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Sash window double glazing

Sash Window Double Glazing Guide

Contact us Sash Window Double Glazing Guide

Upgrade single glased sash window with double glazing units

Restoration, draught-proof, Double Glazing

Windows play an important role in the energy balance of a house. In old buildings, windows are often replaced with new ones or, for economic reasons, by PVC windows, but the aesthetic appeal is greatly impaired. This is why we have developed a double glazing solution for sash windows, which can finally combine aesthetics and “triple glazing” energy performance.

Our sash window double glazing method preserves your wooden windows and doors, restores them and improves thermal properties. The result is an original window frame is fully refurbished and the thermal properties of the glass are improved up to 8 times compared to single glazing.

Our technique allows us to treat both classic sash, casement windows and all special shapes (curved, trapezoidal, elliptical, etc.) in opening or fixed while preserving the charm and the original frames of the window.

The Georgian bars remain unchanged on the inside and are identical on the outside. We can add or remove them to alter the style of the sash window if you would like to change the Victorian style sash window to Georgian for example.

Example of originally single glazed sash window which now retrofitted with 7 mm slimline vacuum double glazing.

Double glazing existing sash windows

Double glazing old Georgian style sash windows

Double glazing old Georgian style sash windows

When we install double glazing into the original Georgian sash window, our team keep beautiful Georgian bars from inside untouched. Georgian bars and putty on the exterior side of the sashes will be identical to the original after double glazing is retrofitted into the frame.

Victorian sash windows

Adding double glazing to existing Victorian sash windows

Less glazing bars window has, more straight forwards is reglazing process.

It is less expensive to install double glazing into existing Victorian sash windows with no glazing bars on sashes.

double glazing any existing wooden windows

Double glazing any wooden windows

Double glazing units are now available in all special shapes and size; oval, arch and even bowl.

fineo special shapes

Any sash window style can now be double glazing.

A professional sash window double glazing service ensures exceptional results:

  • The frame and aesthetics of the sash window are perfectly preserved.
  • We improve both thermal and acoustic performance of old sash windows.
  • Complete finish as paiting is included in our double glazing service.
  • We work on site in our mobile workshop.
  • Any sash that we take for double glazing in the morning is installed back to the frame in the evening.

Double glazing benefits

If you’re considering installing double glazing into your period home, you likely have a few issues with your windows that need sorting out already. After all, if your windows were working great, you wouldn’t be here. Well, double glazing has many benefits for listed properties, including

sash window heat lost

10-31% of heat is lost through windows

Double glazing can create a barrier and stop heat from escaping from your home. We can also draughtproof your sash windows to ensure that they are working just right for your home.

stop uv radiation window glazing

Stop UV Radiation

UV light is dangerous to us and our homes. Single glazed windows let a lot of UV light into a home, which can discolour paint, furnishings, artwork and wooden features in your home. Double glazing can greatly reduce the amount of UV light coming into your home.

reduce-noise pollution for better sleep

Reduce noise pollution for better sleep

Double glazing can greatly reduce the noise that enters your home. Single glazed windows bring a lot of noise pollution into a property, and you’ll be amazed at how well our double glazing can reduce this noise.

double glazing to existing frames

Fitting double glazing units to existing wooden frames

For both new double glazed sash windows and refurbishment projects, vacuum double glazing can be adapted to different window styles without significantly altering their look.

Slimline vacuum double glazing units can also replace an existing single pane of glass in old wooden frames to improve the sound-proofing properties and thermal performance of the building, reducing energy bills.

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Wooden window double glazing process in 3 steps


Removal of sashes

No major work inside the home as a result you will experience minimum distraction to your day to day life.

Our team will take down sashes to our on side workshop and will reassemble them back to the frame at the end of each day.  


Rebating frame

Rebating sashes

Rebating the exterior side of the sashes to accommodate the double glazing. 

At this stage, we also remove old paintwork from the sash window frame and sashes.  Repair and make stronger window frame joints, remove rot and replace it with solid new timber. 


Fitting glazing units

Fitting double glazing units

Fitting draught-proofing seals into grooves previously made around the window frame, then fitting of the double glazing units and fixing them with new putty from the exterior side.

Once a sash is double glazed, it is installed back to the frame. We add additional weight to offset the heavier glass and the whole window is painted.  

Double glazing for listed buildings

Listed buildings can significantly benefit from double glazing. Many listed buildings have draughty and damaged wooden window frames and are mostly single glazed.

If you live in a listed building and are looking into replacement windows options, we believe that double glazing retrofitting is a more sympathetic solution for old sash windows.

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In addition to saving money on new double glazed windows replacement, by retrofitting your windows with double glazing you are contributing to the collective effort to reduce greenhouse gases.

Slimline double glazing

There are a number of slimline double glazing products available on the market which are suitable for double glazing existing sash windows or double glazing windows in listed buildings. 

Vacuum double glazing

Stop UV Radiation window glazing

Heritage slimline double glazing

Double glazing for listed buildings

FAQs about sash window double glazing

How much does it cost to install double glazing into single glazed sash window?

Sash window double glazing retrofitting prices start from £1200 pounds per sash window but it does not include timber frame restoration, as well as no painting. We usually charge £1800 per window for all-inclusive window restoration and double glazing service. 

Can you install draught-proofing seals into old wooden windows?

Yes, we can draught-proof windows as a part of our sash window double glazing service package. 

Which area does your service cover?

We mainly work in East Anglia but we also have projects in South East, it all depends on a number of windows.

Can you install double glazing into existing window frames ?

Yes, the double glazing that we use in our projects is only 7 mm thick,  it can be fitted into old narrow, wooden sashes.