Sash windows double glazing

Sash windows double, how double glazing retrofitting can benefit your home and improve your family comfort.

Sash windows double glazing

Can Existing Old Sash Windows Be Double Glazed?

Absolutely, With the right expertise and advanced glazing products, even Graded/Listed properties can be upgraded to double-glazing.

Retrofit into existing sahes

Retrofit into existing windows/sashes:

1. Remove existing single glazing

2. Retrofit new vacuum glazing into existing sashes

3. Change cords and re-balance weights of existing sashes

4. Draft proof the existing sashes

In most cases, original wooden sash windows still have single-pane glazing installed. Our professional team removes existing glazing and, with a few skilful adjustments, install double-pane glazing units.

Where double-glazing units have been fitted already, we can remove and upgrade these. Older double-glazing units fail with age, lose their thermal properties and often detract from the period charm visually.

We use premium-grade double-glazing which is ultra-thin yet high performance. The lead-free, vacuum-sealed units offer exceptional thermal, acoustic and environmental properties. Our installation methods ensure that important original characteristics are retained, living conditions are enhanced and the extended service life is guaranteed.

All windows requiring double-glazing upgrades are carefully measured: we provide custom glazing units of all shapes and sizes – square, oval.

Thermal imaging of our recent double glazing projects

Thermal camera testing of our recent double glazing retrofitting projects.

Thermal heat loss survey of retrofitted windows
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Sash Windows Double glazing
Sash Windows Double glazing
Sash Windows Double glazing

Our projects and customer testimonials

Testimonial — Trevor and Dee

Project: Double glazing existing Georgian Sash Windows with FINEO glass

Double glazing existing Georgian Sash Windows with FINEO glass

Watch Project

Testimonial – Sally

Project: Vacuum double glazing installation

Vacuum double glazing installation

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How long does it take to install double-glazing into existing sashes?

We provide bespoke solutions to each restoration project to ensure best-fit results. For every project, we work efficiently, professionally and with uncompromising attention to detail.

To give you an example of the timescales we operate to:

  •  Our initial assessment allows us to carefully take all measurements and make custom calculations for each replacement glazing unit. This is usually completed within one visit.
  • We can then submit a manufacturing order with the specialist glazing manufacturer. On average, orders are completed within 2 to 6 weeks.
  • Once your custom glazing units are ready, our professional team begins working on all necessary preparations and installations. It is common for glazing installations to be done alongside frame repair and restoration tasks, the installation of drought-proof systems and comprehensive redecorations.

Example project: A typical Victorian property with 10 sash windows, requiring frame restorations, draught-proofing, double-glazing installations and finishing decorations will take 10 to 14 days. Only double-glazing installations will take 5 to 7 days.

It is worthwhile to consider the best time of year for planning double-glazing installations. For your convenience, we usually schedule reglazing work for the warmer months, between March and October. However, we work throughout the year in all months – should you require our professional double glazing retrofitting services to make your home warm, secure and liveable, contact us to arrange an assessment.

Can any wooden sash windows be double glazed?

The most likely answer is yes!

There are a wide range of challenges involved in re-glazing traditional wooden windows which depend on the window’s design and condition. Owing to our expertise, we have never been beaten by a restoration challenge!

Common problems

We encounter and solve when installing double glazing include weak frames which are not designed to take the extra weight. To solve this, we enhance existing frames with hidden metal frameworks and reinforced joints – cleverly installed to safely cope with the additional weight. In sash windows, all necessary counterbalance systems and mechanisms are adjusted and upgraded too.

Other restoration companies can find that the narrow rebates of original wooden windows make it impossible to install double-glazing without altering the authentic appearance. Because we use advanced, ultra-slim double-glazing units, we can comfortably work with original windows, without having to make drastic rebate alterations. At 6.7mm thick, the glazing we use is only 3mm thicker than an average single pane, yet is vacuum-sealed to provide the thermal properties of triple-glazing!

Reinforcing sashes to hold heavier glazing

In older windows, we reinforce wooden frames from within with metal structures. This helps old sashes to hold more weight than the new glass.

