Secondary glazing is an English Heritage approved solution for listed & period properties.
Secondary glazing is an English Heritage approved solution for listed & period properties.
The UK's most accurate secondary glazing cost calculator. Enter your window size, style and glass for a live itemised price, dB noise reduction and annual heating saving. Low profile aluminium with Saint-Gobain acoustic glass, fitted across London & the UK — and recommended by English Heritage for listed buildings. We beat any like for like quote.
Your secondary glazing cost updates live on the right — fully itemised, with the expected noise reduction and heating saving. No sign-up, no waiting.
Replacing original heritage timber windows typically costs 3.5–5× more than secondary glazing — and you lose the original windows in the process. A well-specified secondary glazing system also outperforms replacement double glazing on acoustics: its wider air gap blocks far more noise than the slim cavity of a sealed unit. You keep your heritage windows, pay a fraction of the price, and get a quieter, warmer home.
Measure the visible opening in millimetres — width left-to-right and height top-to-sill — then enter the largest reading for an accurate secondary glazing cost. If anything's awkward, our surveyor takes the measurements for you on the free site visit.
Measure the visible opening in millimetres. For old or distorted frames, take top and bottom widths and use the largest.
Measure from the inside top of the frame to the inside sill in millimetres. Take both sides and use the largest.
Pick the closest matching style and the glass that suits your priority — acoustic, thermal or both. We'll confirm everything on survey.
Secondary glazing cost is worked out per square metre, based on the window style you choose and the glass specification — then a small per-window charge applies for a custom colour finish. Our calculator uses the exact same real m² rates below, so the price you see is the price we quote.
Because we use a slim, low-profile aluminium system manufactured in the UK, we keep costs down and beat any like-for-like quote — while fitting discreetly into listed and period properties with no alteration to your original windows.
The main drivers are window size (priced per m², with a 0.5 m² minimum per unit), the opening style (sliding sash, horizontal slider, lift-out or hinged casement), the glass (standard toughened vs 6.4mm Saint-Gobain Stadip Silence acoustic laminated) and the frame finish (standard white or a custom RAL colour). Order multiple windows together and a volume discount is applied automatically.
| Window style | From (per m²) |
|---|---|
| Lift-out Panel · fixed | £291 |
| Horizontal Slider | £353 |
| Vertical Sliding Sash | £439 |
| Casement · hinged | £460 |
| 6.4mm Acoustic Laminated glass | +£72 |
| Custom RAL colour | +£174 / window |
The calculator gives an accurate guide price for a standard installation, but every property is different — so location, logistics and the scope of any additional works can cause the final figure to vary. Common reasons a job can cost more than the online estimate include:
Everything you need to know before you get your quote.
Secondary glazing cost is priced by square metre based on the window style and glass. Low-profile aluminium starts from around £291/m² for a fixed lift-out panel, £353/m² for a horizontal slider, £439/m² for a vertical sliding sash and £460/m² for a hinged casement — plus an optional +£72/m² for 6.4mm Saint-Gobain Stadip Silence acoustic laminated glass and +£174 per window for a custom RAL colour. Use the calculator above for an instant itemised quote.
Per-window cost = charged area (m²) × (style price per m² + glass surcharge per m²) + any frame surcharge. A minimum charged area of 0.5 m² applies to small windows. Order more than one window and a multi-window discount of 1% per additional window is applied automatically, capped at 50%.
With 6.4mm Saint-Gobain Stadip Silence acoustic laminated glass and our low-profile aluminium system, customers typically see around a 30 dB Rw reduction — roughly 55% of audible street and traffic noise blocked compared with a single-pane window. A wider air gap increases the effect further.
On average our customers save around £68 per window per year on heating and report rooms feeling 3–5 °C warmer. The exact saving depends on the condition of the existing window, room size and energy prices.
Yes. Low-profile aluminium secondary glazing is fitted internally behind the existing window with no alteration to the original frame, so it is conservation-officer friendly and widely accepted in Grade I and Grade II listed buildings and conservation areas.
Yes — English Heritage recognises secondary glazing as one of the most effective and least intrusive ways to improve the thermal and acoustic performance of windows in historic and listed buildings. Because it is fully reversible and leaves the original window untouched, it is the preferred option in listed buildings and conservation areas where replacement double glazing would not be permitted.