Frequently Asked Questions

Retrofit Double Glazing: The Top 30 Questions Answered

When choosing the best retrofit double glazing option for your home there’s a lot to consider. So, here’s a list of the things we get asked most.

Here’s everything you could ever need to know about our retrofit double glazing system, ecoGlaze®.


There’s a lot to learn about retrofit double glazing. Click on the questions below to reveal the corresponding answer.

What other double glazing options are available?

In this interview, thermal comfort expert, Maurice Beinat compares the different double glazing options available. Gain insight into the effectiveness of:

  • heat shrink film
  • insulated glazing units (replacing the glass, keeping the frame)
  • traditional replacement double glazing
  • glass that is thick vs. glass that is thinner
  • double glazing and single glazing in direct sun strike
  • secondary glazing (retrofit double glazing)
How much ecoGlaze cost?

A reasonable indication is around $450 per square metre installed, depending upon the type and size of your windows and your location. However, some types of glazing, such as double hung windows, can cost more.

How does it work?

ecoGlaze® Retrofit Double Glazing works by trapping a layer of still-air between your existing windows and the ecoGlaze® acrylic panel. This layer of air greatly reduces the heat transfer through your glass window. The acrylic panel is secured in place by beautifully made timber mouldings held firmly to the window frame with invisible magnets.

Is ecoGlaze® available for both timber and aluminium frames?

Generally speaking, the ecoGlaze® Retrofit Double Glazing System can be easily applied to all timber windows and some aluminium windows. This is dependent on the window frame having enough room for the ecoGlaze® system and sufficient insulating air pocket. Some residential aluminium-framed windows do not allow enough space for the ecoGlaze® system to fit. However, many homes (particularly apartments) are fitted with commercial aluminium window frames, which are often the perfect size.

Is ecoGlaze® suitable for glazing in doors too?

ecoGlaze® is a suitable treatment for timber framed glazing, doors included. It can be applied to French doors; sliding doors; hinged doors; doors with colonial bars; or doors with lead lighting.

Will I have to remove ecoGlaze® to open my windows and doors?

No, the ecoGlaze® Retrofit Double Glazing System does not alter the operation of your windows or doors. You will be able to open them normally.

What size windows is ecoGlaze® appropriate for?

The largest ecoGlaze® panel that can be safely installed is 3000mm x 2000mm.

Will it make my windows look ugly?

ecoGlaze® is a truly elegant product designed to satisfy even the most discerning home owners. Its sleek timber frame blends with your existing joinery to provide a seamless solution. The optical grade acrylic panel is crystal clear, to preserve your view.

This is one of the most important features of ecoGlaze®.

The ecoGlaze® Retrofit Double Glazing System is supplied in either raw timber (Tasmanian Oak) or White powder coated aluminium. The raw timber mouldings are ready to be stained and finished to match your existing window frames.

Will ecoGlaze® eliminate noise?

ecoGlaze® is primarily a thermal product, that means it is designed to improve the comfort of your home in summer and winter.  All forms of secondary glazing will reduce street noise to some extent, however, while it provides some acoustic benefit, its major focus is to vastly improve the thermal performance of the glazing in a way that is aesthetically beautiful.

Neither ecoGlaze® nor any other form of retrofit double glazing will totally eliminate external noise from your home and should not be viewed as a complete sound-proofing solution. Sound travels around building elements and so it can travel around an acoustically effective window or door.

Any noise abatement should be undertaken in a holistic manner and would usually include thorough draught proofing as well as treatments to the walls, floors and ceilings. Often in apartments the glazing is the major source of noise infiltration and, therefore ecoGlaze® would provide significant acoustic benefit.

How do I get someone to come and quote?

Yes, you can. Click on this link and an experienced ecoGlaze installer will be in contact with you.

My home is freezing cold in winter, will ecoGlaze® help with that?

Yes it certainly will. ecoGlaze® will reduce the heat loss by more than 50%, making a huge difference to the comfort of your home.  This will significantly save you on your winter heating bill because you will need to use your heater much less. 

