1300 RETROFIT (738-763)
REQUEST A QUOTE
REQUEST A QUOTE
1300 RETROFIT (738-763)

How Retrofit Double Glazing Windows Create A More Comfortable, Quieter Home

Retrofit Double Glazing Windows Create A More Comfortable, Quieter Home

How Retrofit Double Glazing Windows Create A More Comfortable, Quieter Home

Posted on in Blog

Retrofitting your windows is one of the smartest ways to improve your home’s comfort, without undergoing the cost or disruption of full window replacement. In Australia, where cold winters and hot, dry summers are part of life, energy efficiency and noise reduction are increasingly important to homeowners.

But when it comes to double glazing, it’s not a one-size-fits-all solution. In fact, there are two common approaches to window retrofitting on the market today. Each method offers unique benefits and suits different types of homes, window frames and performance goals.

Here’s what you need to know if you’re comparing retrofit options and want to make an informed choice.

Understanding the Two Retrofit Double Glazing Methods

1. Secondary Glazing (Used by Magnetite)

This method involves adding a new set of windows to the inside of your existing windowsill, allowing air cavity between the two windows. The air cavity between the original window and the new secondary window acts as a barrier to improve both thermal and acoustic windows insulation.

Because the existing window is left intact, this solution is perfect for homeowners who are unable to replace or want to preserve their existing windows especially in heritage homes and strata properties.

 

2. In-Frame Glass Replacement with IGUs

The second approach involves removing the original single-pane glass and replacing it with an insulated glass unit (IGU), a sealed unit of two glass panes, sometimes filled with argon gas. This method may require a modification to the original window frame, usually timber, to accommodate the thicker double-glazed unit.

It’s a more traditional approach that replicates the look and function of modern double glazing and it tends to focus primarily on thermal performance.

 

Thermal Comfort vs. Acoustic Windows Insulation

While both systems offer improved insulation, the results differ depending on the method and material.

  • Secondary glazing can create an air gap that is often wider than standard IGUs. Combined with the use of optical-grade acrylic (which transmits less sound than glass), this wider cavity significantly improves noise reduction, making it ideal for homes in busy suburbs, near airports or close to construction zones.
  • IGU replacement offers thermal performance by upgrading the existing glass itself. However, since both panes are glass and the cavity is typically smaller, the acoustic benefits may be more modest particularly if the windows are small or tightly fitted.

Window Type Matters

A key difference between the two methods is the type of window frame they work best with.

  • Secondary glazing can be applied to almost all types of windows including timber, aluminium, steel or even sliding and sash windows. It’s also suitable for architecturally sensitive homes or strata properties where window replacement is not permitted or practical.
  • IGU retrofits may require existing frame to be modified, sometimes extensively, to hold the thicker glass unit. This limits compatibility and may not be an option for metal-framed or heritage windows without significant alterations.

Aesthetic and Structural Considerations

Because secondary glazing is installed on the interior of the window reveal, it preserves the external appearance of the home, especially important in character homes where council guidelines or building covenants are in place.

On the other hand, the IGU method alters the original frame and replaces the visible glass. While this can result in a “cleaner” look from the inside, it could also change the proportions or appearance of traditional window designs.

Cost and Installation Time

In most cases, retrofit double glazing is more cost-effective than replacing single-pane glass with IGUs. It also offers faster, less intrusive installation, often completed in a matter of hours per window, with minimal mess or disruption to your home.

In contrast, IGU installation can involve routing timber, reglazing and sealing, all of which add labour and material costs.

A Case Study

We’ve seen firsthand how homeowners across Australia make decisions based on their priorities. Some opt for IGU retrofits when thermal insulation in timber windows is their main focus. Secondary glazing provides enhanced acoustic insulation and energy efficiency, making it ideal for homeowners in busy areas or along main roads. It’s also versatile and easy to install.

One homeowner in eastern Adelaide wanted to reduce their heating bills in winter but was also struggling with early-morning traffic noise. Their home featured aluminium sliding windows, so an IGU retrofit wasn’t feasible. Our team installed Magnetite’s retrofit double glazing and the results were immediate: quieter mornings, warmer rooms and lower energy use, all without changing the look of the windows.

What’s the Best Retrofit Option for You?

