Causes and solutions of condensation on the inner layer of insulated glass

11 2021

The original intention of insulated glass was to prevent condensation or frost on the window glass, which would affect the line of sight; for the entire building, the area of doors and windows accounted for more than 20% of the building area, and glass accounted for more than 70% of it. From a perspective, the energy consumption of heat dissipation through doors and windows accounts for more than 50% of the energy consumption of the entire building; then, improving the insulation and durability of insulating glass and avoiding its function failure are of great significance to the building energy saving industry.

In the insulated glass component, spacers, desiccant, sealant (or composite material) and glass form the edge sealing system of the hollow glass. The service life of insulated glass is directly related to the quality of the edge sealing system and the manufacturing process of the insulated glass, and is also affected by factors such as installation conditions and use environment.

But sometimes you will find condensation on insulating glass, so why does condensation appear on insulating glass? How to deal with the condensation of hollow glass?

The increase in the dew point of the hollow glass air layer is mainly due to the fact that water molecules in the outside air enter the air layer without being absorbed by the desiccant. There are many reasons for this result:

1. The glass is not cleaned thoroughly. With water vapor and water droplets, the adhesive force of the sealant to the glass will be greatly weakened, resulting in poor sealing effect of the insulating glass, leading to air leakage at the edge of the insulating glass, and increasing the possibility of external moisture entering.
Solution: Therefore, the glass must be carefully observed before combining the pieces to prevent liquid water from being present on the glass; therefore, the glass must be carefully observed before combining the pieces to prevent liquid water from being present on the glass.

2. The effective adsorption capacity of the desiccant is low. The requirement for desiccant is not only to absorb water vapor in the air of the insulating glass sealing layer, so that the insulating glass has a qualified initial dew point, but also to continuously absorb the water vapor diffused into the air through the adhesive layer to continue to maintain a dew point that meets the requirements of use. . If a low-quality desiccant is used as an adsorbent, its original water absorption capacity is relatively poor, and it will be saturated in a short time, and it cannot effectively adsorb the water molecules that diffuse into the air layer, which will cause the water molecules to gather in the air. , The dew point of insulating glass rises.
Solution: Choose 3A molecular sieve for traditional insulating glass that meets national standards as adsorbent.

3. Reasons for filling volume of desiccant. The standard for filling volume of hollow glass molecular sieve is not less than 70% of the length of the aluminum bar. Some manufacturers, in order to save costs or improper operation by the workers, the filling volume will be less than 70%. What's more, only 2 aluminum bars are filled. At the same time, the water vapor in the air layer of the insulating glass often exceeds the remaining adsorption capacity of the filled molecular sieve, which will greatly increase the possibility of condensation of the insulating glass.
Solution: The filling volume of molecular sieve must reach more than 70% of the length of the aluminum bar.

4. After the molecular sieve is filled, the reason for the length of time to combine the film. When insulating glass is made, cutting aluminum strips and filling molecular sieves are the first steps. After coating butyl glue and combining the sheets, there will be a time difference between them. At that time, the molecular sieve has absorbed a large amount of moisture in the air through the aluminum breathing holes, resulting in insufficient remaining adsorption capacity, thereby increasing the possibility of condensation of insulating glass.
Solution: Calculate from the molecular sieve unpacking, the molecular sieve filling-coating butyl glue-combining sheet-coating external sealant and other technological processes should be completed within 30 to 45 minutes; if the time is up, there is still no time to combine the sheets. The glue should be poured out of the molecular sieve in the aluminum strip, discarded, and refilled with the newly opened molecular sieve.