For listed and period homes
Secondary Glazing
For windows that have to stay. A slim frame goes on the inside of the one you already have, so nothing is cut, nothing is removed and the front of the house does not change. It is what goes into a listed home, a conservation area, or anywhere the original window is the thing worth keeping.
What it is
The original window stays. This goes in front of it.
A slim frame is fitted into the reveal in front of your existing window. The original is not touched: same glass, same frame, same view of the house from the street. What changes is that there are now two windows with a run of air between them, and that gap is the part doing the work.
Nothing is cut and nothing is removed, so it can come back out and leave the window as it was. That is usually the point in a listed home: what is there stays there, and the one change made to the room is a change you could undo.
- Nothing comes out, and the outside of the house does not change
- Slim aluminium frames in white, brown or any RAL colour
- Priced on our online designer, the same as the windows
Why people have it
There is really only one reason.
Almost nobody comes to secondary glazing first. They come to it because replacing the window turned out not to be an option. The quiet and the warmth are what they find afterwards, and are not what got them on the phone.
- The windows have to stay
- A listed building, a conservation area, or a flat where the windows are not yours to change. Original leaded lights or stained glass worth keeping is the other one. Secondary glazing goes on the inside and takes nothing out, so what is there stays there.
- Then the road gets quieter
- Two separate windows with a run of air between them is a different thing from one sealed unit, and the air gap is what slows sound down. If noise is the part you most want dealt with, say so early, because it changes the glass we would put in.
- Then the room gets warmer
- Single glazing loses heat and old frames let draughts through around the edges. A second glazed layer on the inside slows both of those down, in a room where the usual fix was never available.
How it opens
You can still open the window behind it.
This is the question we get asked first, and the answer is yes on everything except the fixed and lift-out panels. You open the secondary glazing, reach the original catch, open the window itself, and close both again. The photograph is one of ours with the original casement wide open behind the glazing.
Which of the five suits an opening depends on the window behind it and on what is in front of it in the room. We work that out at survey rather than asking you to.
The five styles
Five ways it opens, and how slim the frames are.
Two numbers matter on any of them: how far the frame stands into the room, and how much of it you see before the glass starts. They are drawn to one scale, so you can compare them.
Horizontal slider
Panes run sideways past each other on a track. Nothing swings into the room and nothing needs clear space in front of it, which is why it suits a window behind a deep sill or a radiator.
- Front to back
- 39mm face fix, 56mm reveal fix
- Outer frame edge to glass
- 47mm
- Fixing
- Face or reveal
Vertical slider
Panes move up and down instead of across. It is the one for a sash window, and for a tall narrow opening where a sideways track would have nowhere to go.
- Front to back
- 39mm face fix, 55mm reveal fix
- Outer frame edge to glass
- 56mm
- Fixing
- Face or reveal
Hinged
Opens towards you like a casement, so the whole original window is in front of you at once. The choice where you need proper access rather than a gap to reach through.
- Front to back
- 39mm face fix, 55mm reveal fix
- Outer frame edge to glass
- 70mm
- Fixing
- Face or reveal
Fixed
A single pane sealed into its frame, which is where it stays. The one for an opening nobody uses, where nothing behind it needs reaching and there is no reason for it to move.
- Front to back
- 12mm
- Outer frame edge to glass
- 20mm
- Fixing
- Face fix only
Lift-out
Does not open either, but it is made to come out. The pane lifts away in your hands and goes back afterwards, so the original window is still reachable when you want it without the glazing being a fixture.
- Front to back
- 30mm face fix, 49mm reveal fix
- Outer frame edge to glass
- 40mm
- Fixing
- Face or reveal
The sections and the sizes are the manufacturer's. Which style suits an opening, and whether it fixes to the face or into the reveal, is settled at the survey.
Glass and finish
If noise is what you want dealt with, the glass is the decision.
Standard glass is enough where the job is warmth and draughts. Laminated glass is the upgrade, two sheets bonded around an interlayer, and it is the one to take if traffic or a flight path is the thing you most want quietened. It is worth saying so on the phone, because it is specified at the start rather than added later.
The frames are slim aluminium and sit inside the reveal, which is what stops a second window looking like one. White and brown are the two standard colours, and any RAL can be matched where a frame needs to disappear into a dark reveal or pick up something already in the room.
- Laminated glass upgrade where noise is the priority
- White, brown, or any RAL colour
- Frames sized to the reveal, so they sit back rather than stand out
Product questions
FAQs about Secondary Glazing
Will it stop me opening my window?