Ask yourself these questions to determine the best fit:

  • Do I want to reduce noise as well as heat loss?
  • What type of window frames do I have—timber, aluminium or steel?
  • Am I trying to preserve the appearance of my home’s façade?
  • Is this a heritage-listed or strata-regulated property?
  • Do I want a faster, more affordable installation process?

 

If your windows are timber-framed and you’re primarily after thermal comfort, an in-frame IGU upgrade may be worth exploring. But if acoustic comfort, versatility and non-invasive installation are high on your list, Magnetite’s secondary glazing system is hard to beat.

There’s more than one way to improve the performance of your windows, but knowing the pros and cons of each system can help you make the right call for your home. Whether you’re trying to stay warm in winter, cool in summer or block out the constant hum of city life, double glazing offers real benefits but the method matters.

At Magnetite, we offer a smarter, more flexible solution that’s tailored to your needs, your window type and your lifestyle. And with our retrofit double glazing, you get comfort, energy savings and peace and quiet, all without replacing your windows.

Book a free in-home assessment today and see why thousands of Australians trust Magnetite for smarter window insulation.

  1. Conduction
    Heat moving through an object (i.e. heat will travel through an aluminium, or steel frame more easily than through a timber or PVC frame).
  2. Radiant heat
    Heat from the direct sun. It can pass through space until reflected or absorbed.
  3. Convection
    Heat flow resulting from air movement e.g. either 'natural' convection - warm air rises, or 'forced' convection - a breeze by a window, both can result in a draught by a window.
  4. Infiltration
    Air leaks around the frame, around the window sash and through the gaps in the movable window parts.

When evaluating your options to improve the thermal performance of your windows, the following double glazing key performance criteria should be considered:

  • U-Value (Uw) represents heat transfer through a window, irrespective of direct sunlight. The lower a window’s U-Value, the better the insulation performance.
  • Solar Heat Gain Coefficient (SHGC) measures the solar energy that passes through glazing. The lower the SHGC, the less solar heat is transmitted through a window.
  • Air Infiltration or leakage measures the rate at which air passes through gaps in window joins and seals. The lower the air infiltration, the better a window’s energy performance.

The Window Energy Rating Scheme (WERS) Thermal Performance

Aluminium Frame Windows

Glazing Type Cooling Stars Heating Stars Cool% Heat% Uw SHGC
Single glazed 3mm clear glass* half blue star red starhalf red star 7.4 0.77
Single glazed 3mm clear glass &
4.5mm Magnetite		 blue starblue starhalf blue star red starred starred starred starred starhalf red star 35% 59% 2.9 0.67

Timber Frame Windows

Glazing Type Cooling Stars Heating Stars Cool% Heat% Uw SHGC
Single glazed 3mm clear glass* blue starhalf blue star red starred starred starhalf red star 20% 28% 5.5 0.69
Single glazed 3mm clear glass &
4.5mm Magnetite		 blue starblue starhalf blue star red starred starred starred starred starred star 37% 61% 2.6 0.66
Single glazed 3mm clear glass with
Solartite** and 4.5mm Magnetite		 blue starblue starblue starblue starblue starblue starhalf blue star red starred starred starred starhalf red star 76% 45% 1.8 0.20

 

*WERS standard typical industry window
**Solartite is a range of high performance window film. The window tested above has Solartite’s low-e film.

Magnetite vs Traditional Double Glazing – What the experts says

Winter - the ideal situation is to let in as much of the sun's heat and then trap it inside to maintain a comfortable environment in your home or office. This will also significantly reduce heating costs and saves you money. The ideal window for winter will have a high SHGC to let the sun's heat in and a low U-Value to prevent the heat from escaping. Clear windows without shading films are better suited for winter climates.

Compared with traditional double-glazing, Magnetite’s double-glazing solution can provide better results during winter or for cold climate areas such as Canberra, the Adelaide Hills and Blue Mountains.

Magnetite's clear acrylic window panels allow the direct heat from the sun's rays to enter the building and once inside, Magnetite's superior magnetic seals retain the heat, giving Magnetite an advantage over conventional operating windows.

