I had new double pane windows installed and now dew is forming on the outside so I can't see through from early evening till early morning. There is a one inch border around the frame that doesn't dew up but the rest of the window builds up dew. My old dual panes didn't do this. My neighbors dual pane windows don't do it either discounting geography. The installer suggested I apply rain-x to the outside and that this is normal. I have not seen this behaviour in any one elses dual pane windows.