Secondary glazing for periodand listed properties acrossKent, London and Surrey
Keep the original windows, lose the draughts and most of the noise, with a discreet internal glazed system fitted for a fixed written price by the same family-run team since 1998.
Listed-building friendly · £5m Public Liability · 10-year workmanship guarantee
What we do, secondary glazing
Secondary glazing is a slim independent glazed unit fitted to the inside of your existing window. The original window stays exactly as it is, and a second pane, usually in a slim aluminium frame that slides, lifts out or hinges open, is installed within the reveal. The air gap between the two does the work: it cuts noise substantially, stops draughts, and adds a layer of insulation without touching the outside of the building.
This service is for owners of listed buildings and properties in conservation areas where replacing the original windows is not permitted or not wanted, and for anyone on a busy road, under a flight path or near a railway line who mainly needs the noise to stop. We fit it in period houses, flats above shops, converted schools and chapels, and small commercial premises across Kent, London, Surrey and the South East.
Getting it fitted properly is what decides whether you notice it. The frames should follow the reveal and sit behind the original glazing bars so the window still reads as it should from inside and out. Seals must be continuous, because a single gap undoes much of the acoustic benefit, and the opening arrangement has to suit how you actually use the room, including access for cleaning and any escape-window requirement. All of that is a survey question, which is why we measure before quoting.
A snapshot of recent Swift installations
Real photos from projects across Kent, London, Surrey and the South East. Tap through to see the full gallery.
What happens if you leave it
Original single-glazed windows in a period property are usually the loudest and coldest part of the room. On a main road you hear every vehicle; in winter the cold radiating off the glass makes the room feel several degrees cooler than the thermostat suggests, and curtains move on a still night.
For many of these houses the obvious fix is not available. Listed building consent for replacement windows is often refused, conservation areas restrict what can be installed, and leaseholders frequently cannot alter the external appearance of the building at all. Living with it means running heating harder every winter and losing sleep on the street side of the house, year after year.
The mistake we see most often is cheap secondary glazing fitted badly: bulky white frames screwed across the reveal, no continuous seal, and panels too heavy to open, so the room becomes unusable in summer and the windows never get cleaned. Correctly specified secondary glazing should be barely noticeable and easy to operate. That is what we quote for.
From first call to sign-off
- STEP 1
Sales representative visit
One of our sales representatives visits to see the windows and the reveals, discuss what you most need to solve, noise, draughts or heat loss, talk through frame options and opening styles, and outline indicative pricing.
- STEP 2
Surveyor & fixed written quote
Our surveyor attends separately to measure each reveal precisely, check whether the reveal is square, note existing glazing bars, shutters, sills, radiators and any escape-window duty, then issue a fixed written quote.
- STEP 3
Specification
We agree the system, sliding, lift-out, hinged or fixed, the frame colour so it disappears against the existing joinery, the cavity depth for the performance you want, and the glass, standard, acoustic laminate or toughened where regulations require it.
- STEP 4
Manufacture
Units are made to your surveyed reveal dimensions. Lead times are usually shorter than full window replacement, and we confirm your fitting date as soon as the units land.
- STEP 5
In-house fitting team install & sign-off
Our employed fitters fix the frames to the reveal, seal continuously, adjust every opener, and leave the room clean. Nothing on the outside of the building is altered. Your 10-year Swift guarantee covers the workmanship and the units.
What you actually get
Substantial noise reduction
A wide air gap between the original glass and the secondary pane is acoustically more effective than a sealed double-glazed unit, which is why it is used on main roads and flight paths.
Original windows untouched
Nothing is removed and nothing changes outside, which is what makes it viable on listed buildings, in conservation areas and on leasehold flats.
Draughts eliminated
The sealed inner frame stops the air movement that makes period rooms feel cold even when the heating is on.
Warmer rooms, lower heat loss
The trapped air layer reduces heat loss through the window opening, so the room holds temperature better and feels comfortable closer to the glass.
Discreet when done properly
Slim frames matched to the existing joinery colour, set behind the glazing bars, are hard to spot once you stop looking for them.
Less disruption than replacement
Installation is internal, quick and clean, with no scaffolding and no external works, which suits occupied flats and offices.
