The width of the commonly used spacer bars in insulating glass usually directly determines the thickness of the air layer in insulating glass. This width is a key parameter that affects the thermal insulation, heat insulation and sound insulation performance of insulating glass.
Mainstream width specifications (unit: millimeters)
9mm / 9A - This is the most economical and common specification, widely used in ordinary residential doors and Windows where performance requirements are not high. It can meet the basic requirements for thermal insulation and heat preservation.
12mm / 12A - Currently the mainstream and preferred specification for home decoration doors and Windows. It achieves a good balance in terms of heat preservation, heat insulation and sound insulation performance, and has a high cost performance. Here, "A" is the abbreviation of "Air", representing the thickness of the air layer.
15mm / 15A - A better performance specification. The thermal insulation effect is superior to 12A, especially when combined with Low-E glass, it can form a better "warm edge" effect.
18mm / 18A, 20mm / 20A - these are high-performance specifications. It is usually used in situations with higher requirements for sound insulation and heat preservation, such as in extremely cold regions, residences facing the street with high noise levels, and high-end system doors and Windows, etc.
Wider spacer bars such as 27mm and 36mm - these are typically used in triple-pane double-chamber insulating glass filled with special gases (such as argon) to achieve extremely high energy-saving standards.
How to choose the appropriate width?
When choosing the width of the spacer bar, it is not the case that the wider the better. A comprehensive consideration is needed:
Thermal insulation performance (K value /U value) :
Within a certain width range (usually 12mm-18mm), the thicker the air layer, the weaker the convective and conductive heat transfer will be, and the better the insulation performance will be.
However, when the air layer is too thick (for example, over 20mm), air convection will occur within the cavity, which will instead reduce the insulation effect. Therefore, there exists an optimal performance range, typically between 12mm and 18mm.
Sound insulation performance
Insulating glass has a good isolation effect on medium and high-frequency noises (such as voices and car horns), but its effect on low-frequency noises (such as car engines and road tire noise) is slightly worse.
The sound insulation performance does not increase linearly with the thickening of the air layer. Using asymmetrical glass thicknesses (such as 5mm+20A+8mm) or combining laminated glass and insulating glass often has a more significant effect on enhancing sound insulation than simply increasing the thickness of the air layer.
Cost
The wider the spacer bars are, the more materials are used, and the total thickness of the glass increases, which will lead to a corresponding rise in the costs of profiles, hardware, installation, etc.
Summary and Suggestions
For ordinary household use and cost-effectiveness: The 12A is currently the most balanced and recommended choice.
For better thermal insulation and heat preservation effects: 15A or 18A can be chosen, and it is recommended to use Low-E glass in combination.
There are special requirements for sound insulation: Do not just focus on the width of the spacer bars. A more effective solution is to choose a combination of "laminated glass + insulating glass" (for example: 5mm laminated +12A+5mm), which has a significant effect on isolating medium and low-frequency noise.
In extreme climate regions or passive houses: A three-glass two-chamber structure should be considered. Its spacer bars are usually wider (such as 27mm) and filled with inert gas.
