A gas filling is a critical component of double-glazed windows and doors, significantly enhancing their thermal performance. In this article, we will explore the function of gas filling in double glazing and the different types of gases used.
How Gas Filling Enhances Double Glazing Performance
Creating a Thermal Barrier: The primary function of gas filling in double-glazed windows and doors is to create a thermal barrier. The space between the two glass panes is filled with gas, which acts as an insulator, reducing heat transfer between the interior and exterior environments.
Reducing Convection: Gas-filled double glazing also reduces heat transfer by convection. The gas filling slows down the movement of air between the glass panes, minimising the circulation of heat.
Minimising Heat Loss: Gases have lower thermal conductivity than air, transferring heat less efficiently. When used in double glazing, this property helps minimise heat loss during cold months and heat gain during warm months.
Common Gases Used in Double Glazing
Argon: Argon is the most widely used gas in double glazing due to its low thermal conductivity and cost-effectiveness. It is approximately 34% more insulating than air, making it an excellent choice for improving the thermal performance of double-glazed windows and doors.
Krypton: Another gas utilised in double glazing is krypton, which has insulating characteristics that are even superior to argon ones. Yet, due to its increased cost, it is used far less frequently and is more expensive. Krypton is most efficient when there is a small amount of space between the individual panes of glass, such as in triple glazing.
Xenon: Xenon is the gas used in double glazing less frequently than any other gas, although it provides the best level of insulation. Because it is expensive, it is often only used for specialist applications or windows with a high-performance level.
The Importance of Gas Retention in Double Glazing
For gas-filled double glazing to maintain its performance over time, it is crucial to ensure the gas remains within the sealed unit. Factors that can affect gas retention include:
- Quality of Seals: The seals around the glass panes must be high quality to prevent gas leakage over time. A well-sealed unit can maintain its insulating properties for 10 to 20 years.
- Professional Installation: Proper installation is essential to ensure the gas-filled unit remains intact and maintains its thermal performance.
Assessing the Energy Performance of Gas-Filled Double Glazing
When comparing different gas-filled double-glazed windows and doors, it’s essential to understand the energy performance metrics:
- U-Value: The U-value measures the heat transfer rate through the window or door. A lower U-value indicates better insulation.
- Solar Heat Gain Coefficient (SHGC): The SHGC measures the amount of solar heat that passes through the window or door. A lower SHGC indicates less heat gain during the warmer months.
- Air Leakage (AL): AL measures the air infiltration through the window or door assembly. A lower AL indicates better air tightness.
Gas filling plays a vital role in the thermal performance of double-glazed windows and doors, creating a thermal barrier that reduces heat transfer between the interior and exterior environments. Typical gases used in double glazing include argon, krypton, and xenon, each offering different insulation levels. Ensuring high-quality seals and professional installation is essential to maintain the insulating properties of gas-filled double glazing.