Secondary Glazing, how we specify
Secondary glazing is simple in principle and detail-driven in practice. These are the choices that decide how well it works and how little you notice it.
Opening styles
Horizontal sliders suit wide casements and bays and are the most common choice. Vertical sliders pair naturally with sash windows and keep the visual logic of the window intact. Hinged casements suit narrow openings and give the fullest access. Lift-out panels are the least obtrusive and best where a window is rarely opened, and fixed panels are used where nothing needs to open at all. We match the style to how the room is actually used.
Acoustic performance and the cavity
Acoustic performance depends mainly on the width of the air gap and the mass of the glass. A wider cavity of around 100mm and above performs noticeably better than a narrow one, and acoustic laminate glass in the secondary pane adds further reduction. Where noise is the main reason for the work, we specify the widest cavity the reveal allows and seal it thoroughly.
Thermal performance
The still air layer between the two panes reduces heat loss and largely removes the cold downdraught you feel beside an old window. Low-emissivity glass in the secondary unit improves it further, which is worth considering on north-facing rooms and on large single-glazed openings.
Listed buildings and conservation areas
Because it is internal and reversible, secondary glazing is generally the most straightforward way to improve a listed or conservation-area window. Consent requirements still vary between authorities and can involve internal alterations to a listed interior, so we check the position rather than assume, and specify slim frames set within the reveal to minimise visual impact.
Condensation, ventilation and escape windows
Trapped moisture between the panes is the classic complaint after a poor installation. Getting it right means sealing the inner frame properly while leaving the original window ventilated to the outside, so moisture does not accumulate against the cold glass. Where a window serves as a means of escape, the secondary unit must open easily and fully. Both are survey questions we resolve before ordering.
Where it is the wrong answer
If your windows are rotten, structurally failing or already modern replacements, secondary glazing is a poor investment and we will say so. In those cases replacement windows or, in a period property, timber and timber-effect replacements are the better route, and we would rather quote you for the right work.
Common questions
How much noise does secondary glazing actually cut?
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A well-sealed system with a wide cavity and acoustic glass typically makes a very noticeable difference on a busy road, generally more than replacing single glazing with a standard sealed double-glazed unit, because the wide air gap is what interrupts sound transfer. The result depends on the noise source, the cavity depth and how well the frame is sealed, so we assess it at survey.
How much does secondary glazing cost?
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Every property is different, so we do not publish rates. Price depends on the number and size of openings, the opening style, cavity depth, glass specification and access. Request a free survey and we will issue a fixed written quote before any work starts.
Will it be visible from inside the room?
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It is visible if you look for it, and largely unnoticeable if you do not. Slim frames finished to match the existing joinery, set within the reveal and behind the glazing bars, are far more discreet than the bulky white systems people remember from the 1980s.
Do I need consent for a listed building?
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Possibly. Secondary glazing is internal and reversible, which is why conservation officers often prefer it to replacement, but requirements differ between authorities and works to a listed interior can still need consent. We check the position for your specific property before anything is ordered.
Can I still open my original windows?
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Yes. Sliding, hinged and lift-out systems all allow you to reach and operate the original window behind, and we choose the style with that access in mind, including for cleaning.
Will it cause condensation?
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Not when installed correctly. The inner frame is sealed and the original window remains ventilated to the outside, so moisture is not trapped against the cold glass. Poorly sealed installations are the usual cause of the problem.
Is it worth it if I already have double glazing?
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Usually not for heat, occasionally for noise on very exposed sites. If you already have modern sealed units we will tell you honestly whether the improvement justifies the cost.
How long does installation take?
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Most homes are completed in a day or two once the units arrive, and the work is entirely internal, so there is no scaffolding and minimal disruption.
What guarantee do I get?
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One 10-year Swift guarantee covering workmanship and the units, with any manufacturer cover included inside those 10 years. Swift Home Improvements Ltd, company number 03679915, installing since 1998.
Can you repair secondary glazing fitted by someone else?
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We only carry out repairs on installations we originally fitted. For existing systems by others, we would quote for replacement.
Do you cover my area?
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London, Kent, Surrey, Essex and the wider South East, from our base at 215 London Road, Stone, Greenhithe. Call 01322 221010 if you are unsure about your postcode.
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FENSA registered·10-year workmanship guarantee· London · Kent · Surrey · South East