It is important to recognise that there are other higher impact retrofit activities that you should undertake first, in order to maximise your retrofit dollar. Draught Proofing, Ceiling Insulation, and Underfloor Insulation should all be undertaken prior to any changes with your home’s glazing.

I have problems with heat in summer, will ecoGlaze® help with that?

Even traditional double glazing solutions cannot solve the problem of direct summer sun striking the glass.
Providing there is no direct sunlight striking your windows,the ecoGlaze® Retrofit Double Glazing System is highly effective in making sure that the summer heat stays outside. ecoGlaze® will reduce the heat transfer by up to 50%. However, if there is direct summer sun striking the glass, then external shading is the appropriate solution.

How does ecoGlaze® compare to brand new double glazed windows?

Brand new double glazed windows are much more expensive than secondary glazing. There is also a considerable amount of effort involved in selecting, arranging, installing, plaster repair, painting and cleaning up afterwards.

With replacement windows, the old heavy windows also need to be removed and properly disposed of. Tradesmen need to install the new windows carefully and the architraves and plaster around each window replaced or repaired. Finally the painters will need to repaint walls and / or architraves to match your existing paintwork.  It can be challenging to co-ordinate multiple tradespeople in a timely manner when trying to get your home back to normal.

Also, we often we hear that people are disappointed to find that their brand new double glazing does not allow the adequate still air space to deliver the comfort they paid for.

Installing ecoGlaze® in your home is a relatively simple and clean process that takes approximately one hour per window.  No other structural changes are required. 

How does the ecoGlaze® Retrofit Double Glazing System compare to replacing the glass with a double glazed unit or insulated glazing unit (IGU)?

There are a number of glazing companies that provide this service.  Please be mindful that your original window frames were designed for a single pane of glass and are weighted to allow them to open and close normally.  So there are two issues with replacing the glass:

  • Adding an IGU to single glazed windows will make them very heavy. The additional weight is often too heavy to allow the windows to self-support in an open position. Doors that have been treated this way often experience strain on the hinges or tracks which can cause problems in the future.


  • The smaller the gap between layers of glass, the less effective it will be. Because your original frames were designed for a single pane of glass, they were not constructed to accept wider glazing units.  This forces the replacement glazing (IGU) to be very narrow, fitting two layers of glass into a space that was designed for one layer.  This compromises it’s thermal effectiveness as the gap will allow conduction of heat and cold, which is exactly what you are trying to avoid.

ecoGlaze® has none of these problems because it weighs much less than glass, allows your windows to open and close normally. Its design provides the best possible still-air space to maximise thermal performance.

Is the ecoGlaze® unit sealed?

It is not necessary for the ecoGlaze® system to be sealed. ecoGlaze® creates a still-air space between the existing glass and the added acrylic panel. It is the still-air space that provides the insulative effect in ecoGlaze® and all other forms of secondary or double glazing.

Is the ecoGlaze® unit filled with argon gas?

ecoGlaze® does not contain Argon or any other chemical element.  Argon filled double glazing is one of the most expensive types of double glazing available. It is important to note that Argon provides virtually no additional benefit unless it is combined with a ‘low e coating’, which requires the glass to be replaced.

Why use acrylic instead of glass?

There are a number of reasons why the ecoGlaze® Retrofit Double Glazing System has been designed using an acrylic panel instead of glass:

  1. Due to its flexibility acrylic is very difficult to break which makes it extremely safe.  By comparison, glass is brittle, rigid and will shatter on impact.
  2. Acrylic is far less conductive than glass, which means that it will retain your winter warmth and protect you from summer heat transfer. In fact, acrylic conducts five times less than glass.
  3. Acrylic is light weight and easy to handle it can be safely added to your existing windows. As glass is a rigid, dangerous product, there are stringent safety requirements. It is not economically viable to be compliant with the Australian Glazing Standard if glass is used for this purpose.
WERS Rating (Window Energy Rating Scheme)

The level of conduction of heat is measured by a number called a U-value. The U-value is measured by 1/R where R is the rate of heat resistance. The lower the U-Value, the better the performance of the glazing.

