What Are Double Glazed Windows?

When people search “what are double glazed windows”, they are really asking how two panes of glass can make a house quieter, more comfortable and more energy efficient. In simple terms, double glazed windows are glazed windows that use two panes of glass separated by a sealed gap to create a thermal barrier between your home and the outside world.

Instead of a single pane of glass, double glazed windows use two glass panes, often with an insulating gas in between, to significantly reduce heat transfer and noise pollution. They are now some of the best windows for modern Australian homes, and they are increasingly common in newer constructions and performance focused renovations.

As an independent directory, Trade Heroes works with experienced double glazing specialists across Australia. This guide explains how double glazing works, how double glazed units are built, the main benefits of double glazed windows and what to look for when you are choosing double glazed windows for your own house.

What Does ‘Double Glazed’ Mean?

Double glazed means the window uses two panes of glass instead of just one, with a sealed gap between them that improves insulation and reduces noise. That gap changes how heat and sound move between indoors and outdoors, which is why double glazing products perform so differently from single glazing.

If you look at double glazed glass from the edge, you will see two panes of glass separated by a spacer bar, with the space in between typically filled with dry air or an inert gas such as argon gas. This simple change in window glazing makes a big difference to energy efficiency and comfort.

Basic Definition Of Double Glazing

Double glazing is a type of window glazing where two panes of glass are sealed together with a gap in between to form an insulated glass unit. That unit is then installed into a window frame or door frame.

Key points of what double glazed windows are:

• Double glazed windows consist of two layers of glass instead of just one single pane
• The glass separated by a gap creates a thermal barrier that slows heat loss and heat gain
• That same gap helps double glazing reduce noise, because sound waves are dampened as they cross between panes
• Double glazed units are designed to provide better thermal insulation and noise reduction than single glazed windows

Because the insulated glass is manufactured as a sealed unit, these energy efficient windows are consistent, reliable and easy to specify across a whole house.

Key Parts Of A Double Glazed Unit (Glass, Spacer, Air Or Gas Gap, Seals)

A modern double glazed unit is made up of several parts that work together to deliver improved insulation and noise reduction.

The main components are:

• Panes of glass
• Two panes of glass, often called two glass panes or two panes of glass. These may be clear glass, low E glass, toughened glass, laminated glass or tinted glass depending on the job.
• Spacer bar
• A rigid spacer bar runs around the edge, keeping the panes of glass separated at a consistent distance. This creates the space in which the insulating gas or air sits.
• Gap typically filled with air or gas
• The gap is typically filled with dry air or an insulating gas such as argon gas or another inert gas. This insulating gas improves insulation and helps create a more effective thermal barrier.
• Seals
• Perimeter seals keep air and moisture out and hold the gas inside. Good seals are critical to the long term performance of double glazed units.

Together, these elements form insulated glass units that are then built into complete windows and doors.

How Double Glazed Windows Are Constructed

Double glazed windows are constructed as insulated glass units placed inside frames made from materials such as uPVC, aluminium, timber or composites. The combination of the IGU and the window frames gives double glazed windows their superior insulation properties.

Insulated Glass Units (Igu S)

Insulated glass units are the heart of double glazed windows. An IGU is a factory built assembly where two panes of glass are separated by a spacer bar, the space is dried, typically filled with air or gas and then sealed.

In practice:

• The glass panes are cut and cleaned
• The spacer bar is fitted to create the correct space between panes
• The cavity is dried and then typically filled with air or an insulating gas
• The edges are sealed to create a long lasting, airtight and watertight insulated glass unit

These insulated glass units are then installed into window frames and door frames to create complete windows and doors.

Air Filled Vs Gas Filled (Argon, Krypton)

The space in double glazed units can be filled with either dry air or an inert gas such as argon or krypton. Both options improve insulation compared to single glazing, but gas filled IGUs can deliver improved energy efficiency.

At a glance:

• Air filled units
• Use dry air between the panes. These still provide improved insulation and noise reduction over single glazing and suit many homes.
• Argon gas filled units
• Argon is an inert gas that conducts less heat than air. When double glazed units are filled with argon gas, they can significantly reduce heat flow and improve energy efficiency.
• Krypton gas filled units
• Krypton is used in some high performance products or where a thinner space is required. It can provide very good insulation in a compact gap.

Some homeowners worry that gas will leak out quickly. In reality, quality double glazing products are designed so that any gas loss is very slow and performance remains high for many years when you install and maintain them properly.

