Double-Glazed Sash Windows
Retain the proportions and detailing of traditional sash windows while bringing greater comfort and performance to your home. Our double-glazed sash windows pair classic design with modern glazing to improve thermal efficiency, reduce outside noise, and provide reassuring security, without losing the appearance that makes sash windows so well-suited to London properties.
Traditional Sash Windows, Built for Modern Homes
Replacing older single-glazed sashes shouldn’t mean losing the proportions and detailing that suit your property.
Our double-glazed sash windows retain the familiar vertical sliding design, with modern glazing incorporated carefully into the window for improved comfort and everyday performance.
Each window is made to order, allowing the specification to respond to the property rather than forcing a standard solution. Choose from timber or PVCu sash windows, with options suited to period homes, sympathetic renovations, and contemporary properties.
With extensive experience working with sash windows across London, we can help you select the right material, glazing, proportions, and detailing for your home, while respecting the architectural style of the building.
Why Choose Double Glazed Sash Windows?
01. Improved Thermal Performance
Modern double glazing reduces heat transfer through the glass, helping your windows provide better thermal performance than older single-glazed sashes.
02. A Quieter Home*
Double glazing can reduce the amount of outside noise entering the property. Where noise is a particular concern, specialist acoustic glazing options can provide greater sound reduction.
03. Greater Everyday Comfort
Improved insulation and weather sealing help address the draughts and cold surfaces commonly associated with older sash windows, making rooms more comfortable throughout the year.
*With our timber sash windows, specifications include a U-value of 1.2 W/m²K, with acoustic laminated glazing capable of achieving up to 39dB sound reduction.
Choose Your Double-Glazed Sash Window
Our double-glazed sash windows are available across five distinct ranges, giving you different options in material, construction, and period detailing. The right choice will depend on your property and how closely the new windows need to follow the original design.
A dependable choice for homes where traditional sash styling and low-maintenance PVCu are the priorities. Run-through horns, glazing bars, and sculpted profiles provide familiar detailing, while modern double glazing, smooth vertical operation, and tilt-in sashes make the windows straightforward to live with.
Developed with period properties in mind, our Traditional range moves closer to the structure of classic timber joinery. Fully mechanical joints, run-through horns, a slim 37mm midrail, and White Woodgrain as standard give the windows proportions and detailing ideal for Georgian, Victorian, and Edwardian homes.
Our most traditionally detailed PVCu sash window. The Heritage range uses a slim 35mm midrail, true mechanical joints, a deep bottom rail, and a choice of period horn profiles to closely replicate traditional joinery. It is particularly suited to heritage-sensitive renovations and properties in conservation areas.
Made to order in timber, these windows allow the proportions, mouldings, and glazing layout to be closely aligned with the property. Traditional cords and weights can be specified where appropriate, with a spiral balance system also available when a slimmer frame and greater glazed area are preferred.
Created for historic properties where original proportions and joinery details need particular attention. Run-through glazing bars, decorative mouldings, and period horn profiles can be carefully recreated, while slimline double glazing and vacuum glazing options allow for modern performance with less impact on traditional sightlines.
30 year guarantee
on timber
10 year guarantee
on paint
Smaller energy bills
and carbon footprint
Timber or PVCu Double-Glazed Sash Windows?
Both timber and PVCu can provide the traditional appearance of a sash window with the benefits of modern double glazing. The right material depends on the property, the architectural requirements, and how closely the replacement windows need to follow the originals.
| PVCu | Timber | |
| Traditional appearance | ✓ | ✓ |
| Double glazing | ✓ | ✓ |
| Heritage options | ✓ | ✓ |
| Tilt-in cleaning | ✓ | — |
| Cord & weight option | — | ✓ |
| Spiral balance option | — | ✓ |
| Slimline / vacuum glazing options | — | ✓ |
Double-Glazed Sash Windows for Period Properties
Double glazing shouldn’t make a traditional sash window look heavy or out of place. The glazing specification needs to work with the proportions of the window, preserving slim sightlines alongside appropriate glazing bars, sash horns, mouldings, and frame details.
For more sensitive period properties, our Heritage timber sash windows can be specified with slimline double glazing or vacuum glazing. These options help retain the slender proportions associated with historic sash windows while still improving performance significantly.
Conservation Areas & Listed Buildings
Georgian, Victorian, and Edwardian homes each have their own window proportions and architectural details. Replacing original sashes with a generic modern window can alter the balance of the facade.
Our Heritage timber range allows original details to be closely replicated, including glazing bars, mouldings, horn profiles, and traditional cord-and-weight operation, with modern glazing options still available.
Our team regularly works with homeowners, architects, and local authorities to help meet conservation and planning requirements.