The U-value of a 3mm single glazed window with aluminium frame is 6.9. Compare this to a double glazed unit, with 6mm spacing and aluminium frames, with a U-value of 3.8.  ecoGlaze® will be able to take a wooden framed single glazed window with a U-value of 5.5 down to a secondary glazed unit with a U-value of 3.0.

What does Solar Heat Gain Co-efficient (SHGC) mean?

SHGC measures how well a product blocks heat caused by sunlight. The SHGC is the fraction of incident solar radiation admitted through a window, both directly transmitted, and absorbed and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window’s SHGC, the less solar heat it transmits.  ecoGlaze carries a SHGC between 0.57 to 0.61.

Does ecoGlaze® come with a warranty?

ecoGlaze® uses the highest quality extruded acrylic panels for the glazing materials. This material is manufactured in Germany to a high degree of precision so that, optically, it is virtually indistinguishable from glass. It has a 7-year warranty against discolouration and crazing.

Will condensation effect ecoGlaze®?

Secondary glazing (retrofit double glazing) works the same way as factory made double glazing by providing a layer of still air that improves the insulation value of otherwise highly conductive glass. In factory made units you have the opportunity to select many glass treatment options and also a gas fill. These units are hermetically sealed and have desiccant in them to absorb any water vapour that may impregnate the seals.

The ecoGlaze® Retrofit Double Glazing System is not sealed and does not include a desiccant. It relies on the water vapour in the air not being so high as to create condensation in the air space. This means that of all of the Melbourne-based installations we have carried out, there have been no reports of a moisture problem.

There have been two homes at altitude (above 500 metres), that have a minor problem with misting. The misting is insufficient to condense and it dissipates during the day.

Will my windows comply with the standard 'AS1288'?

The “Glazing in Buildings” Standard AS1288 concerns itself with two things: Wind Loading and Human Impact Safety.

  • Wind Loading: Will the windows hold up against the winds expected in the setting in which they are being installed?One aspect of this is the thickness of the glass versus the area of the glass. The bigger the area the thicker the glass required. The higher the wind rating of the area the thicker the glass required.


  • Human Impact Safety: If a person impacts the glass with speed or force, will it break and damage the windows or themselves?Again, this goes towards the thickness of the glass, particularly of low-to-the-ground glazing and in the case of wet areas, it is about using Grade A safety glass.The glazing standard has been significantly improved over the last few years, so many homes may not have compliant glazing. Adding ecoGlaze® will enhance the safety of your windows because the acrylic panel that is added internally is almost unbreakable. It won’t break due to impact from inside your home.
How much mess or interruption can I expect during a professional installation?

Due to the pre-production in our factory, installation is quick and tidy. Our installers are incredibly conscientious when working in your home and have a long-standing reputation for leaving every home clean and tidy. There is no damage to your windows or surrounds and no re-plastering or painting is necessary.

How long will it take to install?

We recommend you allow approximately one hour per window pane. A whole home can be retrofitted with the ecoGlaze® Retrofit Double Glazing System within 1 to 2 days.

Is it possible to remove the ecoGlaze® system for cleaning or repainting?

Whilst it is possible to remove the ecoGlaze® Retrofit Double Glazing System from your windows for cleaning, it is not usually required. However, if you wish to repaint your window frames, the timber mouldings held firmly to the window frame with invisible magnets make removing the acrylic panel a simple task.

What happens if the acrylic gets scratched?

The ecoGlaze® acrylic panel is strong and durable. Light scratches can be polished out with a soft cloth and Silvo. If the damage is severe, because the panel is separate from the timber moulding, it is a simple and relatively inexpensive process for our installers to cut and fit a new acrylic panel to replace the damaged panel.

What about safety with children and pets?

If a child or pet impacts with a regular pane of glass, the results can be tragic.  Fitting ecoGlaze® to the internal window will enhance the safety of your home because the acrylic panel that is added is almost unbreakable. It won’t break due to impact from inside your home, making your home much safer for even the most boisterous child or pet.

Is ecoGlaze available for skylights, glass roofs or atriums?

The ecoGlaze® Retrofit Double Glazing System is not suitable for sloping glass roofs or atriums.