Secondary glazing sash windows

New secondary glazing for sash windows offers a solution that removes the need for extra framing on the interior of the primary window.

Upgrading original sashes with vacuum double glazing provides superior thermal insulation and noise reduction while maintaining the aesthetic integrity of the windows by eliminating the need for bulky secondary glazing.

Listed building secondary glazing

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    Why is secondary glazing sash windows considered an outdated solution?

    Many homeowners ask us to remove their secondary glazing and reglaze the original sashes with vacuum glazing, and there is a good reason for this.

    Listed building secondary glazing
    1. Aesthetics – Some people feel secondary glazing looks unattractive from the outside or inside. Extra glazing bars and panes of glass can alter the look of your home.
    1. Reduced natural light – Secondary glazing creates another layer between you and the outside, which can marginally reduce the amount of natural light coming into a room. This may make some spaces feel slightly darker.
    1. Extra cleaning – You now have an extra layer of glass that needs cleaning and maintenance. This adds a minor inconvenience factor.
    1. Cramped Window Operation and Reduced Space: Secondary glazing can make operating the original windows difficult and awkward. The extra framework also takes up valuable space.

    Comparing secondary glazing to reglazing

    Vacuum double glazing provides the same level of thermal insulation as triple glazing.

    In contrast to secondary glazing, the windows are fully refurbished during the reglazing process, eliminating the need for additional budgeting for window restoration.

    Secondary glazing
    Double glazing orignal frames with VIG glass


    Add second framing from the inereor side

    Look sleek as orginal window.

    Listed builsing approval

    Does not need a permission

    90% approval rate

    Thermal insulation

    1.7 W/m²K – 2.7W/(m²K)

    0.48 – 0.7W/(m²K) same as triple glazing

    Noise reduction

    30dB – 45dB Depending on air gap between the existing primary window and the new secondary glazed unit.

    35 dB – 39 dB

    Cost (Materials and installetion)

    £500 – £2200 By installing secondary glazing, you will need to allocate a separate budget for sash window maintenance, whereas reglazing encompasses the cost of sash window refurbishment.

    £1500 per avarage window Price includes window frame restoration, draught-proofing, VIG glass cost of production and installation, painting.

    Cost of refurbishing existing window frames

    no included in secondary glazing price

    Included in the price

    Light transmission


    78% – 79%


    Additional glazing adds additional security.

    Toughened glass

    Listed building secondary glazing

    Transforming original windows with VIG glazing: Key benefits

    Benefits of reglazing your original wooden windows with thin-profile vacuum-insulated glazing units.

    • Retrofitting existing wooden window frames with double glazing preserves their original aesthetic appeal and character while enhancing the windows’ energy efficiency and performance.
    • The use of slim, vacuum-sealed glass units results in superior thermal insulation and soundproofing, rivaling the efficiency of standard triple glazing.
    • Over 90% of our applications are approved.
    • Our process sees over 90% approval rates for applications.
    • We specialize in crafting custom vacuum-insulated glass units tailored to fit the diverse shapes and sizes of historic wooden window frames.
    • Vacuum-insulated glass (VIG) in our double-glazing units boasts a remarkably longer lifespan than traditional double-glazed options.


    An extensive guarantee covers all elements of our reglazing service, providing peace of mind.

    8 Years of paintwork guarantee

    Guarantee on paintwork

    Guarantee on VIG glazing

    Guarantee on repairs made with Accoya

    Cost considerations

    Reglazing traditional sash windows using toughened vacuum insulated glass (VIG) double glazing typically costs around £1700 per window, which includes not only the installation of the VIG but also draught-proofing and comprehensive restoration of the frame and sashes. This price is often on par with or even more affordable than premium secondary glazing solutions for listed buildings.

    Unlike secondary glazing, which simply adds an extra glass pane behind the existing window, this reglazing process incorporates the essential restoration of the window frame itself. This means that you do not have to incur additional expenses for window frame restoration.

    Sash window repair reglazing prices

    What’s included

    Double glazing retrofitting

    Double glazing retrofitting

    Supply and installation of Vacuum Double-Glazing

    Double glazing retrofitting
    Window frame restoration

    Window frame restoration

    Restoration and rot repair for window frames and sashes

    Window frame restoration


    Installation of draught-proofing seals



    Painting of wooden window frames


    Visual proofs of thermal efficiency

    Detailed thermal photographs displaying the reduction in heat loss.

    VIG glazing is more efficient than standard triple glazing.

    Customer testimonials

    Secondary glazing sash windows installation process

    1. Book a free quote —>

      We fully survey your windows and provide recommendations for reglazing and restoration.
    2. We help you with building consent applications. Over 90% of our applications are approved. This is only applicable to Grade 2 listed properties. If your property is not listed, we will skip this step.
    3. When you receive approval, we will place the order for the production of a custom vacuum double-glazed unit.
    4. Our highly skilled craftspeople restore and reglaze your existing sash windows.

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      Past projects


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