Fog Between Glass

Double pane windows are built with two panes of glass that are sealed together with a narrow space separating them (usually around one-half inch wide). Most double pane windows perform ideally for many years. However, these sealed window units can develop fogging issues inside, which can cause them to look very dirty and can seriously reduce the visibility through the glass. Leaking seals occur in many double pane windows after many years of use.

Topics covered in this post:

  • How Double Pane Windows Work
  • What Causes Window Seals to Break?
  • When do Window Seals break Between Double Panes?
  • Cleaning Between Panels of Double Pane Windows
  • Avoid Altering Windows in Attempts to Clean
  • Solution to Condensation Between Window Panels
  • High-Quality Energy-Efficient Double-Pane Windows

Double pane windows are in very wide use today, so here’s are some helpful tips if you notice window condensation between panes in your home.

How Double Pane Windows Work

The two panes of glass in a double-pane window create insulative dead airspace between them. This design reduces heat transfer, which helps maintain interior temperatures against heat loss. Today’s state-of-the-art double pane gas filled vinyl windows typically feature twoseals — an inner seal to block and prevent corrosion, and an outer seal to strengthen the structure of the window. The seals also keep the spacer in position, which is a tube containing a desiccant, which is a mix of chemicals that absorb moisture.

What Causes Window Seals to Break?

Overall, double pane windows work exceptionally well. They are built to withstand extreme weather conditions, from very hot to very cold temperatures, high humidity, and more, all while being opened and closed frequently every day. The double seal used in the construction of modern double-pane energy-efficient windows provides protection even if one seal breaks. The other seal continues to hold the sealed window together at least for some additional period of use. But, of course, over time all windows age, and parts eventually do break down. The normal life expectancy of double pane windows is between approximately 10 and 20 years. Window seal failure causes include weakening and degrading from environmental stresses, such as:

  • Wearing of the seal due to aging
  • Poor water drainage around the window
  • Extreme buildup of dirt, dust, and grime hardened along the seals
  • Long-term direct sun exposure in hot climate
  • Heat buildup in extreme climates
  • Untempered long-term exposure to extreme weather
  • Frequent expansion and contraction during freeze and thaw

When do Window Seals break Between Double Panes?

After the seal is broken, moisture can collect between the window panes. Moisture between window panes can cause windows to lose basic functionality. These are the primary reasons to have double pane windows repaired:

  • Energy efficiency: Broken seals cause loss of energy efficiency and cost savings.
  • Visibility: Breached seals allow condensation and fogging between panes.
  • Appearance: Moisture between panes can make windows look very dirty.

Trying to Clean Between Panels of Double Pane Windows

When the seal fails between window panes, moisture can make its way into the space between the glass panels. Moisture between the panels can cause the windows to fog over and look very dirty and reduce or entirely block visibility through the windows. But, cleaning between the glass panels of double pane windows presents serious safety and efficiency problems. It also creates an irreparable breach in the sealed double glass window unit.

To the question of how to get rid of condensation in between the double panes, the short answer is that you will probably need to have professional repair or replacement of leaking double pane windows. Consider the problems with the alternative of attempting to clean between sealed glass panes: It would involve breaking apart the seals from around each of the glass panes. After cleaning each panel of glass, you would be challenged with reassembling the panes to configure a double pane unit and reseal them on both sides to make a well-sealed double pane window.

To clean between the glass panes means you would need to take the panes apart, which would break the seal entirely. Then resealing the window panes together somehow without moisture between them is too unlikely to work to create a well-sealed window. The point here is that, ultimately, it is not possible to clean between the two panels of double pane windows without destroying the functional value of the window. The reassembled window unit can be expected soon to exhibit the same signs of seal leakage that led you to your difficult cleaning effort, requiring you to repeat the laborious process frequently.

Avoid Altering Windows in Attempts to Clean

Here is a note of caution about potentially questionable recommendations you may find online for cleaning double pane windows to remove condensation between panels. For example, there is questionable advice about drilling a hole at the top of the window large enough to push a cloth attached to a wire through to clean between the double panes.

This may seem like a quick and free solution, but drilling a hole large enough to fit an adequate cloth wrapped around a wire at worst risks breaking the glass panes and even injuring someone. At best, it eliminates the usefulness of the seal between window panes, creating easy access for moisture, dust, and debris through the new hole. Even if you plug the hole you’ve drilled and diligently monitor the condition of the plug, the plug is likely to be insufficient to maintain the seal under ongoing use of the window.

Solution to Condensation Between Window Panels

Manufacturers design and build double pane windows to remain sealed together. They are not designed to be disassembled for cleaning and then reassembled. The practical approach to the problem of seal failure in double-paned windows resulting in the dirty appearance of the glass is to consult your window installer or manufacturer for an appropriate solution. For newer windows, expect a recommendation to have a warrantied repair or replacement. For older windows, expect double pane window replacement to be suggested as your most practical option.

Double pane windows are in very wide use today, so here’s are some helpful tips if you notice window condensation between panes in your home.