Can windows in listed buildings be double glazed?

In most cases, yes!

Because of the progress in technology and manufacturing processes, we can create glazing units that were simply not possible back when your timber windows were originally designed and crafted.

The double-glazing units which we install are ultra-tough yet incredibly thin compared to average double- or triple-glazing. And because they are vacuum-sealed, they offer many advantages and improved performance.

What do revolutionary glazing products mean for your listed property? The thin profile allows us to professionally fit upgraded glazing without compromising on authenticity. The appearance and original design of your windows are not lost – typically, the rebate depth comfortably takes the new panes with only slight modifications needed.

Although the correct permission will be required from your local regulatory authority

listed buildings double glazing

What are the different types of double glazing glass?

We are able to provide a wide variety of glazing options to suit all different needs and window styles.

All are expertly selected and installed to provide maximum benefits and comfort. these are some examples of the double-glazing which we work with to replace your old glazing:

  • Low E-energy Saving Glass

  • Toughened Safety Glass

  • Laminated Safety Glass

Double-glazed window sashes and ensuring smooth operation

When you upgrade to double-glazing, you add multiple benefits including acoustic improvements, excellent thermal efficiency, reduced energy bills and advantages for the environment.

In most cases, additional glazing panes also means the addition of weight. Thankfully, this does not impact on the smooth operation, strength or safety of your windows. With our skilled methods and experience, we make a number of corrections and structural adjustments to leave your sashes running even smoother, stronger and safer than before.

We replace and upgrade sash cords and re-balance your sash windows using additional weights. All pulleys and mechanics are checked and any structural reinforcements are made to ensure that your windows are a joy to use.

Advantages of Double Glazed Windows

When compared with single-glazed windows, double-glazing provides fantastic upgrades and advantages.

From reduced energy bills to quieter and cosier inside spaces, double-glazing can make dramatic changes to your home which can be enjoyed for decades. The superior thermal properties of double-glazing provide a better barrier between internal and external environments and things like condensation build-up is reduced, alongside reductions in subsequent dampness and moulds.

For example, the ultra-slim double-glazing from Fineo reduces perceived noise by over one third when compared with another glazing of similar thickness. And with extra strength comes extra security – especially when toughened security glass is installed.

The market value of your property will also increase when double-glazing upgrades are made using professional restorers. Whether you’re looking to sell your property now or might be planning it for the future, double-glazing can deliver great returns on your investment

Sash windows double glazing

Repairing sash windows prior to double glazing

To properly prepare your existing windows for safely accommodating the additional weight of your glazing upgrade, we provide all the services you need, including sash windows repair.

For a lot of historic windows which still have single-pane glazing, repair of rotten wooden window frames are commonly needed. Over time, original timbers succumb to the elements and need professional restorations to return them to full health. All rotten timbers to frames and any structural damages are thoroughly repaired, ready for the secure installation of new glazing.

Weak frames and original joinery can be reinforced by our team without compromising on appearance. All windows are carefully assessed to ensure the best fit and smooth, safe functioning.

It is common practice for us to install draught-proof systems alongside fitting double-glazing. This further enhances the thermal, acoustic, and functional benefits.

Combining services such as double-glazing, woodwork repairs, decorations and draught-proofing as part of the same project is a great way to really optimise your living conditions, property value and all-around quality. These services all go hand-in-hand and provide an effective, efficient way to complete comprehensive restoration work.

Sash Windows Double glazing
Sash windows double glazing


How does double-glazing work?

The two panes of glass trap air in the small gap between them. This layer of trapped air insulates against heat transfer from the outside to the inside of a property and vice versus. The air trapped between the panes also acts as a barrier for noise and condensation. So, double glazing is basically a clear layer of insulation for your home.

How long does double glazing last?

