What Are Double-Glazed Windows?

Windows play a big role in the energy efficiency of a home as they are responsible for up to 40% heat gain and heat loss. Double glazed windows help prevent that heat transference because they have two panes of glass instead of one with a hermetically sealed layer of gas. In this article we will guide you through what double glazed windows are, how they work, and how they can save you money and help the environment.

What Exactly is Double-Glazing on Windows?

When windows have double glazing, there are two layers of glass that are separated by a small gap, designed to reduce heat and noise flow. It is called double glazing because there are two panes of glass rather than one. Double glazing also includes a small gap filled with gas in between the two pieces of glass. The double panes and gas filled gap results in less heat transference and reduced sound waves.

How Do Double-Glazed Windows Work?

Double glazed windows work because of the science and engineering behind them. This type of window has three layers that are all sealed together in a frame. These three layers comprise an external glass pane, a gas filled space, and internal glass pane. The three layers are closed with a sealant and then installed into a window frame. This combination of three layers and an airtight window frame mean that energy (heat and sound) cannot pass through as efficiently as a single pane window.

The Three Layers

• External pane: The external pane is the first layer of protection from the elements including UV rays, cold air, rain, heat, wind and noise. Double glazed windows can be made of regular panes of glass or Low-E coated glass (Low Emissivity glass) which reduces the amount of radiation and transmission of heat, or cold, from the outside through to the inside.
• Air gap: There is an air gap between 6-12mm in double glazed windows that separates the two panes of glass. This air gap is filled with Argon gas and sealed inside to act as an insulator and slow the transference of heat from one side to the other. A spacer bar inside the unit keeps the window frames apart and is packed with desiccant to absorb moisture and prevent condensation.
• Internal pane: The internal pane is the final layer of the double glazed window. This second pane of glass, combined with the argon gas, external pane and fully sealed window, traps air inside the house and reduces the transference of heat and noise.

How Effective is Double-Glazing?

Double-glazing can have a drastic effect on energy efficiency and noise reduction by reducing the amount of transference through the window. Double glazing means less noise pollution and lower bills.

Statistics show that double glazing:

• Reduces the amount of UV rays by 75%.
• Improves the home’s energy rating assessment by up to 50%.
• Reduces noise by up to 40dB.

Double-Glazed vs Single-Glazed Windows

If you are trying to work out whether to install double-glazed or single-glazed windows, it is important to know the difference between the two. The type of windows you choose will have an impact on the home’s energy efficiency, bills, and noise level, and it is important to understand if it is worth investing in double-glazing.

The most obvious difference between the two is that single glazed has one pane of glass, while double glazed have two. Double glazed windows also have a further insulating factor with the gas filled air gap between the two panes of glass.

Single glazed windows are the old school windows you see in a lot of places. They are easy to install and don’t cost much money. However, their lack of insulation means more energy escapes through the windows leading to higher cooling and heating costs. Double glazed windows may be more expensive but the two panes of glass and air gap provide excellent insulation, reducing energy bills and noise transference.

Single glazed windows do not offer the same noise reduction as double-glazed counterparts. While double-glazed windows can reduce noise levels by up to 40dB, single-glazed windows provide a noise reduction of up to 27dB.

Benefits and Disadvantages of Double-Glazed Windows

Double-glazed windows are proven to reduce heat and noise transference when installed correctly. However, it is important to examine both the benefits and disadvantages to fully understand what double-glazed windows are.

Benefits:

• Save money on bills: By reducing the heat transfer in summer and winter, the house needs less cooling and heating which saves money on energy bills.
• Helps the environment: The decreased energy usage is good for the environment with fewer fossil fuels being burned and reduced carbon emissions.
• Reduced noise level: Double-glazed windows result in reduced noise level from inside and outside the building.
• Increased security: You have better security as it is harder to break through a double-glazed window as compared to a single window pane.

Disadvantages:

• Can cost more initially: Double-glazed windows can cost more upfront than single-glazed windows. However, the savings on energy bills will quickly recoup the initial investment.
• Can trap heat: Sometimes double-glazed windows can trap the heat which is good in winter but not in summer.
• Cannot be repaired: Double-glazed windows cannot be repaired. This is because, if broken, the argon gas may have escaped so the window will need to be replaced.

What To Look For When Choosing Double-Glazed Windows

When investing in double-glazed windows, here are some key factors to consider to help you choose the right type of window for your purposes.

• Understand your needs: Take into account your specific needs when choosing double-glazed windows. Consider the direction the windows are facing, the climate and outside noise.
• Type of glass used: You may want to consider Low-E glass which significantly reduces the amount of heat conducted through the window and lowers the heating and cooling bills.
• Frame material: The most common materials for frames are uPVC or aluminium, although timber frames are sometimes used. Each material has a different effect on the thermal performance of the window. uPVC is a sustainable and low maintenance framing material with excellent insulation capacity. Aluminium is strong and durable but not as efficient with sound and thermal insulation. Timber is a traditional frame but requires a lot more maintenance. Its sound and insulation properties are not as efficient as uPVC.
• Amount of space between the panes: For thermal efficiency, make sure there is at least 12mm space between the panes.
• What’s in between: Argon and Krypton are the main gases in between the panes of glass. When looking at the type of gas, argon gas is a noble gas that is a fantastic insulator and helps prevent buildup of frost and condensation. It is also non-toxic. Krypton is denser than argon but it costs more.
• Window style: There are many different styles of double-glazed windows to choose from, including fixed, awning, tilt and turn, and bay windows. The style you choose will depend on the type of home you have, climate and location.
• Cost: The cost of double-glazed windows will vary depending on factors like the frame material, glass type, window style and number of windows. It is important to weigh up the initial cost and then factor in the long term savings with significantly reduced power bills.
• Weight: Double-glazed windows and their frames are often heavier than single-glazed windows. Before you choose the windows, make sure the area around the window will be strong enough to support it.
• Installation: It is highly recommended that double-glazed windows are installed by a professional to make sure the job is carried out properly. A qualified window installer understands how to plan ahead to ensure the window installation runs smoothly. Professional installation ensures the ultimate in energy efficiency and noise reduction.

Double-glazed windows are windows with two panes of glass and a gas filled space in between, designed for maximum energy efficiency and sound reduction. When you choose double-glazed windows, you have a significant impact on your home’s energy efficiency. In order to help you choose the right type of window for your home, we have explained exactly what double glazing is, benefits and disadvantages, and what to consider when choosing double-glazed windows. For further information, the experts at Windows for Life are always on hand to offer advice.