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Low E Glass vs Double Glazing: Which is Better?

Low-E glass and double glazing are two types of energy efficient window treatments that have many benefits, from reducing heating and cooling costs to blocking unwanted UV rays from entering your home. But what’s the difference between Low-E glass and double glazing? Let’s take a look.

Low E vs Double Glazing

What is Low E Glass?

Low-E glass, or low emissivity glass, is a type of specially coated window pane designed to reflect heat while allowing visible light through—essentially helping you save on energy costs without sacrificing natural daylight. It also helps block out damaging UV rays which can cause damage to furniture and fading of fabrics. Low-E coatings come in a variety of forms, but all are designed to maximize the amount of natural light coming in while minimizing heat loss in winter or gain in summer.

What is Double Glazing?

Double glazing consists of two panes of glass with an air gap between them in order to increase the insulation value of your windows. This air gap not only reduces heat transfer more effectively than single pane windows, but also minimizes sound transmission into the home for improved comfort levels inside. It’s important to note that the width of this air gap plays an important role in its effectiveness as it determines how much insulation is provided.

SGHC, Visible Transmission, U-value?

SGHC (Solar Glazing Heat Coefficient) – this measures the amount of solar radiation transmitted through the window. The lower the number, the more solar energy is blocked from entering the room.

Visible Transmission (VT) – this measures the amount of visible light that passes through a window, with higher numbers indicating better visibility.

U-Value – U value is the measure of the insulating capacity of the glass. This represents how quickly heat from hot air (not direct sunlight) will pass through the glass. The lower the U-value, the better insulation it provides against external weather conditions.

What do all these numbers mean when it comes to selecting the glass I need?

The numbers above can help you decide which window is right for your particular needs. For instance, if you need a window that provides insulation and blocks out solar radiation, then SGHC would be the most important factor to consider. On the other hand, if you want plenty of natural light with minimal heat transfer, then VT would be more important. The U-value of double glazing is generally lower than low E The U-value of double glazing is generally lower than low E glass, so it will provide better insulation against external elements. Ultimately, the numbers can help you determine which window is best-suited for your climate and preference. 

Low E glass - Viridian comfort plus performance
Example of performance - image shows the values for Viridian Comfortplus Low E Glass

So Which is Better? Double glazing or low E glass?

When it comes to energy efficiency, both Low-E glass and double glazing are great choices. However, the best window for your home will depend on your specific needs and climate. In some cases, Low-E glass may be more appropriate if you don’t need much insulation or are in a sunny climate; whereas if you need better insulation then double glazing would be the better choice. Ultimately, the decision should come down to which type of window can provide the most comfort while helping you save money in the long run.

Real World Examples

Sarah Thompson from Bondi Beach: Sarah, a resident of the breezy Bondi Beach suburb, was looking to replace her home’s windows to combat the intense sunlight and occasional chilly winds. After consulting with us, she chose Low-E glass. The primary reason was its ability to reflect heat while allowing ample natural light, perfect for her sunlit home. We didn’t advise Sarah to go for double glazing because, in her specific location, the primary concern was the sun’s intensity rather than insulation from cold, making Low-E glass a more suitable choice.

James and Lisa Mitchell from Parramatta: The Mitchells live in a bustling part of Parramatta and were keen on reducing both their energy bills and the noise from the streets. They opted for double glazing after our recommendation. The air gap in double glazed windows not only provided them with excellent insulation against varying temperatures but also significantly reduced the noise intrusion. While Low-E glass could have offered some energy efficiency, it wouldn’t have addressed their noise concern as effectively as double glazing did.

Amelia Rodriguez from Manly: Amelia’s sea-facing apartment in Manly often faced the brunt of salty sea winds, leading to rapid cooling in the evenings. She was inclined towards Low-E glass, but after our assessment, we recommended double glazing. The reason was its superior insulation properties, ensuring her home remained warm during cooler evenings. We believed that while Low-E glass would have been beneficial against the sun’s rays, it wouldn’t have provided the same level of insulation against the cold sea winds as double glazing.

Raj and Priya Kapoor from Chatswood: Living in a high-rise in Chatswood, the Kapoors were battling with both the summer heat and the glare from surrounding buildings. They decided on Low-E glass after our consultation. The special coating on Low-E glass helped in reflecting the heat and reducing the glare, making their living space much more comfortable. Double glazing, in their case, might have provided insulation, but it wouldn’t have been as effective in dealing with the specific challenges of heat and glare they faced.

Phillip Sharp
Phillip Sharp

Phillip Sharp has spent more than three decades honing his skills as a glazier in Sydney. He is currently employed at Splendid Window Glass Repairs, where he specializes in glass replacement and repair in the Sydney Eastern Suburbs area. With his wealth of experience and commitment to excellent craftsmanship, Phillip is highly respected in the industry and trusted by clients to provide top-quality work.