Why does insulating glass condense?

December 21, 2022

As a glass product with mature material and production process, insulating glass has guaranteed product quality and is widely used in buildings. Due to problems in the management of individual insulating glass manufacturers, especially in the selection of materials, production process control and construction deficiencies, resulting in problems with the quality of their products, the most common is the condensation of insulating glass. In order to avoid such problems, this paper will make an analysis of the causes of insulating glass condensation.

1. Insulating glass dew point

The dew point of insulating glass is the temperature at which condensation occurs when the humidity of the gas in the spacer layer of insulating glass reaches saturation. That is, when the higher the water vapor content, the higher the glass dew point temperature. Dew condensation usually occurs when the temperature of the inner surface of the glass is lower than the dew point of the air in the spacer layer, and the water vapor in the air will condense on the inner surface of the glass.

2. The influence of edge sealing materials on the condensation of insulating glass

Side sealing materials are mainly butyl sealant of the inner channel sealant and silicone sealant of the outer channel sealant, polysulfide sealant, whose main role is to bond the various materials comprising the insulating glass, making it a whole, and has the role of preventing water vapor and other gases from entering the insulating glass spacer.

Butyl sealant is a single-component sealant based on polyisobutylene rubber, with a very low water vapor transmission rate and good adhesion, which together with the outer channel sealant constitutes an excellent moisture resistance system, which plays an important role in blocking the penetration of water vapor and other gases in the outside air into the insulating glass cavity. The role of the outer channel sealant is to bond the glass, spacer and other materials into a whole. To ensure the stability of the overall structure of the insulating glass, so it must have a strong bonding and mechanical properties. Avoid the structural displacement of insulating glass during use due to dynamic and static loads, thus ensuring the stability of the moisture-resistant system composed of inner channel sealant and outer channel sealant together. Therefore, the quality of the two sealants as the protective structure of the insulating glass determines the overall quality of the insulating glass and whether the phenomenon of condensation occurs.

3. The influence of spacing materials on the fogging and condensation of insulating glass

Spacer materials mainly include: aluminum spacer, stainless steel spacer, composite material spacer, etc. The spacer strip plays the role of bearing desiccant, matching sealing and overall structural strength. Whether the pore permeability of the spacer is excellent or not directly affects the play of desiccant's working ability, the standard of the spacer stipulates that the pore permeability of the spacer should meet: when the inlet air pressure is kept at 0.5 MPa, the air pressure difference value should be not less than 0.1 MPa, otherwise the desiccant in the spacer cannot play the role of water absorption normally. At the same time, the spacer should be straight, the side bow and waveform curvature is not more than 0.2%, distortion is not more than 0.5mm, no deformation, the corner to ensure the side flat, in order to protect the butyl rubber sealing width and sealing bonding effect.

4. The effect of desiccant on the condensation of insulating glass

The role of the desiccant is to absorb the water vapor in the insulating glass spacer layer, not only to absorb the initial water vapor when the production of insulating glass is completed, but also to adsorb the water vapor that continuously penetrates into the insulating glass spacer layer during the use of insulating glass, so that the gas in the spacer layer is kept dry to ensure that the dew point of insulating glass always meets the requirements during service.

5. the production process on the impact of insulating glass condensation

In the production of insulating glass, can affect the insulating glass condensation are mainly: the original glass cleaning, frame making, production environment temperature and humidity, filling desiccant, coating butyl sealant, closing the film, coating the second sealant and other process links.

  • The original glass sheet is not thoroughly cleaned, resulting in sweat stains, water stains and residual water beads adhering to the surface of the original glass sheet; the temperature and humidity control of the production environment is not strict and not dry enough; bending equipment during framing causes the back of the spacer to crack, and the surface of the spacer in contact with the butyl sealant is not smooth and has a bumpy phenomenon, etc., which can become a hidden problem that triggers the condensation of insulating glass.

  • The temperature and humidity control of the production environment does not meet the requirements, the interval between the filled desiccant and the combined piece is too long, the desiccant package is broken or the desiccant package is opened for too long, and the desiccant filling quantity is insufficient, which will also cause the insulating glass to condense.

  • Butyl sealant coating to ensure continuous and uniform, before coating should check the glass toughening flatness and spacing frame production quality, can not appear butyl adhesive coating discontinuous, broken glue and uneven, improve the bonding strength of butyl adhesive and glass and spacer, to avoid the resulting hollow glass condensation phenomenon.

  • Outer channel sealant coating depth is not enough, two-component sealant mixing effect is not good, does not meet the "insulating glass" national standard requirements: insulating glass outer channel sealant width should be ≥ 5 mm; insulating glass inner channel butyl sealant width should be ≥ 3 mm, will cause the insulating glass condensation.

Through the above analysis, it can be seen that there are many factors that trigger the condensation of insulating glass, in the actual production application, the cause of condensation of insulating glass may be a factor, but also may be a variety of factors superimposed. Therefore, when the problem of condensation occurs in the insulating glass, we must first clarify the mechanism of condensation in the insulating glass, combined with the environmental conditions in which the insulating glass is located, and then analyze the materials and processes that cause the problem one by one to determine the cause of condensation is a problem in which part of the insulating glass, and finally after a comprehensive analysis to confirm the specific causes of condensation, the corresponding production links to rectify the quality of the insulating glass to avoid the recurrence of condensation. problems.