Most double glazed windows are filled with gas, even modern double glazing. This gas is argon. Over time, this gas will dissipate and disappear. This typically happens in around five years. We use vacuum double glazing technology at Chameleon, though. Vacuum double glazing does the same job as gas-filled double glazing but lasts for much longer. Fineo vacuum double glazing comes with a 15-year guarantee and improved noise reduction and a great deal more. It is why we choose Fineo for all of our window restoration projects. It offers the same heat, noise and condensation protection as triple glazed windows, but in the form factor of double glazing. It is highly energy-efficient and will insulate your home for a lot longer than traditional double glazing.

What’s the difference between secondary glazing and double glazing?

Secondary glazing is an independent layer of glass that is added to the inside of your property, inside the existing window frame. Double glazing is a sealed window unit with two panes of glass separated by an insulating space bar. The gap between the window panes can be filled with gas or vacuum sealed to create an insulation barrier.

Secondary glazing provides better acoustic insulation than gas-filled double glazing, but it is often unsightly and changes the character of a home. However, double glazing is twice as effective at stopping heat escaping from your home and is lower profile than secondary glazing, so it keeps the style the same. A good quality vacuum double glazing, though, beats secondary glazings acoustic insulation properties and double glazings heat insulation. That is why we use Fineo vacuum double glazing in all our window restoration projects.

How can I make my old windows more energy efficient?

If you have an older property with single glazed windows, they can be costing you a lot of money because of how inefficient they are at keeping the heat inside your home. Double glazing is a great option for you. However, many older homes have restrictions about what double glazing units can be installed. For example, listed buildings cannot have double glazing installed that changes the character of the property.  Chameleon installs ultra-thin double glazing into existing old sash window frames that keep the character of a property intact as FINEO double glazing is not much thicker than single glazing, but permission from the conservation officer still required for this type of work. 

Are sash windows energy efficient?

When sash windows were first being used in properties, they were some of the most energy-efficient windows in the world. This, along with the wonderful style, is why so many older properties had sash windows installed. However, over time, the wooden frames can warp and move, which makes them less energy efficient. You can solve this by draught-proofing your sash windows once again. Or you can install ultra-thin double glazing into existing sash window timber frames that are single glazed at the moment. A double glazed sash window is highly energy-efficient and will keep your property looking fantastic. Compared with modern windows, sash windows are not that energy-efficient anymore. But with proper draught-proofing and installing double glazing, sash windows are very comparable to most modern window units.

Why is double glazing better than single glazing at stopping heat?

Double glazing is better than single glazing at stopping heat transfer because of the layers of glass. The gap in between the layers is either filled with gas or vacuum-sealed. This creates a barrier between the air in your home and the air outside. So, if the air in your home is warm and the air outside is cold, the barrier stops the two from mixing and changing temperatures. Put simply, double glazed windows act the same way as the insulation in the walls and ceilings of your home. As a result, double glazing stops the air in your home from reacting to outside temperatures. These windows also help with noise and condensation for the same reasons.

Is secondary glazing cheaper than double glazing?

Yes, secondary glazing is cheaper than double glazing. However, secondary glazing isn’t always the best option. Secondary glazing effectively adds a second window to your existing one. This means that opening the window is fiddly. It also means that you have less of a window sill, which can make space feel much smaller. It can also look unsightly, not so much from the outside but from the inside. While secondary glazing does seem attractive because of the money savings, there are drawbacks to it that you should consider. Double glazing (particularly the vacuum-sealed glazing that we use) doesn’t change the appearance of your home at all and offers much more protection and insulation than secondary glazing and even gas-filled double glazing.

Can you replace single glazing with double glazing?

Yes, you can. The ultra-thin double glazing allows us to double glaze older sash window frames that were initially designed for single glazing only.

Will you need to take my windows away?

No, we complete all work on-site.

What guarantees do you offer?

We offer a 10-year guarantee on paintwork, 20-years on repairs and 15-years on Fineo glass.

How much does it cost to repair, redecorate and double-glazed sash windows?

On average, a sash window restoration (including all repairs and structural improvements), double-glazing installation and complete exterior redecoration cost only £910 per window. Our minimum order quantity is 10 windows.

Will I need to pay a deposit?

We require advanced payment for materials costs, and payment for our services are to be made at the end of the project.