Energy Efficient Windows and Doors Explained



Energy efficiency. It’s the phrase on everyone’s lips. With rising power prices and increased awareness about the environmental impacts of generating electricity, consumers are investing in energy efficient solutions in every aspect of their lives.  But what does that mean when it comes to renovating and constructing homes and other buildings?


In the home, energy efficiency refers to the power used to light, heat, and cool the house, plus run any electrical appliances.

According to government figures, 40% of all the energy consumed in Australian homes is used for cooling and heating. So any solution that minimises the need for cooling or heating can substantially lower energy consumption (and power bills).

In general, such energy efficient solutions are designed to minimise heat loss when it’s cold, and heat gain when it’s warm.


Windows play a crucial role in heat loss and gain in the home.

It’s estimated that almost half of all heat loss during winter, and nearly 90% of heat gain during summer, can come from windows.

So if you’re looking to improve the energy efficiency of a home you’re renovating or building, you’ll want to look at the windows.

Energy efficient windows help to keep the warmth in during the colder months and keep it out during the warmer months. When selecting them, it’s essential to consider the design, glass type, glazing, and seals.

And if you’re a builder or architect, it’s important to know this information so you can make the right recommendations to your clients.


Toned glass – or “tinted” glass as it’s commonly called – restricts the entry of heat energy from the sun into a building.

This restriction is achieved because the raw glass includes metal oxides, and these metal oxides restrict solar radiation.

As a bonus, as the glass heats up, most of the heat it generates is released outside the building, not inside. So the home is kept cooler, and there’s less glare inside too.

Toned glass is especially suitable for homes in warmer climates where you want to keep the heat out.

Learn more about our Solar Block™ windows and doors.


Low-E glass has a very thin layer of metal or metal oxide coating on its surface.

“Low-E” stands for low emissivity. Low emissivity means minimal heat transfer.

In other words, low-E glass minimises heat entry and escape. That means its effective in keeping the heat in on colder days and keeping it out on warmer days.

As such, low-E glass is particularly suited to locations where heat gain and heat loss are equally concerning challenges.

Learn more about our Solar Comfort™ windows and doors.

Windows with IGUs

Commonly known as double glazed windows, “IGUs” (insulated glass units) have two or more panes of glass that are sealed with an air space between each layer.

This space and the additional pane of glass provide insulation against heat loss and heat gain.

Ideally, IGU windows should use toned or low-E glass to make them even more energy efficient. The best double glazed windows also have argon gas between each pane of glass, rather than just regular air.

Because they keep heat in and out, windows with IGUs are ideal for warm climates, cold climates, and mixed climates.

Learn all the benefits of double glazed windows and doors.

Windows with Thermal Breaks and IGUs

Thermal breaks and IGUs take the benefits of energy efficient windows to the next level.

In these windows, the aluminium frame is separated by a less heat-conductive material, such as polyamide. This “thermal break” reduces the heat transfer through the aluminium frame.

As is the case with a regular IGU window, an IGU window with a thermal break is most effective when it uses toned or low-E glass, and has argon gas in the space between each glass pane.

Windows with thermal breaks and IGUs are great for homes in every climate.

Learn more about our thermal break windows and doors.


A poorly sealed window allows warm air to enter and escape.

This negates some or all of the benefits from your window’s energy efficient design, which is where good weather seals come in. Because vinyl seals are prone to cracking, shrinking, and losing their shape, we recommend santoprene seals.


Two measures to look for when selecting energy efficient windows are U value and SHGC.

These measures apply to the whole window – including the glass, frame, and seals – not just the glass.

U value is a measure of heat transfer and loss. The lower the U value, the greater insulation the product provides against heat transfer and loss.

SHGC stands for solar heat gain coefficient, and measures how much solar radiation passes through the glass. The lower the SHGC, the less solar radiation passes through.

Find out more about energy ratings for windows and doors.


Of course, the same principles that apply to windows apply to doors.

Doors are a source of heat loss and heat gain in a house, much like windows.

And so you should be careful to look for the same characteristics and standards when selecting doors for your project.


So there you have it – now you know what to look for when selecting or recommending energy efficient windows!

By selecting windows with the right glass and design for your climate, you can ensure the house you’re building or renovating will save on power.

And as a bonus, when you save on power, you’ll be helping to protect the environment too.

Choosing the right windows and doors can be a challenge, especially if you’re new to the process. Our selection guideline will help you find the correct windows and doors for your project.


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Product availability, features, options, sizes, configurations and performance are subject to regional variations, design requirements, and building codes. Images are for illustration purposes only and may not accurately represent the product. Bradnam’s Windows & Doors reserves the right to change, alter or delete any aspect of this product without notice. We recommend visiting a Bradnam’s showroom before ordering to view colour swatches, glass samples and actual products.