Condensation is a natural process that occurs when water vapor in the air turns into liquid on a surface. In buildings, this process can occur on windows and glazing, particularly in insulating glass units (I.G.Us). However, condensation on the surface of an I.G.U is not normal and can indicate that the unit is not functioning properly as a thermal barrier between the inside and outside of a building.
The purpose of an I.G.U is to keep heat inside a building while preventing heat from escaping through the glass during cold weather. When the inside surface of the glass is warmer than the outside surface, the I.G.U is functioning properly. However, if the outside surface of the glass becomes colder than the dew point temperature of the surrounding air, condensation will form on the inside surface of the glass.
There are several factors that can impact the temperature differential between the inside and outside surfaces of an I.G.U. One such factor is the use of a low-e coating. Low-e coatings reflect interior warmth back into the building, which can increase the temperature differential between the inside and outside surfaces of the glass. Additionally, the type of glass used in the I.G.U can impact the temperature differential. Clear, low-iron, or lightly tinted glasses tend to have a higher infrared transmittance and can create a greater temperature differential during the day.
When condensation occurs on the surface of an I.G.U, it can be an indication that the unit is not functioning properly as a thermal barrier. There are several solutions to address this issue, including adding more insulation to the surrounding building materials, increasing ventilation, or replacing the I.G.U with a higher quality unit that is better suited to the climate conditions of the building.
In conclusion, condensation on the surface of an I.G.U is not normal and can be an indication that the unit is not functioning properly. Understanding the causes of condensation, including factors such as low-e coatings and the type of glass used, can help to identify potential solutions and prevent further damage to the building. By addressing this issue promptly, building owners and managers can help to improve the energy efficiency and overall performance of their building.