What Causes Foggy Windows?

What Causes Foggy Windows?

Double (and triple) pane glass windows are energy efficient but can become foggy windows over time. The rubber seal surrounding the two layers of glass can loosen, allowing moisture to seep through and become trapped between the layers. Even just a pinhole break can create foggy windows. Windows, by design, are all destined to fail much the same way light bulbs are expected to burn out eventually. Thermal pane windows are made with eventual failure in mind due to the natural occurrence of a phenomenon called solar pumping.

What is Solar Pumping?

Solar pumping naturally occurs on a daily basis when sunlight heats and pressurizes the inner airspace of the window cavity during the day. This forces small amounts of air out of the window cavity through the semi-permeable seal. When the temperature drops at night, the window cools and lowers pressure in the window cavity which draws air back inside. Over time this daily ‘breathing’ process allows moisture into the window cavity which gets absorbs by the windows Silica desiccant material (moisture absorbing material installed during window manufacturing to prevent fogging). After the desiccant material becomes saturated, the excess moisture has nowhere to go except on the surface of the glass. Another foggy window is born! In a large majority of the clients we work with, the foggy window situation is the result of the window coming to its intended useful life span. We typically restore windows that are 10 to 12 years in age, depending on the quality and intended life span of the moisture absorbing desiccant material inside the window cavity. Other variables like climate, air humidity and window position in relation to the sun also affect the likelihood of foggy windows.

The Risks of Prolonged Foggy Windows: If moisture is allowed to continue collecting through the process of solar pumping, there are a few risks you should be aware of. Eventually the windows become permanently foggy, leaving deposits, strains and mold. Unfortunately, we won’t be able to restore the window after it gets to this point.

Leave a Comment

Your email address will not be published. Required fields are marked *