Analysis of Causes and Control Measures of Condensation in Insulating Glass

Internal condensation is a typical form of insulating glass sealing failure. What is the typical insulating glass condensation phenomenon? What is the dew point of insulating glass? What is the relationship between the dew point and temperature and relative humidity? How to test the dew point of insulating glass? What are the influencing factors and control measures of dew point?
1. Condensation inside the hollow glass
Internal condensation is a typical form of sealing failure of insulating glass. A survey shows that the failure rate of insulating glass after two years of use is 3% to 5%, of which 60% is condensation inside the insulating glass. The typical phenomenon is shown in the figure below.
Condensation will reduce the transparency of the glass and affect the thermal insulation effect. The accumulation of water vapor will also produce mildew. In severe cases, safety accidents such as the outer glass falling off will occur.


The internal condensation performance of insulating glass is characterized by the dew point, so what is the dew point of insulating glass?
2. What is the dew point of insulating glass?
The dew point refers to the temperature at which the humidity of the air sealed in the air layer reaches a saturated state, and is an important indicator reflecting the sealing performance of the insulating glass. When the surface temperature of the glass in the hollow layer is lower than the dew point of the air in the air layer, the water in the air will condense or frost on the inner 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.
So can we determine the air dew point by air temperature and relative humidity?
3. The relationship between dew point and temperature and relative humidity
The relationship between dew point and air temperature and relative humidity can be obtained in several ways: enthalpy-humidity diagram, table look-up method, formula method, etc.
A. Enthalpy wet diagram method. Determine the dew point temperature by querying the dry bulb temperature, relative humidity, isenthalpy, etc. in the enthalpy and humidity diagram. The typical enthalpy and humidity diagram is shown in the figure below.


B. Look-up table method. Calculate the dew point temperature at a certain temperature and relative humidity by querying the partial pressure of saturated water vapor at different temperatures. See the table below for the partial pressure of saturated water vapor at different temperatures under standard atmospheric pressure.