Condensation: A Physical Phenomenon, Not an Anomaly

First, let's understand why condensation occurs. Air contains water vapour. When the air temperature drops to a certain point, its capacity to hold water vapour reaches its maximum (saturation). If the temperature continues to fall, the excess water vapour condenses into liquid water, adhering to cooler surfaces. This specific temperature is called the dew point.Condensation forms on a glass surface when the glass temperature drops below the dew point of the surrounding air.. Based on this theory, if a vacuum glass window shows exterior condensation, it must be because the exterior glass surface temperature is lower than the outdoor air's dew point.

The Secret Behind Exterior Condensation on Vacuum Glass: A "Consequence" of Excellent Insulation

The core advantage of vacuum glass lies in its extremely low heat transfer coefficient (U-value). For example, the LandVac Titanium Vacuum Glass has a U-value as low as 0.4 W/(m²·K). This means it's exceptionally good at preventing heat transfer between the indoors and outdoors. So, what's with the exterior condensation? After rigorous investigation and analysis, the answer is precisely related to the excellent insulation performance of vacuum glass!

Consider the real-life scenario:

In a client's home, the indoor temperature remained stable at 25°C. In the early morning, as the sun rose, the outdoor air temperature rapidly increased from 0°C to 7°C. However, due to the incredibly effective thermal insulation of the LandVac vacuum glazing used by the client, internal heat transfer was extremely slow. As a result, the outdoor surface temperature of the glass didn't rise quickly enough with the ambient air, remaining at approximately 0.5°C.

The key points here are:

Outdoor air temperature was 7°C, with an assumed relative humidity of 80%, corresponding to a dew point of approximately 4°C.

The outdoor surface temperature of the vacuum glass was only 0.5°C.

Since the glass surface temperature (0.5°C) was less than the dew point temperature (4°C), the conditions for condensation were met!

Therefore, exterior condensation on vacuum glass is not a sign of poor performance. Instead, it's because its insulation is so effective that its outer surface is "slow to react" when the ambient air temperature rises rapidly. This causes its temperature to significantly lag behind the ambient air temperature, falling below the air's dew point. This phenomenon is also common with highly insulating materials (including vacuum glass, thick brick walls, etc.) under specific meteorological conditions (such as rapidly rising temperatures and high humidity in the early morning). As the sun continues to shine, the exterior surface temperature of the glass will eventually rise above the dew point, and the condensation will naturally disappear.

Conclusion: Exterior Condensation – A "Badge of Honour" for High-Quality Vacuum Glass

If the vacuum glass installed in your home occasionally shows exterior condensation under specific weather conditions (such as a clear early morning in early spring or late autumn), don't worry! This is not a product defect. On the contrary, it's a clear signal that the vacuum glass you are using has excellent thermal insulation performance! It effectively prevents indoor heat from escaping, which is why the outer surface remains at a lower temperature under certain conditions.

Choosing high-quality vacuum glass means opting for lower energy consumption, a more comfortable indoor environment, and more durable building maintenance. Its superior insulation performance will sometimes even demonstrate its capability to you through this "condensation" phenomenon.