Defogging double paned windows
I own a window defogging company. You can not drill into any type of safety glass. If you are carefull you can grind, not "drill" into the glass, but it will eventually break, might be a week from now, but it will break. When it does break it explodes, into a million tiny pieces. Drilling into the spacer bar does not let the unit vent enough. Plus sealed units are fairly inexpensive. If you are willing to take it all apart, just replace it. Several defogging companies will sell you valves. I have given them to people wanting to try it them selves!