Secondary Glazing Cost Guide (2026)
A transparent, specifier-focused breakdown of secondary glazing prices across London and the Home Counties. All figures are supplied and installed, inclusive of survey and VAT at the 5% energy-saving-materials rate where applicable.
Per-window installed price ranges
| Configuration | Glass | Typical size | Installed price |
|---|---|---|---|
| Fixed panel | 4mm float | ≤1.0m² | £450–£650 |
| Fixed lift-out | 6.4mm laminate | 1.0–1.5m² | £550–£800 |
| Horizontal slider (2-pane) | 4mm float low-e | 1.2–1.8m² | £650–£950 |
| Vertical slider (sash) | 6.4mm laminate | 1.0–1.6m² | £750–£1,100 |
| Vertical slider — acoustic | 10.8mm Stadip Silence | 1.0–1.6m² | £950–£1,400 |
| Casement (side-hung) | 6.4mm laminate | ≤1.2m² | £650–£950 |
| Bay window (per facet) | 6.4mm laminate | 0.8–1.2m² | £700–£1,100 |
Whole-property price bands
| Property type | Openings | Standard spec | Acoustic spec |
|---|---|---|---|
| 1-bed flat | 4–6 | £2,600–£4,800 | £4,200–£7,200 |
| 2-bed terrace | 6–10 | £4,200–£8,500 | £6,800–£12,500 |
| 3-bed Victorian house | 10–14 | £6,500–£12,500 | £10,500–£18,500 |
| 4-bed Edwardian house | 14–20 | £10,500–£18,500 | £16,000–£28,000 |
| Listed townhouse (Grade II) | 16–24 | £14,000–£24,000 | £22,000–£36,000 |
What drives the price?
- Glass specification (30–45% of unit cost): 10.8mm Stadip Silence is 3.2× the price of 4mm float per m².
- Frame finish (10–15%): mill anodised is cheapest; RAL / Farrow & Ball colour-match adds £45–£90 per unit.
- Opening type (15–25%): vertical sliders on spiral springs are the most complex; fixed panels are cheapest.
- Access & scaffolding (5–20%): upper-floor bay windows requiring external scaffold access add £600–£1,800 to a project.
- Survey and installation (fixed): £180 survey (refunded on order), 1–2 days installation per 10 openings.
Payback and ROI
Typical measured energy savings on a 3-bed Victorian terrace with untreated single glazing: £340–£520/yr at 2026 Ofgem cap prices. Payback on a £8,500 project therefore lands in the 16–25 year range — but the acoustic and comfort benefits deliver value on day one, and DCLG research shows a 1.5–3% property-value uplift on heritage properties fitted with secondary glazing.
VAT and grants
- 5% VAT under HMRC Notice 708/6 for domestic energy-saving materials (until 31 March 2027).
- ECO4 flex funding available in eligible boroughs — see our Compliance Hub.
- Listed building repair works may qualify for zero-rating; we advise a specialist VAT consultant.
Secondary glazing cost FAQs
How much does secondary glazing cost per window in London (2026)?
Typical London installed prices range from £450 for a small fixed panel with 4mm float glass to £1,400 for a large vertical-sliding sash unit with 10.8mm acoustic laminated glass. Most three-bed terraces fall between £4,500 and £9,500 for a whole-house install.
Is secondary glazing cheaper than replacement double glazing?
For heritage or listed windows, yes — typically 40–60% cheaper. Replacement sash windows cost £2,200–£4,500 per opening; secondary glazing achieves comparable thermal performance at £550–£1,100 while preserving the primary window.
What drives the price difference between quotes?
Four variables dominate: glass specification (4mm float vs 10.8mm acoustic laminate can double the price), frame finish (mill anodised vs RAL powder-coat), opening type (fixed vs vertical slider), and access (ground floor vs upper-floor with scaffolding).
Are there any VAT reductions available?
Secondary glazing installed as an energy-saving material in a residential dwelling qualifies for the reduced 5% VAT rate under HMRC Notice 708/6 until March 2027. Commercial installations remain at 20%. Listed building repairs may qualify for zero-rating under specific conditions.
How much does a whole-house secondary glazing project cost?
Budget £2,600–£4,800 for a 1-bed flat (4–6 openings), £6,500–£12,500 for a 3-bed Victorian house (10–14 openings) on standard specification, and £10,500–£18,500 for the same property on a 10.8mm acoustic specification.
What is the payback period on secondary glazing?
Measured savings on a 3-bed Victorian terrace with untreated single glazing are £340–£520 per year at 2026 Ofgem cap prices, giving a 16–25 year simple payback on an £8,500 project — alongside immediate acoustic, draught and comfort gains and a 1.5–3% heritage property value uplift.
Client reviews on pricing and value
Rated 5.0 out of 5 from 3 client reviews across London.
"Absolutely fantastic service! The secondary glazing has transformed our Victorian home. The noise reduction is incredible — we can barely hear the traffic from the main road now. The installation was professional and clean, and the team respected our period features perfectly."
Sarah Johnson
Kensington, London
"Outstanding results for our office building. The secondary glazing has significantly improved our working environment — much quieter and more comfortable temperature control. The project was completed on schedule and within budget. Highly recommended for commercial properties."
Michael Chen
Canary Wharf, London
"We were sceptical about adding glazing to our listed building, but the team provided a solution that satisfied both conservation requirements and our comfort needs. The reduction in condensation and draughts has been remarkable. Professional service from start to finish."
Emma Thompson
Hampstead, London