Analysis on causes and how to control of condensation in insulating glass（IGU）

Internal condensation is a typical form of insulating glass seal failure. What is the typical phenomenon of insulating glass condensation, what is the dew point of insulating glass, what is the relationship between dew point and temperature and relative humidity,and what are the influencing factors and control measures of the dew point of insulating glass? 

1. Dew condensation inside IGU glass

 Internal condensation is a typical form of insulating glass seal failure. An investigation shows that the failure rate of insulating glass is 3%-5% after two years of use, of which 60% is condensation inside the insulating glass. The typical phenomenon is shown in the following figure.

Condensation will reduce the transparency of the glass, affect the heat preservation and insulation effect, moisture aggregation will also produce mildew, serious when the outside glass off the safety accident.

Dew point is used to characterize the dew point of insulating glass. What is the dew point of insulating glass? 

2. What is the dew point of insulating glass? 

Dew point refers to the temperature when the air humidity in the air layer reaches saturation, which is an important index reflecting the sealing performance of insulating glass. When the surface temperature of the glass inside the hollow layer is lower than the dew point of the air inside the air layer, the water in the air will form dew or frost on the inside surface of the glass.

There is a one-to-one correspondence between dew point and air temperature and relative humidity. The higher the relative humidity, the higher the dew point temperature. Conversely, the lower the relative humidity, the lower the dew point temperature.

3. Influencing factors and countermeasures of dew point of insulating glass

The dew point of insulating glass is mainly affected by the following factors:

1). Relative humidity of the production environment. The relative humidity of production environment mainly affects the effective adsorption capacity and residual adsorption capacity of desiccant. When the relative humidity of the middle glass composite space is large, on the one hand, the water vapor in the air layer of the insulating glass is large, on the other hand, the residual adsorption capacity of the desiccant will be reduced, especially when the desiccant is exposed to the air for too long.

2). Desiccant filling quantity and quality. Some manual filling desiccant process can not ensure a stable filling amount, resulting in desiccant adsorption capacity is insufficient; Certain inferior desiccant cannot adsorb water molecule effectively, or reacts with water molecule to appear spacer corrosion phenomenon.

3). Edge sealing quality. The water vapor seal of most insulating glass relies on butyl rubber. The quality of some butyl rubber is difficult to guarantee when it is manually applied, which will lead to seal failure. Part of the two sealant doped with white oil, dissolved butyl glue caused by the flow of oil and water vapor leakage; Low-E glass edge is not removed or treated thoroughly, the edge sealing adhesive is not reliable, water vapor invasion leads to film oxidation, etc.

It can be concluded that strictly controlling the relative humidity and exposure time of desiccant in the air during the production of insulating glass, selecting high-quality desiccant and stable and reliable filling process, ensuring the quality of butyl rubber and second sealant materials and gluing, and carrying out timely and effective quality inspection are the keys to controlling the dew point of insulating glass.

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