Insulated Glass Unit (IGU) vs. Vacuum Insulated Glass (VIG)
In the construction industry, Insulated Glass Units (IGUs) have become one of the most popular choices for modern buildings. However, a common misconception is that IGUs are the same as Vacuum Insulated Glass (VIG).
In reality, the two systems have completely different structures and working principles. Understanding these differences is essential to selecting the right glazing solution for your project.
1. Structure and Principle of Insulated Glass Unit (IGU)
An IGU consists of two or more glass panes separated by a spacer bar and hermetically sealed with specialized sealants.
The cavity between the panes is not vacuum, but filled with dry air or inert gases such as Argon or Krypton.
Spacer bar: Usually made of aluminum or low-conductivity “warm edge” materials. It contains perforations filled with desiccant beads that absorb residual moisture, preventing fogging and condensation inside the cavity.
Sealing system: An IGU typically uses a dual-seal structure:
Primary seal – Butyl: Applied around the spacer to provide a moisture barrier and minimize gas leakage.
Secondary seal – Two-part Silicone: Provides structural integrity, adhesion, and long-term durability of the IGU.
Figure 1: Simulation of multi-layer insulated glass
2. Structure and Principle of Vacuum Insulated Glass (VIG)
Unlike IGU, VIG is a high-performance glazing technology. It consists of two glass panes separated by an ultra-thin gap (≈0.2 mm) in which the air is almost completely evacuated to create a vacuum layer.
Micro-spacers: Tiny, almost invisible support pillars evenly distributed between the panes prevent the glass from collapsing under atmospheric pressure.
Thermal insulation principle: By eliminating almost all heat transfer through conduction and convection, VIG achieves superior thermal performance compared to conventional IGUs.
Performance: With its vacuum gap and micro-spacer design, VIG can achieve thermal insulation equivalent to much thicker IGUs.
3. Thermal Performance (U-value)
The U-value is the most important indicator of thermal insulation performance. The lower the U-value, the better the insulation.
Single glazing: ≈ 5.8 W/m²K
Standard IGU (double glazing with Argon): ≈ 2.5 – 2.8 W/m²K
High-performance IGU (with Low-E coating): ≈ 1.4 – 1.6 W/m²K
VIG: Comparable or even superior to high-end IGUs, with significantly thinner construction.
Figure 2: Taniglass QC staff inspecting finished insulated glass units
4. Acoustic Performance – Is IGU the best choice?
Although IGUs provide moderate sound insulation, their primary strength is thermal insulation.
The acoustic performance of an IGU depends largely on the glass thickness and the cavity width.
For superior soundproofing, laminated glass or IGUs combined with laminated glass are more effective solutions.
👉 If you require further technical consultation on specialized glass products or want to select the most suitable glazing solution for your project, feel free to contact us for professional support.
