Understanding the foggy window issue
How to deal with a foggy window
Fogged up glass is a common sight in most houses with double pane windows. This phenomenon generally occurs during the winter months, when outside temperatures are way lower than the comfortably heated interior of a house. Despite being a regular winter feature, a misty window should not be taken lightly. Fogged up panes can be a telltale sign that your windows are in need of repair.
Let’s try and understand foggy windows a little better.
What causes a foggy window?
A foggy window is a direct result of condensation on the surface of the glass. The air around us contains water in its vapour state. This vapour consists of water molecules, spaced far apart. When temperatures drop, the air gets denser, and these water molecules are pushed closer to each other. This process continues till a critical temperature is reached, wherein the water molecules are packed close enough to resemble the liquid state. And condensation (or dew) occurs.
If your double pane window appears foggy, and doesn’t clear up on cleaning, it means that condensation has occurred on the inner faces of its panes. This automatically means that the seal around the glass panes of the window has failed, and a path has been cleared for moisture to enter the gap between the two panes.
Why is a foggy window a bad sign?
Since the sealant in a foggy window has failed, this implies that the gas originally filled in the gap between the panes has escaped. This in turn means that your double pane window is no longer insulating your home at full capacity. The air gap in a double pane window contains silica pellets. These pellets act as a desiccant, keeping the air gap dry. When a window starts fogging up, it also means that these silica pellets are saturated and will no longer absorb moisture.
If left unattended, a misty window will graduate to a ‘river-bedding’ situation, with water droplets cascading down the window, carving tracks on the glass surface. Another late-stage manifestation of a foggy window is the ‘silica haze’, a snowflake-like formation on the window pane, caused by the erosion of saturated silica pellets.
Is it possible to repair a misty window?
Often, the ‘fogginess’ in a window isn’t visible for months after the sealant failure. But once you do spot it, it is important to understand that it indicates a deeper underlying problem – that your home’s insulation is compromised. Some window repair services might offer to treat a misty window with a process commonly known as ‘defogging’. This essentially involves drilling a hole in the window and spraying a cleaning solution into its air gap. The solution is then vacuumed out and a defogger device is inserted into the hole, allowing any moisture entering the air gap to escape without fogging up the glass. While this process might remove visible ‘fogginess’ from your window, how it works is counter-productive to your home’s insulation. Here’s why.
To reduce heat transfer by convection, an insulating material contains air pockets within which air movement is minimised. A properly functioning double pane window reduces heat transfer by the small gap within which air movement is restricted. This trapped air (or gas) is a poor conductor of heat, and reduces heat transfer through the window. On the contrary, a large, ventilated space will actually encourage air movement and increase heat transfer, thus hampering insulation. Defogging relies on drilling a hole in the window’s glass, thus clearing a path for air to circulate freely. This dramatically reduces the window’s insulating capacity. Defogging is also ineffective in removing silica haze from a window. It is thus a cosmetic procedure, with a very low success rate. Replacing a misty window is a much more viable option in the long run. A new, well-insulated window will significantly lower your energy bills and pay for itself in next to no time.
Every window is unique, which is why it is best to rope in a professional window repair service to inspect your misty windows. A professional will be able to assess the degree of damage and provide you with the best possible foggy window repair or replacement solution.