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Double Glazed Windows in Sydney's Summer: Cool or Costly?

Double Glazed Windows in Sydney's Summer.

Double Glazed Windows in Sydney’s Summer: Cool or Costly?

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Sydney, renowned for its stunning harbour and vibrant lifestyle, also experiences scorching summer temperatures. As the mercury rises, the need for effective cooling solutions becomes paramount. Among the array of options, double-glazed windows have gained attention for their insulation properties.

But are they truly suitable for Sydney’s summer heat? Let’s delve into the facts.


The Sydney Summer Challenge: Statistics Speak

According to the Bureau of Meteorology (BOM), Sydney experiences average summer temperatures ranging from 18°C to 26°C, with occasional heatwaves pushing the mercury beyond 40°C. This demands cooling solutions that can efficiently tackle both moderate and extreme heat.

Also, residential energy consumption accounts for a substantial portion of the overall energy usage. According to the Australian Energy Market Operator (AEMO), the demand for electricity often spikes during hot summer days, largely due to air conditioning use. This raises concerns about the environmental impact and energy efficiency of cooling solutions.

The Australian government is now actively promoting sustainable practices to reduce carbon footprints. Double-glazed windows, by enhancing energy efficiency, align with these goals. The Australian Sustainable Built Environment Council (ASBEC) emphasizes the importance of energy-efficient buildings in achieving national sustainability targets.

Understanding Double-Glazed Windows

Double-glazed windows are constructed with two window panes separated by air or an inert gas layer, with the primary purpose of improving insulation. This design effectively curbs the exchange of heat between a building’s interior and the external environment. In regions with chilly climates, this characteristic is prized for its ability to trap warmth indoors. Nevertheless, when scrutinising their performance in Sydney’s scorching summers, a pressing question emerges: can they genuinely keep the indoor temperature cooler?

These windows’ capacity to create a temperature buffer by restricting heat flow inwards is well-documented. While double-glazed windows excel at conserving conditioned air, their effectiveness in reducing the effects of direct sun in the summer heat depends on various factors.

Double-Glazed Windows in the Sydney Context

If there is direct summer sun on a window then this needs to be addressed to effectively reduce heat gain.  If the Double glazed window is made using clear glass then this will allow direct sun to come through the window into the room. The heat will then be trapped in the room potentially causing the room to heat up. This is why double glazing is so effective in winter as the room can passively heat and the heat is retained.

In summer it is important to stop the direct sun’ s rays before it enters the room.  This is generally done by ensuring the double glazing is designed with a solar control film on the external layer of glass.  This will help to reflect some of the suns harsh heat.

Solar films by their nature are darker than clear glass.  This means that while some heat is reflected, heat is also absorbed into the solar coating. This warms the external glass and that heat can drift into the room.  If you place your hand on a window with solar film during summer you will feel the immense heat that has been absorbed.  Often an air conditioning system will need to work overtime to cool the tinted glass.  This is why tinting a single glazed window may not be the answer in summer.   The heat can still drift into the room from the windows surface.

This is where the superior insulation of double glazing finds its place.   By having a second window layer, with an air cavity, inside the external tinted layer, the heat flow inside is restricted and the heat will be more likely to stay outside and the window layer cooled by the breeze.

Upgrading existing windows for a cooler summer

Double-glazed windows are renowned for their insulation prowess, but their efficacy in Sydney’s summer heat hinges on correct design.

One standout in retrofit double-glazing solutions is Magnetite. This system utilizes optical-quality acrylic, boasting thermal efficiency up to six times greater than conventional glass. This not only elevates energy efficiency but also enhances safety and durability of the window.

Magnetite’s magnetic seals are the game-changer. They create an impeccable, airtight seal around your window frame, effectively blocking out scorching summer heat and preventing chilly drafts from sneaking in during winter. As a result, Magnetite stands out with the lowest air filtration rate among all secondary glazing options, ensuring your home remains comfortable all year round.

Solartite is a crucial design element for combating the summer sun. This range of solar control films compliments the retrofit double glazing to ensure optimum thermal efficiency for your existing windows. Solartite proves to be indispensable, especially in spaces where windows are directly exposed to the sun, providing a pragmatic solution for bolstering window insulation.

Connect with the experts at Magnetite Sydney today to explore the ideal solution for fortifying your windows and creating a more comfortable and energy-efficient living space.

  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.