The simple and straightforward answer is: No. The spacer bars of insulating glass are not necessarily the larger the better, but there is an optimal and scientifically calculated range.
The relationship between the main mode of heat transfer and the spacer bars
The heat insulation principle of insulating glass mainly involves using dry, still air or inert gases (such as argon) to block heat transfer. There are three ways for heat to be transferred through insulating glass
Heat conduction and convection: Transfer through the gas in the middle layer.
Thermal radiation: Radiating heat directly through the glass.
The width of the spacer bar mainly affects heat conduction and convection.
The "golden curve" of spacer bar width and thermal insulation performance
The relationship between the thermal insulation performance of insulating glass (K value /U value, the lower the better) and the thickness of the cavity is a curve that first drops sharply, then tends to level off, and may even rise slightly.
The optimal range is 12mm to 16mm: when the cavity thickness increases from 0 to the range of 12mm to 16mm, the K value of insulating glass will significantly decrease and its thermal insulation performance will sharply improve. This is because the enlarged air layer effectively reduces heat conduction and convection.
When the cavity thickness exceeds 16mm (especially 20mm), the convection within the air layer will start to intensify. A thicker air layer will form an internal circulation, which instead promotes the convective transfer of heat, resulting in a negligible improvement in insulation performance, or even a possible deterioration.
Economy and practicality: Excessive cavities will lead to an increase in the total thickness of the glass, impose higher requirements on door and window profiles, hardware and installation, and increase costs. However, the performance improvement obtained is very limited, and the cost performance is very low.
Other more important factors
Rather than blindly pursuing larger spacers, it is better to pay attention to the following points, which have a more significant impact on the final performance:
Filling gas: Replace dry air with inert gases such as argon (Ar) and krypton (Kr). These gas molecules are larger in mass and more inert, which can more effectively suppress convection and heat conduction, significantly reducing the K value by approximately 0.2-0.3 W/(m²·K). This is an upgrade option with extremely high cost performance.
Low-E glass (low-emissivity coated glass) : This is the most effective means to enhance the performance of insulating glass. The Low-E film layer is like a mirror, capable of reflecting far-infrared thermal radiation. In winter, it reflects the indoor heat back into the room, while in summer, it blocks the outdoor heat out. The role of a high-quality Low-E film is far greater than simply increasing the width of the spacer bar or filling it with inert gas.
Spacer bar material:
Traditional aluminum spacer bars: They have good thermal conductivity and can form "cold Bridges" at the edges of the glass, reducing overall performance and easily causing condensation at the edges.
Warm-edge spacer bars: Made of materials with low thermal conductivity such as stainless steel and composite materials, they can effectively cut off the cold bridge at the edge of the glass, increase the edge temperature, reduce the risk of condensation, and have better overall insulation performance.
The number of glass layers: For environments with extremely high requirements for sound insulation and heat preservation (such as in extremely cold regions and near airports), the three-pane two-cavity (two layers of spacer bars) structure is much more effective than simply increasing the thickness of the cavity of the double-pane glass.
