When Double Glazed Windows Are Misting Up With Condensation If you have double-glazed windows that are leaking with condensation, then this is an indication that the seals between the glass panes have failed. However, repairing these windows isn't as difficult as you think, and it is possible to do it http://www.stes.tyc.edu.tw/xoops/modules/profile/userinfo.php?uid=1214777