Frames And Materials (Upvc, Aluminium, Timber, Composites)

The window frame matters just as much as the glass. If the window frame conducts heat or lets in draughts, you will not get the full benefits of double glazed windows.

Common frame options are:

• uPVC frames
• Provide improved insulation and low maintenance. They resist humidity, corrosion and warping and are popular in cold climates as well as mixed climates.
• Aluminium frames
• Strong and slim but naturally conduct heat well, so energy efficient windows usually use thermally broken aluminium, which includes an insulating strip within the frame to reduce heat transfer.
• Timber frames
• Offer natural insulation and a warm appearance. They need more maintenance but can be appropriate in heritage homes and architectural projects.
• Composite frames
• Combine materials, for example timber inside and aluminium outside, to balance durability, insulation and appearance.

Suppliers listed on Trade Heroes work across these frame systems, so when you are choosing double glazed windows you can match the window frame and glass to your climate, style and budget.

How Double Glazed Windows Work

Double glazed windows work by disrupting heat flow and sound waves as they pass between indoors and outdoors. Two panes of glass with a gap in between provide superior insulation properties compared to a single pane.

Thermal Insulation And The Gap Between Panes

The gap between panes acts as a thermal barrier that slows heat transfer between warm and cold air. Because the glass separated by space and insulating gas does not transfer heat as quickly, your home’s energy efficiency improves.

In winter, double glazing helps keep warm air and heating energy inside and cold air outside. In summer, double glazing helps keep cool air from your air conditioner indoors and reduces heat gain from the outside world. This is how double glazed windows can maintain a more stable indoor temperature in both hot and cold climates.

By slowing heat flow through the glass, double glazed windows can decrease a home’s heat loss or gain by almost 30 percent compared to single glazing. Actual results vary depending on climate, house design and other insulation, but the effect on comfort and energy consumption is noticeable.

Reducing Heat Transfer (Conduction, Convection, Radiation)

From a simple science point of view, double glazing reduces heat transfer in three ways: conduction, convection and radiation.

• Conduction
• Heat conduction is heat flowing through solids. In single glazing, heat passes straight through one pane of glass. In double glazed windows, heat must pass through two panes and a gap, which significantly reduces heat transfer.
• Convection
• Convection is heat moved by moving air. In the narrow space between two panes of glass, air or insulating gas cannot circulate easily, so there is less convective heat transfer between inside and outside.
• Radiation
• Radiant heat is energy from the sun or warm surfaces. Many modern double glazed windows use low E glass with a low emissivity coating that reflects some radiant heat back to where it came from and blocks some harmful UV rays. This reduces unwanted solar heat and helps manage heat loss in winter.

By tackling all three forms of heat transfer together, installing double glazed windows improves insulation and can reduce reliance on artificial heating and cooling.

How Double Glazing Helps With Noise Reduction

Double glazing also provides significant noise reduction because sound waves are disrupted as they cross multiple layers. In single glazed windows, outside noise passes easily through one pane. In double glazed windows, sound waves must cross two panes and the space between them.

The effects are:

• The first pane absorbs and reflects part of the noise
• The insulating gas or air between panes dampens sound waves further
• The second pane blocks more of what is left

Double glazing can significantly reduce noise pollution and reduce noise from traffic, neighbours and other sources. In many cases, double glazed windows can block outside noise up to 60 percent more than single glazed windows and can make homes feel much quieter to the people living inside.

For homes in busy areas, double glazing reduce noise and improve everyday comfort. Trade Heroes specialists regularly install double glazing in homes near main roads, rail lines and schools for this reason.

Double Glazing Vs Single Glazing

Double glazing and single glazing look similar at a glance, but they behave very differently. Understanding the differences helps you weigh up performance and overall cost.

Key Differences In Structure

Single glazed windows use one pane of glass, while double glazed windows use two panes of glass separated by a spacer bar and sealed to create an insulating gap.

Single glazing:

• Uses one piece of glass
• Offers basic protection from weather but limited insulation
• Is common in older houses and budget windows and doors

Double glazing:

• Uses two panes of glass in each unit
• Has the glass separated by a space that is typically filled with air or insulating gas
• Uses sealed insulated glass units for better insulation and noise reduction
• Is becoming increasingly common in newer constructions due to superior insulation properties

Because of the extra materials and manufacturing steps, double glazed windows are typically more expensive than single glazed windows. However, they can save money over time through lower power bills and better comfort.

Performance Differences (Temperature, Noise, Condensation)

Performance is where double glazing clearly outperforms single glazing. Double glazed windows significantly reduce heat transfer and noise infiltration compared to single glazed windows.

