How To Repair Foggy Window Glass

The Cause Of Window Failure & Glass Fogging

Double glazed windows commonly known as dual pane windows, have almost entirely replaced single pane windows in new home construction. The sealed dual layer glass panes are filled with a special gas that increases noise reduction, improves thermal performance and maintains the clarity of the glass. Unfortunately in most all cases the seal surrounding the outer layer of the dual panes fails over time. As a result, moist outside air gradually replaces the gas between the glass, causing window fogging and condensation to appear. The fogging may come and go with temperature and weather change, but clarity generally only worsens over time. Studies show average dual pane windows loses about 1 percent of their argon gas each year. Significant window fogging commonly starts to appear within 10-20 years of installation, or sooner depending on the quality of the windows.

Solutions To Fixing Foggy Windows Glass

If you are lucky enough to have your windows still under the manufactures warranty when fogging starts to occur, you can likely have the glass replaced at no cost. This should be your first step is finding out if your windows are still under warranty.

If the warranty has expired some options are:

  1. Live with the foggy glass with decreased clarity over time.
  2. Have a glass company replace the entire window if needed.
  3. Replace just a single glass pane without replacing the entire window. 
  4. Lastly with some basic tools you can attempt defogging the window glass yourself.

Window replacement costs can be quite high, with the costs varying depending on the window type and size.

The average costs to fix a foggy dual pane window:

  1. Full window replacement – $500-$2000
  2. Single dual pane glass replacement – $300-$1000
  3. DIY window defogging with and without some basic tools – $0 – $100 

*Failed dual pane windows lose some of their thermal performance over time. Don’t worry though. The resulting increase in energy costs due to failed window seals rarely ever comes close to or surpasses the cost of a full window replacement, even over many years.

Consider Defogging Your Windows Before Replacing

If you’d prefer not to spend a lot of money on window replacement try this simple tip which may be able to defog your windows or improve their clarity. A good final solution to try before opting to have the window glass replaced.

*Please note! -This DIY solution will not work with tempered glass. Tempered glass cannot be drilled without shattering. It is safety glass. Most all glass doors including sliding glass doors, very large windows, as well as bathroom, and entry way windows such as side lights are tempered! Usually you can look for an etching in the corner of the glass that will say “tempered”.

In some cases this method works very well and restores window clarity 100%. It also may restore only partial clarity or none at all if the windows are heavily stained or have been foggy for some time. 

The Shortcut - How To Defog Your Windows In 3 Simple Steps

1. Gather the tool you'll need for this window glass defogging project

Tools Needed

  1. A good cordless drill.
  2. 6mm, 8mm, or 10mm diamond drill bit for easy glass drilling. 
  3. Hand vacuum for cleanup.
  4. Heavy duty clear tape to cover the small drill holes after defogging.
  5. Small pin or needle to puncture vent holes in the tape for air circulation.
  6. Spray bottle of water to cool the drill head while cutting glass.

If you don’t already have one. A good cordless drill is very useful for this and many other household projects. This 20v Black & Decker Variable Speed Drill is a highly rated affordable cordless drill that will handle most any project. A long life lithium Ion battery holds its charge.

These quality carbon steel diamond plated drill bits are perfect for this precision glass cutting project. Also useful for drilling porclain, ceramic, tile, and marble. The 10 piece set has varying sizes from 6mm to 50mm for most any project. Fits most standard drills.

2. Drilling

Be sure you are drilling on the INNER LAYER (inside your home) of the dual pane glass. Use a smaller drill bit for smaller window panes, and larger for larger glass. Start your hole in the top left corner about 1/2 inch in from the corner of the window. First lightly wet the glass, and begin drilling carefully into the layer of glass. Drill slowly and keep the drill head wet with your sprayer. Keep pressure light to be sure to not drill too far and hit the outer layer of glass. Do the exact same in the bottom right corner of the window glass. This can be done in reverse corners of the window, for example if you wanted the hole to be behind a drape. The important thing is the holes are diagonal from each other.

3. Final Steps

Using your hand vacuum, clean up any loose glass particles from drilling. You can also use the vacuum at one of the drill holes to help speed airflow between the glass to clear the condensation quicker. It may take up to 24-48 hrs to see any significant improvement in the clarity of your window. After the window has cleared, cut and place a small 1 inch square of heavy duty clear tape over the drill hole to keep bugs and dirty from entering between the panes of glass. Using a needle or pin poke several small holes into the tape so the window will continue to vent. That’s it!