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Triple glazed windows have become increasingly popular among homeowners and property developers in recent years. Their high-performance properties allow them to provide excellent insulation, reducing energy loss and keeping heating bills low. However, when choosing triple glazed windows, it is crucial to pay attention to their U-values. In this article, we will explore what a good U-value is for triple glazed windows, and what factors affect it.

What is a U-value?

A U-value is a metric used in construction to measure how well a material can insulate against heat loss. It represents the amount of heat transferred through a material per square meter per hour, given a temperature difference of one degree Celsius between the inside and outside of the building. The lower the U-value, the better the insulation.

U-values are essential for windows, doors, and other building elements that separate the inside and outside of a building. They measure the energy efficiency of these elements and can help you choose the most efficient materials for your property.

What is a good U-value for triple glazed windows?

The U-value of triple glazed windows varies depending on the manufacturer and the insulation materials used. However, a typical U-value for triple glazed windows ranges between 0.8-1.3 W/m²K. A U-value of 0.8 W/m²K would be considered excellent, indicating the triple glazed windows have high energy efficiency and minimal heat loss.

While it's good to aim for a low U-value, it's also important to consider the cost and other factors, such as durability and sound insulation. Some manufacturers may offer windows with lower U-values, but they could be more expensive, making them less practical for the average homeowner.

Factors that affect the U-value of triple glazed windows

Several factors affect the U-value of triple glazed windows, including the type of glass, frame material, and gas fill used. Let's explore each of these factors in more detail:

1. Glass type

The type of glass used in triple glazed windows greatly affects their U-value. Low-emissivity (Low-E) glass is the most common type owing to its excellent insulating properties. Low-E glass has a special coating that reflects heat back into the room, reducing heat loss. It also allows natural light to enter the room, which is a desirable feature for many homeowners.

2. Frame material

The frame material used to build triple glazed windows also affects their U-value. Some materials, such as uPVC, timber, and aluminium, are better insulators than others. For example, uPVC frames have excellent insulating properties and are incredibly durable, making them a popular choice for many homeowners.

3. Gas fill

Triple glazed windows are filled with gas that acts as an insulator. Common gas fills include Argon and Krypton, which are denser than air and can improve insulation. These gases are non-toxic, non-flammable, and have excellent insulating properties, increasing the window's energy efficiency.


A good U-value for triple glazed windows is below 1.3 W/m²K, with a value of 0.8 W/m²K indicating excellent energy efficiency. However, it's essential to understand that these values are not the only factors to consider. The type of glass, frame material, and gas fill used are equally important in determining the insulating properties of a triple glazed window. Ultimately, a good triple glazed window should provide energy efficiency, durability, and sound insulation, making it a valuable addition to any home.