Listed Buildings · Conservation Areas · Period Homes
Secondary Glazing in London & Hertfordshire
Bespoke, discreet secondary glazing systems that preserve original windows while reducing heat loss by up to 75% and external noise by up to 80%. Sympathetic solutions for Grade I, Grade II* and Grade II listed properties across the capital.
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What is secondary glazing?
A discreet inner window that does the hard work
Secondary glazing is a fully independent internal window system fitted to the room side of your existing windows. It creates a sealed pocket of air that insulates against heat loss and noise, while leaving the original window fabric completely untouched. For period properties and homes in conservation areas, it is the ideal way to gain modern thermal and acoustic insulation without sacrificing original sash windows.
Because it is reversible and planning-friendly, secondary glazing is Historic England's preferred solution for upgrading historic windows. It delivers genuine improvements in thermal insulation, noise reduction and comfort across listed buildings and period homes, with none of the consent headaches that come with full replacement.
The benefits
Why homeowners choose secondary glazing
All the comfort of modern glazing, with none of the disruption to your original windows.
Up to 75% less heat loss
A sealed internal air gap dramatically cuts the heat escaping through original windows.
Up to 80% noise reduction
Acoustic glass and a wide cavity reduce external noise by up to 54dB for a calmer home.
No planning permission usually required
As an internal, reversible system it rarely needs planning consent — ideal for protected homes.
Preserves original windows
Your historic sashes and frames stay untouched, avoiding listed-building consent issues in most cases.
Less condensation & draughts
A warmer inner pane and sealed cavity reduce misting, damp and cold draughts.
Fully reversible
Secondary glazing can be removed entirely with no permanent alteration to the building fabric.
System options
A system to suit every window
Every installation is made to measure and matched to the operation of your existing windows.
Vertical Sliding Sash
Slides up and down to mirror the proportions and operation of traditional box sash windows. The discreet choice for period homes.
Horizontal Sliding
Panels glide side to side, perfect for casement and modern windows where easy daily access is needed.
Side-Hung Casement
Hinged panels open fully inward for unrestricted access to the original window, cleaning and ventilation.
Lift-Out / Fixed Panels
Removable or fixed units for rarely-opened windows, giving the slimmest sightlines and best thermal seal.
Glass options
Choose the right glass for the job
From everyday thermal gains to specialist acoustic and security performance.
Standard 4mm float glass
An excellent all-round upgrade that delivers strong thermal gains and everyday noise reduction.
Acoustic laminated 6.4mm / 6.8mm
Specialist laminated glass tuned for noise, reducing traffic, rail and aircraft sound by up to 80%.
Low-E thermal glass
A microscopic coating reflects heat back into the room for the best possible energy performance.
Security laminated glass
A tough interlayer resists impact and forced entry, adding a discreet extra layer of protection.
Perfect for
Where secondary glazing makes the biggest difference
Period homes
Victorian, Edwardian and Georgian properties keep their original character and glazing.
Conservation areas
Sympathetic upgrades that satisfy planning rules across London's conservation areas.
Listed buildings
Grade I, Grade II* and Grade II homes gain comfort without altering protected fabric.
Noisy locations
Homes near busy roads, railways or flight paths such as Heathrow, City and London City Airport.
Listed & conservation homes
The conservation-friendly upgrade
Historic England recommends secondary glazing as the preferred way to improve the thermal and acoustic performance of historic windows. Because most installations are fully reversible and sit internally, they usually do not require listed building consent — though we always recommend confirming with your Local Planning Authority first.
We work sympathetically with conservation officers across all 32 London boroughs to deliver upgrades that respect the character of your home.
Transparent pricing
What does secondary glazing cost?
Secondary glazing is priced per window, and the final cost depends on size, system type, glass specification and frame finish. The figures below are typical retail ranges for installed secondary glazing units in London and Hertfordshire — every survey we provide is fixed, written and free of obligation.
| System type | Typical size | Standard 4mm glass | Acoustic / thermal glass |
|---|---|---|---|
| Lift-out / fixed panel | Small (up to 0.8m²) | £350–£550 | £450–£700 |
| Horizontal sliding | Medium (0.8–1.5m²) | £450–£750 | £600–£950 |
| Vertical sliding sash | Medium (0.8–1.5m²) | £550–£900 | £700–£1,200 |
| Side-hung casement | Medium (0.8–1.5m²) | £500–£850 | £650–£1,100 |
| Bespoke bay / angled | Per bay (3–5 panels) | £1,400–£2,800 | £1,900–£3,800 |
Prices include survey, manufacture and installation. Frame colours, hardware finish and glass specification are all included in your fixed written quote — no hidden extras.
Volume discounts available for whole-house installations (5+ windows). Many of our customers spread payments across a 2–3 month installation programme — ask us about phased works during your survey.
How it works
From first call to aftercare
- 01
Survey
Our specialist surveyor measures your windows and assesses the best system for each opening.
- 02
Design
We design discreet units matched to your sightlines, with your choice of glass and finish.
- 03
Manufacture
Every panel is made to measure to the exact dimensions of your original windows.
- 04
Installation
Our fitters install cleanly and carefully, protecting your original windows throughout.
- 05
Aftercare
Your installation is fully guaranteed, with friendly aftercare whenever you need it.
FAQs
Secondary glazing FAQs
Recent projects
Secondary glazing across London & Hertfordshire
A selection of recent installations in period homes, listed buildings and modern apartments.
Hampstead, NW3
Vertical sliding sash glazing, Victorian terrace
Spitalfields, E1
Lift-out panels, Grade II listed Georgian townhouse
Crouch End, N8
Bay window glazing, Edwardian home
Hertford, SG14
Side-hung casement glazing, period cottage
Canary Wharf, E14
Acoustic sliding glazing, riverside apartment
Cheshunt, EN8
Mixed sash & casement, 1930s semi
Explore
Specialist secondary glazing services
Ready to transform your home?
Book a free, no-obligation quote today. Friendly advice, honest pricing and no pushy sales.