No, unless you choose one of the two styles that do not open. Horizontal sliders, vertical sliders and hinged units all open, so you reach through, work the original catch and open the window behind exactly as you did before. A fixed panel is sealed into its frame and stays there, for an opening nobody uses. A lift-out does not open either, but the pane comes away in your hands and goes back afterwards, so the window behind it is still reachable.
Can I have it on a listed building?
It is the reason most people have it. Nothing is removed and nothing is cut, the original window stays exactly as it is, and the outside of the building does not change. Your local authority sets the rules for your property, so check with them before you order, and we will work to whatever they tell you.
How does it compare with replacing the windows?
They do different jobs. A new window brings the frame, the seals and the glass up to standard in one go, and it is the answer where the existing window is past saving or has to come out anyway. Secondary glazing leaves the original where it is, and the run of air between the two windows is far deeper than the cavity inside a sealed unit, which is the part that works on sound. Ask for the laminated glass upgrade if noise is the part you most want dealt with.
Will it look obvious?
The frames are slim aluminium and are made to sit back inside the reveal rather than stand proud of it, so from inside the room the eye reads the original window first. White and brown are the standard colours and any RAL can be matched if a frame needs to disappear into a darker reveal.
Can I get a price online?
Yes. Secondary glazing is on our online designer alongside the windows and doors, so you can size it, choose the style and get a real figure without waiting for anybody to call you back.
Order process
A clear process from first quote to aftercare.
Four steps. The first one has two ways in: price it yourself online, or have us come out. After that it runs the same either way.
Your price
Price it yourself on the online tool, or book a free consultation and we build the same quote with you. Both run on the same price list, so the figure matches.
Technical survey
Once you go ahead we survey before anything is made. Not a second sales visit: the reveal depth, the fixings and the sizes the factory needs to build it right.
Installation
Fitted by our own installers rather than subcontractors, trained on the systems we sell and working carefully in a house someone lives in. We clear up after ourselves before we leave.
Aftercare
Anything afterwards, you ring us rather than a call centre, and you are talking to the same people who fitted it. We look after our own work rather than passing you on.
What Milton Keynes homeowners say
Real reviews from real installations. Every one is public, so you can go and check them yourself.
Stuart Matthew
7 months ago
Fenster have just completed a front door installation on my new property - fantastic job and strongly recommend! The online design tool is great, Perry back at HQ is brilliant as is his communication. Andy, who installed the door, is a top gent and professional. Will definitely be a returning customer.
Read on Google
Joanna Hayes
3 months ago
Really happy with the service we received from Fensters Windows. Aaron and Shane turned up on time and were both really friendly. They explained any issues as they went along and talked us through the different options, which we really appreciated. They did a great job fitting our new back doors and cleaned up everything afterwards. We also paid exactly what we had originally been quoted, with no unexpected extra costs. Really pleased with our new doors and would definitely recommend Fensters Windows. Thank you Aaron and Shane!
Read on Google
Digger
3 months ago
We have used Fensters for years on a variety of glazing work, and 2 door installations. They are competitively priced and responsive. They take great care over measuring and specifying the work, giving you a clear quote so you understand what you are getting (thanks Perry!). The fitters are all extremely competent and personable. We had to replace our front door for accessibility reasons, they gave us confidence that our requirements would be met, reproduced the intricate leaded and stained-glass pattern of our old door, and did a quality fitting job (thanks to Johnnie and Shane!). In summary they are our go-to suppliers for all replacement and repair work.
Read on Google
Silvia Peraro
2 months ago
I had an excellent experience with Fenster Glazing from start to finish. Nick Perry and David managed the initial quote to installation process seamlessly, keeping communication clear, honest, and completely stress-free. When it came to the actual fitting, Zac and Shane did a fantastic job with the installation, working efficiently and leaving everything spotless. The professionalism from the entire team was top-notch, and the final result looks brilliant. I highly recommend them.
Read on Google
Bernie Raffe
4 months ago
Great service from Fenster Glazing, very happy with our new bi-fold door, glass door and windows (with built-in blinds) There was an issue with the wrong spec of glass provided to them from their supplier, so they had to temporarily board up a door and a window, but this was put right within a few weeks. Recommended, thanks.
Read on Google Zak Jessup 12 Jun 2025Cannot recommend higher! Nick and Perry were really helpful in getting my windows sorted ASAP.
Read on Google Norman Cummings 10 Jun 2025The best service ever, great workmen, very high standard and in the finish, excellent eye to detail.
Read on GoogleFrom our case studies
Real installs, photographed on the day.
Start your project
Tell us about your project.
Send the basics and the team can guide you through styles, pricing, survey and installation options.
Keep exploring
