Double-Pane Glass are two panes of glass separated by a sealed space filled with air or insulating gas (like argon gas), creating a thermal barrier that significantly improves energy efficency, reduces noise and prevents condensation compared to single-pane glass by slowing heat transfer and blocking sound. These units are crucial in modern windows, enhancing comfort and lowering energy bills in home and buildings.
Unfortunately, not all IGU’s are everlasting, for one reason or another you may end up having an accident and end up breaking your double-pane glass and even though only one side of the glass is broken both the inside and outside panes will be replaced upon repairs, since a double-pane glass comes sealed together as a unit.
You may also not even have a broken unit but you could encounter a damaged seal inside your IGU. Some companies will try to convince you that you need a full new window replacement when you have a broken or damaged unit and this is not always the case. It’s almost ways possible to just replace the glass in your window/door, and this will always be the cheaper option.
Some signs of seal failure in double pane glass are,
Fogginess
You may notice some of your windows may be more clearer than others or that some have a thick hazy white coating not letting enjoy the view of your backyard.
Condensation
In some cases when the seal breaks in-between the unit, humidity can slip into the unit and you can visibly see water drops or sweat in-between the 2 layers of glass. If the spacer of your IGU is made of metal you may also notice rust building up do to the humidity that is inside the glass.
Loosening Of Seals
Another noticeable way is when you have windows with muntin bars. Due to the humidity and all the changes in temperature that can now enter your unit, all this will affect the structure of your glass and may occasionally cause the bars to fall from their position.
The swivels or spacer in-between the unit can also start to fold inwards and become visible and unappealing.
LowE Deterioration
Almost every Double Pane Glass has a LowE coating tint on the outside pane, this is one of its key factors in it’s energy-efficiency. Over time you may start to notice colorful rainbow like marks or spots on the outside pane which is an indication that the glass has lost its seal.
J & J's Glass And Window Repairs 