Understanding U-Values and Its Importance in Window Selection
16th February 2023
Are You Choosing The Right Product?
When it comes to energy-efficient windows, you may have heard the term "U-value" being used. U-value is a measure of how well a window can prevent heat from escaping or entering a building. However, it's important to understand that U-values in Australia are different from those in Europe, and they can't be compared directly. This means that when purchasing windows for your project, you can't use European U-values in place of Australian U-values.
Australian U-values are calculated based on the Australian Standard AS/NZS 4859.1:2018. This standard provides the method for calculating the U-value of a window or door. The U-value calculation takes into account factors such as the thermal conductivity of the frame, glazing, and any spacers used between the glass panes. The U-value of a window or door is expressed in watts per square meter per Kelvin (W/m2K). The lower the U-value, the better the window or door is at preventing heat loss or gain.
In Europe, U-values are calculated using the EN ISO 10077-1 standard. This standard is similar to the Australian Standard, but there are some differences in the way U-values are calculated. For example, the European standard uses a different temperature difference between indoor and outdoor temperatures than the Australian standard. This means that a U-value calculated using the European standard may not be directly comparable to a U-value calculated using the Australian standard.
Another factor to consider is that European U-values are often given as centre-of-glass values, while Australian U-values are typically whole-window values. This means that the European U-value only takes into account the thermal performance of the glass itself, whereas the Australian U-value considers the thermal performance of the entire window, including the frame and any spacers.
It's important to use Australian U-values when purchasing windows for your project because they take into account the unique climate and environmental conditions in Australia. Using European U-values instead can lead to windows that are not properly designed for the Australian climate, which can result in poor thermal performance and increased energy costs.
Unfortunately, many Australian companies are not aware of the differences between Australian and European U-values and may promote the wrong information. This can result in confusion for consumers and potentially lead to the installation of non-compliant and inefficient windows.
In addition, using European U-values instead of Australian U-values can result in non-compliance with Australian building regulations. Australian building codes require that windows and doors meet specific energy efficiency standards, and compliance with these standards is determined using Australian U-values.
In summary, while U-values are an important factor to consider when purchasing energy-efficient windows, it's crucial to understand the differences between Australian U-values and European U-values. Australian U-values are calculated based on the unique climate and environmental conditions in Australia and take into account the entire window system, whereas European U-values are calculated using a different standard and typically only consider the thermal performance of the glass. Therefore, it's important to use Australian U-values when purchasing windows for your project to ensure compliance with Australian building codes and to achieve optimal energy efficiency.
For more information on WERS (Window Energy Rating Scheme) click HERE.