Inevitably the seal in between two panes of glass gets old and breaks down. Gases are then usually released and/or react with the air giving it a wet, foggy, and/or discolored look. The only remedy is replacement. Often there is usually at least one window at most homes that has a broken seal or vapor barrier. The more sun at your home the more likely you are to have issues with this problem. Drastic temperature changes also play a factor, and here in Utah we are certain to experience that. Please understand this is not a reflection on the home or the homeowner – it happens everywhere.