Your double pane windows make a huge difference in the insulation in your home. They are made to keep the outside temperature from affecting the inside temperature. Sometimes though, you will find that your double pane windows turn foggy or look like they have condensation inside them. This is usually caused by a failed seal, which keeps the insulating gas inside your window. When that seal fails, your window will all of a sudden stop working as an insulator.
The reason for this failure is the way the gas reacts when exposed to sunlight. It will heat up and expand, only to contract again when it cools down. Over time, this repeated motion can cause the seals made from silica gel to fail, allowing outside air to infiltrate the window, leading to moisture being trapped between the panes.
Unfortunately, there is no way to get your windows back to the way they were. There is a process for replacing the gas inside and re-seal the windows, but the window won’t be back to its original efficiency.