Foggy, cloudy windows are no one’s idea of a good look. This condition occurs naturally when warm, moist air condenses on a cold surface, but it’s not supposed to happen inside your windows. But you don’t have to live with cloudy windows forever. This guide will explain why window fogging happens, and how you can repair fogged windows in your home. This repair can be done at home and cheaper compared to many window repair costs.
Why Do Windows Fog Up?
Windows fog up when the temperature of the air outside is considerably lower than the temperature of the air indoors. As the cold air cools the windowpane, the warm, moist air inside condenses on the pane, causing fogging and calcium deposits to appear. This is a natural process, but it’s not supposed to happen in your windows.
First, it’s important to note whether the fog is on the exterior of the glass (inside the home or outside the home) or between the panes. If you’re able to wipe the fog away, this is simply humidity condensing on the cooler glass. Wiping the surface with a glass cleaner will usually solve this issue for a while. However, there’s more to the solution if the fog is between the panes.
Modern energy-efficient windows consist of insulated glass units (IGUs). These units are made up of two or three panes of glass sandwiched together with an airtight seal around their perimeters. In between the glass panes, there is a gas, whether it be air, argon, or krypton. The job of the gas is to remain invisible while also preventing the transfer of thermal energy. Air provides adequate insulation, but since argon and krypton are inert gasses and are heavier, with slower-moving particles, they are more effective and energy efficient.
In an ideal world, the IGU would prevent the warm, moist air that’s inside a home from ever reaching the most exterior pane that’s cooler than the other pane(s). The interior pane and inert gas should prevent the transfer. However, when the seal around the panes starts to deteriorate, gas will escape, and warm air can work its way in between the panes. If that exterior pane is cool, moisture will now develop.
The seals will deteriorate over time, as will the inert gas between the panes. When this happens, not only does cloudiness occur, but the window’s energy efficiency will also begin to break down.
How to Repair Fogged Windows
There are a few routes that homeowners can go to fix their fogged windows. Below includes a few options, including whether you’d like to attempt handling the project yourself or prefer to call a professional.
1. Replace the Window Sashes
The easiest way to repair a fogged window is to replace the window sash itself. The sash is the IGU and the frame around it. Most windows have two sashes and replacing them will provide the homeowner with a brand-new, intact IGU that prevents fogging. The old sash pops out, and the new one drops in.
To replace a sash, homeowners must take perfect measurements of their existing window sash and contact the manufacturer. If the manufacturer does indeed offer replacement sashes, the homeowner can order one and have it delivered. This can be expensive but ordering multiple sashes may help the homeowner save money on a per-window rate.
How to Accurately Measure for a New Window Sash:
- Unlock the window and slide the bottom sash up a few inches.
- There are two window latches on the top of the sash. Pull these latches inward simultaneously to release the sash and tip it into the room.
- Once the window is horizontal, lift one corner out of the window track and remove the sash.
- Using a tape measure, measure the width of the window first. You’ll want to measure the width at three spots to ensure you calculate precisely: across the top, the bottom, and the middle of the sash, and then record each measurement. Circle the smallest number and mark it with a “W.”
- Next, measure the height of the sash at the left, middle, and right. Record each measurement, choose the smallest, circle it, and label it with an “H.”
- Call the manufacturer and provide them with the circled measurements in the form of “W by H.” This ensures that the sash will be in the proper orientation.
When the new sash arrives, reverse steps 1 through 3 to replace the window and latch it into place.
2. Replace the Windows
Another option for getting rid of the fog in older windows is to completely replace the windows themselves. Replacement windows will be all-around more energy efficient, and there may even be rebates available when upgrading from older, less efficient windows.
When it comes to replacement windows, it’s customary for a company come to your home, measure each window, order replacements, and install them for you. To do so, they remove the existing panes and window stops, secure the replacements in place, and caulk, seal, and trim around them. The exterior of the home (and the existing window frame) would not need to be disturbed. The downside is that this method is expensive, but experienced DIYers have the option to save money by ordering and installing their windows themselves.
3. Replace the IGUs
Another alternative is to swap the old IGU for a new one. Doing this will restore the window’s energy efficiency while retaining the old sash frame. It’s important to note, though, that this is a more involved job than replacing the sash, and it’s often best for a professional window company to handle this than for a DIYer to do it on their own—but it can even be hard to find a shop willing to do it.
As an overview, replacing an IGU involves removing any retaining clips or strips holding the glass into the sash and cutting through the old sealant to remove the IGU. The shop will measure the IGU and either build its own or order a replacement. Then, the shop will use special sealants to seal the new IGU in place, ensuring that the seal is air- and water-tight, and reinstall the strips or clips. There are many other nuances involved with the project, and these tricky details can be difficult for DIYers.
3. De-fog the Windows
The final option for repairing fogged windows is called defogging. This method does nothing for the energy-efficiency loss but will ultimately bring a window back to its former transparent glory.
Defogging involves drilling holes in the glass, injecting cleaning solution into the space between glass panes, removing the soiled liquid, and then injecting a drying solution between the panes. Once the interior of the glass is completely dry, the holes are then sealed and the window is good to go and completely free of fog.
The issue with defogging is that, as mentioned, it doesn’t restore any lost energy efficiency from deteriorated window seals. However, it most likely won’t hurt energy efficiency either, considering leaky seals cause fog and condensation. Also, DIYers without experience working with glass may be more likely to break or chip the glass while drilling, meaning they’ll have to order a new sash or IGU anyway.
Replacement is the Best Option for Fogged Windows
Whether the plan is to replace the sash, just the IGU, or the entire window, replacement is the smartest avenue when it comes to repairing fogged windows. Doing any of these things will do away with foggy glass and also restore energy efficiency. Homeowners will benefit from new, clean, fog-free windows, improved comfort, and reduced energy consumption.
