Double glazing in London, made in our own factory.
Glazing London supplies and fits double glazing across London, from our Wood Green base to the centre: new double glazed windows, replacement sealed units and upgrades to frames you already have. Our uPVC and aluminium frames are made to measure by our sister company Prime Fabrication, which is why the lead times are shorter and the price is not carrying a showroom markup. Every installation is FENSA certified.
A double glazed unit, from the outside in
A sealed unit is two panes of glass held apart by a spacer bar, with the cavity filled with argon and the whole edge sealed twice. The gap does the insulating, not the glass. Get the gap wrong and the rest of the specification stops mattering.
The pane facing your room usually carries a low emissivity coating, a microscopically thin metal oxide layer that lets short-wave solar heat in and reflects long-wave room heat back at you. It is the single cheapest thing on the unit and it does most of the work.
The cavity
16mm to 20mm argon filled is the sweet spot for a standard London window. Wider is not automatically better. Past about 20mm the gas starts convecting and performance drops back.
Warm edge spacer
A polymer spacer instead of aluminium cuts the cold bridge at the glass edge. This is where condensation shows up first, so it matters more than the brochure suggests.
Low-e coating
Soft coat low-e on the inner pane. Standard on everything we fit, not an upgrade line on the quote.
The seals
Two of them, a primary butyl seal against gas loss and a secondary structural seal. When a unit mists years later, it is almost always the seal that failed, not the glass.
What an A rating means, and when it is worth paying for
Window Energy Ratings run from A++ down to E and combine solar gain, heat loss and air leakage into one letter. Everything we fit as standard is A rated. Going to A+ or A++ costs more and, on a typical London retrofit, pays back slowly.
The exception is a room that is genuinely cold or genuinely loud. If you are fighting traffic noise rather than heat loss, asymmetric glazing, where the two panes are different thicknesses, does far more than another energy grade. Ask us at survey and we will tell you honestly which of the two problems you actually have.
Four ways to hold the same glass
The unit is only half the decision. The frame sets the look, the sightline and most of the price.
| Frame | Best for | Where it goes wrong |
|---|---|---|
| uPVC | Best value per opening, no maintenance, widest colour range through foils | Bulkier sightlines than aluminium, wrong choice on a listed elevation |
| Aluminium | Big openings and slim frames, more glass per hole in the wall | Costs more, and needs a proper thermal break to perform |
| Timber | Conservation areas, period elevations, anywhere planning is watching | Needs repainting on a cycle, which people forget when they buy it |
| Sash | Victorian and Georgian London where a casement would look wrong | Slim double glazing in a sash box is specialist work, not every fitter does it |
Whole window, or glass only
If your frames are sound and only the glass has failed, you do not need new windows. We replace the sealed unit and leave the frame in place, which is a fraction of the cost and a couple of hours per opening. That is the right answer far more often than the industry admits, and it is covered on our misted unit replacement page.
Replace the whole window when the frame is distorted, the hinges and locks are past economic repair, or you are changing the look. A survey tells us which, and we will say so even when the smaller job is the one that pays us less.
FENSA, and why the certificate matters later
Replacement windows are notifiable work under Building Regulations. We are FENSA registered, so every installation is self certified and the paperwork is lodged with your local authority automatically. You get the certificate without applying for anything.
The certificate matters at the point of sale, not on the day. A missing FENSA certificate turns into a solicitor's enquiry and a retrospective building regulation application, which is slow and avoidable.
Is double glazing worth it in a London home?
If the house still has single glazing, or the frames are failing, yes: new A-rated double glazing makes a cold room noticeably warmer and takes the edge off street noise. If you already have double glazing and the frames are sound, new windows are usually money spent too early. A misted unit can be swapped in the frame, and stiff handles, dropped sashes and draughts are a window repair in London, not a replacement.
The third case is the period window you are not allowed to change, or do not want to. There, secondary glazing in London fitted inside the original window often does the job better than replacing it, and it keeps the elevation untouched.
Planning permission, conservation areas and listed buildings
Replacing windows like for like in a house rarely needs planning permission. London is full of exceptions, though. Many conservation areas have Article 4 directions that bring window changes on the front elevation under planning control, flats do not have the same permitted development rights as houses, and a listed building always needs listed building consent.
We check which of these applies at the survey, before you commit to a frame. Where the council will want matching sightlines and materials, our conservation area glazing service covers the timber and slim-profile options that get approved.
Where we fit double glazing in London
We survey and fit across Central and North London. Most of our installations are within a few miles of our N22 workshop: Haringey, Islington, Camden and Hackney, plus Enfield and Barnet on the northern edge. See our North London glaziers page for the boroughs and the housing we see most. Surveys are free and come with a fixed written quote.
Double glazing prices in London
We give a fixed quote after a free survey. These ranges let you sanity-check any price you are given, ours included.
| Job | Typical London price |
|---|---|
| New A-rated uPVC double glazed window, supplied & fitted | £450 to £700 |
| Misted or failed sealed unit replaced, frame kept | £120 to £280 |
Aluminium frames, large or awkward openings and upper floors cost more and are priced at survey. Prices checked September 2026. Full breakdown in our London glazier cost guide.