Main performance differences:

• Temperature and comfort
• Double glazed windows are more effective at keeping heat in or out than single glazed windows. They help maintain comfortable indoor temperatures year round by reducing heat loss in winter and heat gain in summer.
• Energy bills and energy costs
• Because of improved insulation, double glazing can save up to 20 percent more on energy bills compared to single glazed products. Double glazed windows can also help reduce reliance on heating and cooling, which lowers energy costs and power bills over time.
• Noise
• Double glazed windows can significantly reduce noise pollution, making them ideal for homes in busy areas. They reduce noise from the outside world more effectively than single glazing and can help reduce noise pollution inside your house.
• Condensation
• Double glazing can reduce the likelihood of condensation forming on windows by keeping the interior glass pane closer to room temperature. This helps protect frames and finishes and reduces mould risk.
• Strength and security
• Double glazed windows are less likely to break than single pane windows because there are two layers of glass. This added strength and the difficulty of breaking through two panes improves home security.

Single glazed windows still appear as a budget option and in some older buildings, but for most modern homes, double glazing is the more sensible long term choice.

Types Of Double Glazed Windows

Double glazing is a glazing system that can be applied to many styles of windows and doors. You are not limited to just one look or opening type.

Fixed, Sliding, Awning, Casement And Other Styles

Most common window styles can be built as double glazed windows. When you are choosing double glazed windows, you can match the style to your home.

Popular styles include:

• Fixed windows
• Do not open and are often used where you want a view and maximum insulation.
• Sliding windows
• A very common style in Australian houses. Two panes or more slide past each other in a horizontal window frame.
• Awning windows
• Hinged at the top and open outward from the bottom, allowing ventilation even when it is raining.
• Casement windows
• Hinged at the side and open like a door. They can provide very effective sealing when closed.

Double glazed windows are also available in various configurations so you can match the size and shape to your existing openings.

Low E Coatings And Specialised Glass Options

Within double glazed units, you can specify different types of glass to fine tune performance. This is where choices like low E glass and tinted glass become important.

Common options are:

• Low E glass
• Has a special low emissivity coating that improves energy efficiency, blocks some UV and helps manage heat loss and heat gain.
• Tinted glass
• Reduces glare and solar heat, useful on exposed elevations in hot climates.
• Laminated glass
• Adds a safety interlayer and can improve noise reduction and security.
• Toughened glass
• Stronger than ordinary glass and breaks into small pieces for safety. Often required in doors and low level glazing.

These options mean you can tailor double glazing products to your climate and the orientation of each window.

Double Glazed Doors And Other Applications

Double glazing is also common in windows and doors such as sliding doors, French doors and other glazed doors. Anywhere you have large panes of glass, double glazing can help with insulation and reducing noise.

Common applications include:

• Sliding glass doors for patios and balconies
• Hinged doors with double glazed glass panels
• Stacking and bi fold doors in open plan living areas
• Glazed sidelights next to entry doors

Treating your windows and doors as one system with double glazing helps you get consistent performance around the whole house.

Where Double Glazed Windows Are Commonly Used

Double glazed windows are widely used in new homes and in retrofits, especially in regions with volatile weather conditions or higher noise levels. They are suitable for both hot and cold climates and for mixed climates between.

New Builds Vs Retrofits

In new builds, double glazed windows are often specified from the start as part of an energy efficient design. Because frames, openings and insulated glass units are planned together, you can get very good performance and a consistent look.

In existing homes:

• Installing double glazed windows can be done as a staged retrofit, starting with the rooms that suffer most from heat, cold or noise
• Secondary glazing can sometimes be used where full replacement is not practical, especially in heritage window frames
• Overall cost will vary depending on the size and type of windows, the number of openings and the installation company

In Australia, the cost of double glazed windows can vary depending on size, type and installer, but on average they often range between about $600 and $1,200 per window. Installation quality is a major factor in both the cost and the long term performance.

Homes In Hot, Cold And Mixed Climates

Double glazing is suitable for homes in hot climates, cold climates and all the mixed climates in between. The way you specify it will vary depending on orientation and local conditions.

Broadly:

• In cold climates, double glazing helps hold heat in and keep cold air out, reducing heating needs in winter
• In hot climates, double glazing reduces unwanted heat gain and helps keep cool air inside, reducing cooling costs in summer
• In mixed climates, double glazing smooths extreme temperature swings, so your house feels more comfortable year round

Research from organisations such as the Lawrence Berkeley National Laboratory has shown that energy efficient windows can significantly reduce energy consumption in residential buildings. By using double glazing as part of an efficient building envelope, you improve your home’s energy efficiency and comfort.

