Can You Double Glaze Existing Windows?

Despite what you may have heard, you can in fact double glaze existing windows. This is done by either secondary glazing or retrofitting, both of which have their own pros and cons. The result of double glazing existing windows is quite different from installing new double glazed windows, as they unfortunately don’t come with the same energy efficiency or noise reduction benefits. Read on for a guide on what double glazing is, how you can double glaze existing windows, and a comparison of new installations vs retrofit or secondary glazing.

What is Double Glazing?

Double glazing refers to a window that has two panes of glass with a gas filled layer between, typically argon. The main benefits most people enjoy from double glazing are keeping heat in during winter and out during summer, as well as noise reduction, these benefits come from their unique design. There are three layers to double-glazed windows; an external pane, a vacuum sealed gas layer and an internal pane, meaning that heat and sound pass through considerably less than other single pane windows. The energy efficiency through insulation is almost 30% better when compared to their counterparts, particularly when combined with a uPVC frame. The soundproofing benefit is even larger when comparing double-glazing windows to single panes, as you can experience a 50% to 80% reduction in perceived noise when making the switch. This is why most people tend to install new double glazed windows for maximum energy efficiency, lower electricity bills and noise reduction.

Ways You Can Double Glaze a Single Glazed Window

As an alternative to installing new double glazed windows, you can install double glazed windows in your existing window frames. There are two types of installation methods for double glazed windows in existing windows – secondary glazing and retrofitting.

Secondary Glazing

Secondary glazing is when an additional window gets fitted over a single glazed window. The extra pane of glass is installed on the inside of the existing window. Adding another layer of glass to the existing window can provide some energy efficiency as it traps the air between the existing window and the new pane. The air acts as an insulator but is not as effective as double glazing with argon gas centre.

Installation involves an initial assessment of the current window frame looking for signs of damage like cracks or rotting. A window frame that is damaged will not be suitable for secondary glazing. The next step is measuring the window you have and cross referencing with the secondary glaze. The secondary glaze is then cut to fit, aligned with the original pane and corresponding window frame, for a perfectly positioned flush finish.

Types of Secondary Glazing

• Permanent Wooden Secondary Glazing: This secondary glazing uses wooden frames to hold the secondary panel in place. It is not the most cost effective solution and the wooden frames can require regular maintenance.
• Magnetic Secondary Glazing: Magnetic seals are used to attach the second pane of glass to the existing window. Unfortunately the panes are usually flimsy and limited in size because of the magnets.
• Secondary Glazing Film: This is a transparent film which is stuck to the window for a double glazed effect. Once in place it is tightened by applying heat. Although it is an affordable solution, it does not look good on windows and eventually becomes visually unappealing.
• Temporary Secondary Glazing: This is a temporary solution for secondary glazing and can be a simple lightweight screen added to the single glazed window. It can be attached and removed whenever necessary but can make it difficult to wash and clean windows as it always has to be removed.

Retrofitting

Retrofitting is when double glazed windows are installed in existing window frames. The double glazed windows are constructed, the original single glazed pane of glass removed, and the double glazing is installed in the original frame. Unlike new double glazed window installation, which includes the installation of a new frame and double glazing, retrofitting preserves the existing frame. It is a more energy efficient solution than secondary glazing as the double glazed window will include the vacuum sealed layer filled with argon gas. However, the state of the current window frames and the type of material used will impact the energy efficiency of the retrofitted double glazed window.

Why Double Glaze Existing Windows?

For some people, double glazing existing windows may be viewed as a way to improve energy efficiency without having to invest in brand new double glazed windows. Double glazing existing windows can definitely help improve energy efficiency and reduce bills, but not to the extent that new double glazed windows can provide. The reasons for double glazing existing windows include:

• No structural changes: there is no need to remove or replace frames.
• Slight reduction in energy bills: a second pane of glass will reduce energy bills slightly.
• Slight noise reduction: noise may be reduced but not as significantly as double glazing.
• Cost effective alternative: it can be a cheaper alternative than double glazing.

Will I be Able to Double Glaze my Current Windows?

Whether or not you can double glaze your current windows will depend on the condition of the windows and frames. If you want to have double glazing retrofitted into a current window, the frame will need to be strong enough to support the extra weight of the double glazed window. If it is degraded or cracked, existing measures will need to be taken to repair or replace the existing frame which could become costly. For maximum energy efficiency from the secondary or retrofitted double glazing, the frames need to be in good condition.

In terms of installing your own double glazing in existing windows, there are some kits available for secondary glazing. However it is important to remember that any do it yourself project may not be as well sealed and effective as a professional installation. Retrofitting double glazed windows must be carried out by a professional.

Pros and Cons of Double Glazing Existing Windows

While double glazing existing windows can seem like a cost effective way to improve energy efficiency and reduce noise, there are some major drawbacks.

Pros of Double Glazing Existing Windows

• Cost effective: secondary glazing costs about $500 to $600 per square metre, which is less expensive than new double glazing.
• Energy efficiency: double glazing existing windows does improve energy efficiency in the home to an extent. However, the level of efficiency will depend on the type of double glazing used, and the quality of the existing frames.
• Noise reduction: some double glazing installed in existing windows can reduce noise by about 30% but new double glazing with high quality uPVC frames may reduce outside noise by up to 80%.
• Installation ease: simple secondary glazing can be an easier installation process.

Cons of Double Glazing Existing Windows

• Not as efficient as new double glazed windows: double glazing existing windows will be more energy efficient than single glazed windows. However, they are about half as effective as new double glazed windows in terms of energy efficiency.
• Potential for condensation: secondary glazing and retrofitting will not reduce the level of condensation. As the glazing is fitted in the existing frame, it will be less well sealed compared to double glazed windows. This may cause condensation to form between the glass panes.
• Limited sill area: when an extra window pane is installed in the original frame it will decrease the amount of window sill area.
• Maintenance issues: original window frames may become warped or loose over time and this compromised frame impacts secondary or retrofitted double glazing performance.
• Aesthetic issues: sometimes an extra layer of glass can look out of place particularly when installed in an old window frame. Double glazing in existing windows can change the appearance of the windows and look unattractive especially if not fitted correctly. New double glazed windows are available in a variety of sizes and styles to suit any type of home.
• Hard to clean: secondary glazing has four glass surfaces to clean and because of the nature of how they are installed, it can be difficult to get to each glass face to clean. Double glazed windows are extremely low maintenance, as they are professionally installed to ensure maximum sealing, it is guaranteed nothing can build up inside the window. The only thing to clean is the interior and exterior panes of glass.

When researching double glazing it is understandable to consider double glazing existing windows over new double glazed windows. On paper, new double glazed windows, secondary glazing and retrofitting have similar effects. They can all add energy efficiency, help reduce bills and cut down noise pollution. However, there are some major differences to be aware of when making your decision. New double glazed windows are far more energy efficient which will ensure more savings in energy costs. Secondary glazing and retrofitting may be good short term solutions but can still end up costing more money in maintenance and potential replacement. If you are interested in finding out more on whether to double glaze your existing windows or install new double glazed windows, contact the team at Windows For Life.