Sash windows double glazing

Retrofitting double glazing to wooden windows can improve energy efficiency, increase comfort and reduce energy bills.

Sash windows double glazing

Can Existing single glazed sash windows be double glazed?

Absolutely, with the right expertise and slim-profile double glazing, even original sash windows in historic properties can now be double glazed.

sash windows repair in braintree

Retrofitting Double Glazing To Wooden Windows

1. Remove existing single glazing

2. Retrofit new slim-profile vacuum glazing into existing sashes

3. Change cords and add additional weights to counterbalance the additional weight of the new heavier glass. Service pulleys and add new cords.

4. Draft proof the existing sashes

In most period properties, original sash windows still have single-pane glazing installed. Single glazed windows are not energy efficient, as the consequence, homeowners pay higher energy bills and have condensation on their window panes during colder winter months. Single glazing also has low acoustic insulation properties.

Retrofitting double glazing to wooden windows is done by removing existing single panes of glass and installing new slim-profile heritage double glazing.

We use slim profile, vacuum-sealed units with exceptional thermal insulation properties, equivalent to triple glazing. Our installation methods ensure that important original characteristics of the historic property are preserved, living conditions are enhanced and the extended service life is guaranteed.

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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Advantages of sash windows double glazing

Thermal efficiency

When compared to the thermal performance of single glass pane windows, double-glazed units reduce heat loss and improve the energy efficiency of original sash windows by up to x8.

Vacuum, slim-profile double glazing (only 6.7-10mm) with Low-E glass has the same thermal and insulation properties as 36 mm triple glazing. It also beats by energy performance the standard heritage double glazing with laminated glass and insulated with inner gasses such as Krypton and Argon.

improve thermal efficiency

Single glazing vs vacuum and slim double glazing and triple glazing

To the box with different glazing options, we inflated hot air and used the thermal camera to capture the heat loss of each glass.

External noise reduction

By retrofitting double glazing to wooden windows the noise pollution from outside of your house will be reduced in half.

For example, the Fineo glass has acoustic performance that reduces perceived noise by over one third when compared with single glazing. If you live on a busy road, this reduction in external noise will help you sleep longer in the morning instead of waking up with the first commuters.

Better sound insulation


Double glazed units are harder to break, so they increase the house’s safety.

Where required by building regulations, the units can be made using toughened glass (laminated glass or tempered), which is even more secured.

increased security

Increase the value of your house

The market value of your property will also increase after retrofitting. 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 as windows are one of the most important parts of the house, one the poof comes before windows.

Our projects and customer testimonials

Testimonial — Trevor and Dee

Project: Double glazing Georgian sash windows with FINEO glass

Double glazing Georgian sash windows with FINEO glass

Watch Project

Testimonial – Sally

Project: Vacuum double glazing installation

Vacuum double glazing installation

Watch Project

How long does it take to retrofit double-glazing to wooden windows?

  •  After the quote is accepted, we take glass measurements and place the order with the glass manufacturer.
  • Manufacturing and delivery take on average 6 weeks. The glass is either delivered to your address or our premises.
  • Once the glass is delivered, we do a quick inspection and schedule the work.
  • On the agreed day and time, our team comes and does all retrofitting, restoration and painting work.

On the 15 sash windows project, our team will usually spend around 12 working days. The work will include wooden frames refurbishment, retrofitting and painting.

Can you retrofit double glazing to any wooden window?

The most likely answer is yes!

There is a wide range of challenges involved in retrofitting double glazing to wooden windows. It all depends on the condition of the wooden frames, access to the window and the size required.

Specials shapes double glazing

Specials shape

Slim-profile double glazing units are now can be manufactured in special shapes: curvedfull-curvedtrapezoidal or oval shapes.

Specials shape double glazing units

Minimum and Maximum dimensions

Maximum: 1.50 m x 2.50 m or 1.60 m x 2.40 m
Minimum: 0.20 m x 0.20 m

Common sash window double glazing challenges

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!

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.

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 that we work with to replace your old glazing:

  • Low E-energy Saving Glass
  • Toughened Safety Glass
  • Laminated Safety Glass

Functional restoration

Additional glass panes also mean the addition of weight. Thankfully, this does not impact the smooth operation, strength or safety of your windows. Correct adjustments of weight and pulley system will 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 serviced. We also straighten sash joints while doing other restoration work on wooden frames and sashes.

Sash windows double glazing

Repairing sash windows prior to retrofitting

To properly prepare wooden 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.

Retrofitting Double Glazing To Wooden Windows


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. 

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.

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.