Thermal Performance & Energy Efficiency
The performance of a sash window depends on the complete specification, not the glass alone.
Our ranges use modern insulated glazing alongside features such as Low-E glass, argon-filled cavities, warm-edge spacer bars, and effective weather sealing where specified.
Performance varies across the range. Classic and Traditional PVCu sash windows achieve a standard U-value of 1.4 W/m²K, while our timber sash windows can achieve 1.2 W/m²K.
Acoustic Glazing for London Homes
For homes affected by traffic or other outside noise, the right glazing specification can make a noticeable difference.
Standard double glazing provides improved sound insulation, while acoustic laminated glass can be specified where greater noise reduction is needed.
Our timber sash windows achieve an acoustic rating of 31dB as standard, with potential performance of up to 39dB when specified with acoustic laminated glazing.
Traditional Details, Made to Suit Your Home
Window furniture can be selected to suit both the sash design and the wider interior.
Select details to suit the age and architecture of your home, with glazing bars, sash horns, mouldings, and frame proportions chosen to reflect the original style where required.
Hardware offers another level of choice. Traditional fasteners, restrictors, lift hooks, and ring pulls are available in a range of finishes, allowing the window furniture to sit naturally alongside existing interior details.
PVCu sash windows can be specified in smooth colours or woodgrain foils, including traditional shades and timber-effect finishes. Our timber sash windows offer further scope to tailor the finish, helping each window feel considered as part of the property.
Box Sash or Spiral Balance?
Our timber sash windows are available with two operating systems.
Traditional box sashes use cords and weights, retaining the familiar mechanism found in historic sash windows and making them perfect for period properties.
A spiral balance uses a concealed spring-loaded mechanism instead. This allows for a slimmer frame, which can increase the glazed area while maintaining smooth vertical operation.
Security Built Into the Window
Our timber box sash and spiral balance windows are tested to PAS 24:2016, with secure sash catches and restrictors available alongside laminated glazing for added protection.
These features are incorporated without detracting from the traditional appearance of the window, allowing period detailing and modern security requirements to work together.
Why Sash Windows London?
We’ve been working with sash windows and London’s period properties since 2005.
With both timber and PVCu sash windows available, we can recommend the right approach for your property rather than steering you towards one material.
Every window is made to order in the UK, with our team managing the project from initial consultation through to survey and installation.
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Our Process
01. Consultation & Quotation
We start with a home visit to understand your property, existing windows, and requirements. We then prepare a detailed quotation based on the recommended products and specifications.
02. Finalising Your Windows
Visit our showroom to see the products in person and confirm the design details. Once approved, we prepare your order and arrange a full site survey.
Find the Right Double Glazed Sash Windows for Your Home
Every property calls for a different approach.
Arrange a home visit to discuss your existing windows, the choice between timber and PVCu, glazing options, and any conservation requirements.
We’ll help you arrive at a specification that works for both your home and the project.
Double Glazed Sash Window FAQs
Can you double-glaze traditional sash windows?
Yes. Our timber sash windows can incorporate modern double glazing within a traditional joinery design. For more sensitive period projects, slimline double glazing and vacuum glazing are also available to help maintain narrower sightlines and traditional proportions.
Are timber or PVCu sash windows better?
Neither material is right for every property.
- PVCu offers lower maintenance and convenient tilt-in cleaning, with several levels of traditional detailing available.
- Timber provides greater scope to recreate original joinery and proportions, making it particularly relevant for historic and heritage-sensitive properties.
Are double-glazed sash windows suitable for period properties?
Yes. Our sash window ranges include options developed specifically with period architecture in mind. Glazing layouts, sash horns, mouldings, frame proportions, and finishes can be selected to suit Georgian, Victorian, and Edwardian properties.
Can I install double-glazed sash windows in a conservation area?
Potentially, but requirements vary between conservation areas and individual properties. We regularly work on conservation-area projects and can help determine an appropriate window and glazing specification for the building.
Can listed buildings have double-glazed sash windows?
Listed-building requirements are property-specific, so double glazing should not be assumed to be acceptable. Our team can work with architects and local authorities when planning a suitable specification.
How energy efficient are double-glazed sash windows?
Performance varies by range and glazing specification. Our timber sash windows can achieve a U-value of 1.2 W/m²K, while Classic and Traditional PVCu sash windows achieve 1.4 W/m²K as standard, with further upgrade options available.
Do double-glazed sash windows reduce noise?
Double glazing can improve sound insulation compared with older single glazing. Where outside noise is a particular concern, acoustic glazing can be specified.
Our timber sash windows achieve 31dB as standard, with potential performance of up to 39dB using acoustic laminated glass.