window | €120–200 |
| Glazing rubber or bead seal | per window | €5–15 |
| Silicone sealant (clear or grey) | 1 tube per window | €5–10 |
| Glazing packers (plastic) | 1 pack | €5–8 |
| Glass suction cups | 1–2 | €10–25 |
| Glass cutter (if required) | 1 | €8–15 |
| Glazing knife / putty knife | 1 | €5–10 |
Step-by-Step Guide: Replacing Glass in an Existing Frame
Step 1 — Measure and order
Measure the existing glazed area precisely (height × width of the daylight opening — the opening in the frame). Order the new glass 4–6 mm smaller on all sides (allowance for thermal expansion). Check whether the frame and glazing rubbers are still in good condition — if worn, order replacements at the same time.
Step 2 — Remove the old glass
Remove the glazing beads or clips (on uPVC frames) with a flat putty knife. Remove the old glazing rubber. Lift the old pane out — use glass suction cups for safe and comfortable handling. Caution: old single glazing is sharp and fragile. Wear protective gloves.
Step 3 — Clean the frame
Remove all remnants of rubber, sealant and dirt from the frame. Check the corner joints of the frame for damage or corrosion (on aluminium frames). Repair if necessary.
Step 4 — Insert glazing packers and rubber
Place glazing packers on the bottom of the frame profile (to prevent the glass from resting directly on aluminium or uPVC). Fit the new glazing rubber in the rebate (the groove in the frame).
Step 5 — Fit the new glass
Bring the new pane into position using suction cups. Position the glass on the packers and check that it sits evenly in the frame. Press the glass gently into the rebate.
Step 6 — Seal and refit the glazing beads
Refit the glazing beads (on uPVC frames) or apply a bead of sealant along the glass. Ensure a neat, continuous seal on the inside. Smooth the sealant with a wet finger or sealant tool. Leave to cure for 24 hours.
Step 7 — Check and finish
Check all joints for completeness. Test the window by opening and closing it. Remove any protective film from the new glass.
Common Mistakes
| Mistake | Consequence | Solution |
|---|---|---|
| Glass ordered too tight | Glass won’t fit or cracks due to thermal expansion | Always allow 4–6 mm clearance on each side |
| No glazing packers | Glass rests on frame, condensation forms | Always use glazing packers |
| Old rubber not replaced | Draught, damp and leaks | Always replace the rubber when changing the glass |
| Lifting glass without suction cups | Glass falls, breaks, danger of injury | Use professional suction cups |
| High-performance glass in a poor frame | Heat loss through frame remains | Check the frame at the same time and replace if needed |
Conclusion
Replacing windows is an investment that pays for itself through energy savings and a higher property value. Premium double glazing with Uw ≈ 1.1 W/m²K is the standard choice for the best value for money. Doing the glass replacement yourself saves €150–400 per window in labour costs. If using a professional installer, check whether you are eligible for any energy efficiency grants.
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