Simply defined, window desiccant is absorbent material installed between the panes of multi-paned windows to absorb excess moisture and prevent condensation. However, when you look a little deeper, you will see that window desiccant is a little more complex than that, and the causes and cures for window condensation are as well. Read on to learn more.
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Essentially all air contains moisture in certain and fairly predictable amounts. When air is warm, the molecules of moisture are far apart and remain suspended in the air. When the air cools, they get closer together until they reach a temperature known as a dew point.
The dew point varies↗ depending on humidity, temperature, and pressure. For simplicity, when the air between the window panes contains enough moisture and reaches this dew point, condensation forms. So what does window desiccant have to do with it?
Window desiccant is a super absorbent material that removes moisture from the air. Generally, window desiccant has a lot of surface area and will last a long time before becoming saturated.
Double-paned windows go through a daily process of thermal exchange, flexing, and moving against the seal that keeps an inert gas inside to promote insulation and the elements outside. The window desiccant is designed to absorb any moisture that enters the air between the panes during this process.
There are a few different types of window desiccant made up of different materials. They all work a little differently and last varying lengths of time depending on what they are made of.
Silica gel or silicone insulation strips with a desiccant integrated into them are very common in double-paned windows.
Why is silica gel so common? Another part of the equation in windows is the desiccant compatibility with the insulating gases. The best desiccant to use depends on not only the gas used but the relative humidity and average climate of the geographic area where the window will be installed.
Ideally, a high-quality desiccant will have:
The better the desiccant, the longer the life of the window. But there can be other mitigating factors that degrade desiccant effectiveness and can cause it to fail.
Why would a desiccant strip fail? The short answer is this is caused when the moisture between the window panes exceeds the amount the desiccant can absorb. The cause is a bit more complex.
Windows flex and move with temperature changes, and eventually, even the best window seals will develop cracks, dry out, and then allow air, and therefore moisture to enter the space between the two window panes. The gas that helps insulate the window will often leak out when this happens as well.
When the desiccant becomes over-saturated, you will see condensation between the window panes. What this really means is that the window unit itself has failed and is no longer doing a good job of insulating your home.
There are only a couple of solutions for failed windows. You can take temporary measures, where a company will come out, attempt to reseal the windows, and then will re-inject the inert gas between the panes after using a device to “dry” the inside of the windowpane and remove moisture. This usually only works for a limited time because it requires drilling a small hole and resealing it after the gas is inserted. It won’t remove all the moisture from the desiccant, meaning this “repair” won’t last long before it becomes overwhelmed again.
The ideal solution is window unit replacement. You start with new seals, new desiccant, and the assurance that the window is again insulating your home effectively. There are some exceptions to this, and the best way to determine the right solution for you is to call a window or glass professional for a consultation.
The desiccant between your double pane windows is designed to help preserve the life of your window by removing moisture from the air. There are several types, and your window installer can help you choose what is right for you and your home. Once it stops working, you’ll need to determine why, and what your options are going forward.
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