What is the difference between single glazing, double glazing, HR++ and HR+++ (triple glazing)? Compare insulation values, costs per m², payback periods and which ISDE subsidies you can apply for.
| Glass type | U-value | Thickness | Glass only (per m²) | Incl. installation (per m²) | ISDE subsidy |
|---|---|---|---|---|---|
| Single glazing | 5.8 W/m²K | 4 mm | €20 – €35 | €50 – €80 | ❌ None |
| Standard double glazing | 2.8 – 3.2 W/m²K | 24 mm | €45 – €70 | €80 – €130 | ❌ None |
| HR++ glass | 1.0 – 1.2 W/m²K | 28 mm | €70 – €110 | €110 – €180 | ✅ ~€27–€35/m² |
| HR+++ / triple glazing | 0.5 – 0.7 W/m²K | 40–44 mm | €110 – €180 | €160 – €260 | ✅ ~€40–€52/m² |
U-value: the lower, the better insulated. Dutch Building Decree 2026 requires max. 1.65 W/m²K when replacing glazing.
The U-value (thermal transmittance coefficient) indicates how much heat is lost per m² of glass for each degree of temperature difference. As an illustration for a home with 15 m² of glass:
Outdated; no longer meets building regulations. Feels cold, draughty, condensation on glass. Combined with a gas boiler, extremely energy-wasteful.
Standard in homes built after 1980. Does not meet current standards when replacing glazing. Limited insulation compared to HR++.
Current standard. Argon gas + low-e coating. Required when replacing frames (Building Decree). Best value for money for most homes.
Three glass panes, two cavities. Heavier, more expensive, but optimal insulation. Worthwhile when renovating to label A++ or in combination with a heat pump.
Choosing more sustainable glass has direct consequences for the rest of the renovation:
| Consideration | HR++ glass | HR+++ / triple glazing |
|---|---|---|
| Frame depth required | Minimum 28 mm | Minimum 40 mm — older frames often too shallow |
| Weight per m² | ~15–18 kg/m² | ~25–35 kg/m² — extra sturdy hinges required |
| Replace frames too? | Often not necessary if frame is in good condition | Often necessary (depth + weight) |
| Adjust ventilation | Recommended (improved airtightness) | Required — mechanical ventilation or HRV recommended |
| Condensation risk | Minimal | Possible external condensation (outside of glass) — normal phenomenon |
| Sound reduction | Rw ≈ 32–35 dB | Rw ≈ 36–42 dB — additional sound insulation |
Through the ISDE scheme (Investment Subsidy for Sustainable Energy and Energy Savings) you can apply for subsidies for insulation measures, including HR++ and HR+++ glass. Here is how it works:
You have two options when replacing glass:
Cheapest option if the frame is in good condition and deep enough (min. 28 mm for HR++). A glazing company removes the old glass and installs new insulating glass.
Necessary with rotten wood, frames that are too shallow or too tight, or when upgrading to triple glazing. Including ISDE subsidy and energy savings, the most attractive long-term investment.
| Scenario | Annual savings | Investment (excl. subsidy) | Payback period |
|---|---|---|---|
| Single → HR++ (glass only, 15 m²) | approx. €350 – €500/year | approx. €1,500 – €2,500 | 4–6 years |
| Single → HR++ (frame + glass, 15 m²) | approx. €350 – €500/year | approx. €4,000 – €8,000 | 10–16 years |
| Double → HR++ (reglazing, 15 m²) | approx. €150 – €250/year | approx. €900 – €1,800 | 5–8 years |
| HR++ → HR+++ (triple, 15 m²) | approx. €50 – €100/year | approx. €750 – €1,500 additional cost | 10–20 years |
Savings depend on gas consumption, property type and heating habits. Based on a gas price of €1.40/m³.
HR++ glass has a U-value of approximately 1.1 W/m²K and consists of two glass panes with a cavity filled with argon gas and a low-emissivity coating. HR+++ (triple glazing) has three glass panes, two cavities and a U-value of 0.5–0.7 W/m²K — making it more than twice as insulating as HR++. Triple glazing does cost 40–60% more than HR++ and is heavier, which places additional demands on window frames.
You can, but there are limitations. Replacing only the glass (reglazing) is cheaper than installing entirely new frames. Requirements: the existing frame must be in good condition, deep enough for the new glass thickness (HR++ requires at least 28 mm frame depth, triple at least 40 mm), and properly sealed. Reglazing costs €80–€180 per m² (glass + labour only), versus €350–€1,500 per frame for full replacement.
Through the ISDE subsidy (Investment Subsidy for Sustainable Energy and Energy Savings) you can apply for subsidies for insulation measures including HR++ and HR+++ glass. In 2025–2026 the subsidy for glass is approximately €27–€35 per m² for HR++ and €40–€52 per m² for triple glazing. Applications are submitted via RVO.nl and must be filed within 24 months of the investment.
A home with single glazing that is upgraded to HR++ glass saves approximately €200–€450 per year on energy costs (depending on surface area and heating habits). The additional investment compared to double glazing (averaging €500–€1,500 per frame including labour) pays for itself in 4–8 years. With the ISDE subsidy, the payback period is 3–6 years.
Glass has a significant impact on the energy label. A home with single glazing typically scores energy label E or F. Upgrading to HR++ glass can improve the label by 1–2 steps (e.g. from E to C). Triple glazing (HR+++) can yield an additional label improvement. A higher energy label increases property value: label C vs. E delivers on average €10,000–€25,000 more at sale.
Triple glazing has three drawbacks: it is heavier (25–35 kg/m² vs. 15–18 kg/m² for HR++), requiring sturdier frames and hinges; it is more expensive (40–60% more than HR++); and it slightly reduces solar heat gain (g-value), which is beneficial in summer but means somewhat less passive solar warmth in winter. In well-insulated homes (nearly energy-neutral), the additional benefit over HR++ is often marginal.
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