Benefits Of Double Glazed Windows (In Brief)

The main benefits of double glazed windows are comfort, energy efficiency, reducing noise, security and increased property value. While the exact results vary depending on the house and climate, the main benefits are consistent.

Comfort And Energy Efficiency

Double glazed windows can significantly improve comfort and energy efficiency compared to single glazed windows. By providing improved insulation and a strong thermal barrier, double glazing reduces heat loss and heat gain and helps maintain a more stable indoor temperature.

Key comfort and energy benefits include:

• Improved insulation and reduced heat transfer through windows and doors
• More stable temperatures across seasons, with less reliance on heating and cooling
• Improved energy efficiency and lower energy consumption, which can save money on energy bills and power bills
• Double glazed windows can decrease a home’s heat loss or gain by almost 30 percent and can save up to 20 percent more on energy bills compared to single glazed products when installed and specified correctly

By reducing energy costs and improving the performance of your house, double glazing helps lower your carbon footprint as well.

Noise Control And Condensation Reduction

Noise reduction and reduced condensation are two of the main benefits of double glazed windows that homeowners notice quickly. Double glazing can significantly reduce outside noise and reduce condensation on cold mornings.

Benefits include:

• Double glazed windows help reduce noise pollution by blocking more outside noise than single glazing
• They can significantly reduce sound waves from traffic, neighbours and other external sources
• They help keep the interior glass pane closer to room temperature, which reduces condensation in winter
• Less condensation means less moisture damage and less mould around windows

For homes in noisy streets or volatile weather zones, these benefits of double glazing are often just as important as the energy savings.

Security And Property Value

Double glazed windows can improve home security and increase property value. Two layers of glass and modern hardware make windows and doors harder to force or break than older single glazed systems.

Security and value benefits include:

• Double glazed windows are less likely to break than single pane windows because of two layers of glass
• They improve security by making it more difficult for burglars to break in quickly
• Energy efficient windows are attractive to buyers who value comfort, insulation and lower energy bills
• Double glazing can increase a home’s property value because buyers understand the benefits of double glazed systems and often look for these features in newer constructions

When you combine all these benefits of double glazed windows, the main benefits are clear: better comfort, lower energy costs, reduced noise, stronger security and an uplift in perceived quality.

Key Points To Consider Before Choosing Double Glazing

Choosing double glazed windows is about more than just picking two panes of glass. You need to consider orientation, climate, frame type, glass type, installation quality and overall cost.

Window Orientation And Climate

Orientation and climate should guide where you prioritise double glazing and how you specify glass. The impact of heat, cold and noise will vary depending on where each window sits.

Practical tips:

• Focus on west and north facing windows in hot climates where heat gain is a problem
• Pay close attention to large glazed windows on exposed sides in cold climates where heat loss is an issue
• Consider local climatic conditions, shading, ventilation and other insulation together with double glazing for best results

The performance of double glazed windows will vary depending on how well these factors are considered at design and installation stage.

Frame Choice And Glass Specification

Frame choice and glass specification have a big impact on how double glazed windows perform. When choosing double glazed windows, consider:

• The type of window that suits your home style and needs, whether fixed, sliding, awning or casement
• The size of openings, as bigger windows can have more impact on comfort and need careful specification
• The quality of glass, including whether you use low E glass, laminated glass or tinted glass
• The type of window frame, as frame type affects durability, insulation and long term performance

Higher quality glass and frames may cost more upfront but can significantly reduce energy consumption and improve your home’s energy efficiency in the long term.

Installation Quality And Building Codes

Proper installation is crucial to enjoy the full benefits of double glazed windows. Even the best double glazing products will underperform if they are not installed correctly.

Before you install double glazing, make sure:

• Your installer is experienced and follows Australian standards and relevant building codes
• Windows are sized correctly and fitted squarely into openings
• Sealing is done carefully to prevent air leaks and water leaks
• You understand how choices will affect overall cost and long term performance

When you get these decisions right, installing double glazed windows can significantly reduce energy costs, reduce noise pollution, improve comfort and help your home save money and energy across many winters and summers.

If you are ready to move from research into action and want help finding the best windows and doors for your home, Trade Heroes can connect you with vetted specialists across Australia who install energy efficient double glazed windows and doors every day. Visit Trade Heroes today, find trusted local installers and take the next step toward a quieter, more comfortable and more energy efficient home.