Glazing Type Cooling Stars Heating Stars Cool% Heat% Uw SHGC AI
Double Glazed 3mm clear glass/12mm air
gap/3mm clear glass IGU (Insulated Glass Unit)*		 blue starblue starhalf blue star red starred starred starred starred starhalf red star 40% 55% 3.0 0.61 5.0
Single glazed 3mm clear glass &
4.5mm Magnetite		 blue starblue starhalf blue star red starred starred starred starred starred star 37% 61% 2.6 0.66 0.5

 

*WERS standard typical industry window

Summer - the ideal situation is to minimize the heat coming in from outside and prevent the cool air inside from escaping through the window. This will make your home more comfortable and reduce your air-conditioning costs. The ideal window for summer, or for a large west-facing window, will have a low SHGC to limit the heat from the sun's direct rays, as well as, a low U-Value to prevent the heat in the air outside from moving through the window and warming the cool conditioned air inside. It is better to have a shading film on the first (outer) glass pane to limit the heat that enters the double glazed unit.

The combination of Magnetite retrofit double glazing and Solartite outperforms the traditional insulated glass unit for hot climate. Magnetite fit over an existing window with reflective film will give better summer heat control than a double-glazed window with supertoned glass.

The Magnetite system stops the conduction and convection of heat better than glass windows giving superior results for summer conditions. Combined with a film or a shading device, Magnetite is the ideal solution for the hot Australian conditions.

Glazing Type Cooling Stars Heating Stars Cool% Heat% Uw SHGC AI
Double Glazed 5mm Supertoned glass/6mm
air gap/5mm clear glass IGU (Insulated Glass Unit)*		 blue starblue starblue starhalf blue star red starred starred starred starhalf red star 54% 425% 3.30 0.461 5.0
Single glazed 3mm glass Solartite**
and 4.5mm Magnetite		 blue starblue starblue starblue starblue starhalf blue star red starred starred starred star 73% 38% 2.4 0.19 0.5

 

*WERS standard typical industry window
**Solartite is a range of high performance window film. The window tested above has Solartite’s low-e film.

Click here to view pdf version of Magnetite WERS test result.

Noise Reduction Technical Data and Results

Proven Results

Noise pollution is one the biggest problems faced in the cities today, particularly in a high-density living. Unwanted noise can be responsible for sleep loss and lack of concentration. This can lead to a deterioration of health through increased stress levels, headaches, high blood pressure and loss of hearing.

Noise penetrates windows through leaky seals or vibrations through the window structure. To reduce noise, a window should minimise air infiltration, hold enough weight to limit vibration and allow a large air cavity. This cavity, or air gap, is the key to secondary glazing.

Expert Advice:

CSIRO Research by John Davy shown an air cavity can effectively enhance sound insulation performance. The larger the air cavity the more noise the window system can reduce. Results show a wide air gap of 100-125mm will improve sound insulation by an average of 7dB(A) more than windows with a narrow gap of 8-13mm.

Window or Glass Door Type Total Glass Thickness (mm) Air Cavity Thickness (mm) Sound Insulation (dB)
Single Glaze 3mm 3 0 23
Single Glaze 6mm 6 0 27
Double Glaze Narrow Gap 9-12 8-13 31
Double Glaze Wide Gap 9-12 100-125 38

 

The human ear is less sensitive to low frequency sound. According to a study released by the CSIRO, the human ear needs a change of 3dB to detect a difference in noise levels and the human ear perceives a change of 10dB as a doubling or halving of the noise level.

If you double the thickness of glass in a window the noise level will decrease by 3dB the least amount possible to make a difference. If the glass is laminated there is no perceived difference in noise reduction.

National Acoustic Laboratory Testing:

Working with the principles of noise transfer, Magnetite® and Soundtite are designed for high performance, which is achieved by combining air tight seals with the ability to maximize an air cavity and the flexibility to vary glazing thickness to suit. Magnetite® is excellent at reducing general noise such as busy roads, commuter trains and noisy neighbours. Whereas, Soundtite works well to combat low frequencies noise such as garbage truck, freight trains or airplane during take-off and landing.

Test Code Material Tested Rw* Improvement
ATF 707 (test window) Aluminium sliding window, 3mm float glass with mohair seals 23 N/A
ATF 709 Test window, 100mm air gap and Magnetite System (4.5mm acrylic panel) 35 52%
ATF 1507 Test window, 100mm air gap and Magnetite System (10.0mm acrylic panel) 39 70%
ATF 817 Test window, 100mm air gap and Soundtite (6.38mm laminated glass) 41 78%

 

*The Weighted Sound Reduction Index (Rw) is a measure for sound insulation performance of a single building element such as windows. The higher the Rw rating, the better the sound insulation.