Insulated Glass Units deflecting

 Thermal Pane or Double Glazed or Dual Pane or Insulated Glass Units will all fail over time. Barometric changes and fluctuations in temperature create pressure differentials between the inside air space and the atmosphere. These pressure differentials cause the lites of glass to deflect inboard or outboard which in turn creates, over time, a weakness in the glass sealant interface. Eventually ambient air with is residual water vapour will be drawn into the sealed united during its cooling cycle. 

Why thermal pane windows fail and cause condensation

Drilling window glass to remove moisture and fog ... what is the best tool

Inexpensive battery operated rotary tools provide the best results for drilling through clear glass lites of glass. Rotary tools from Dremel, owned by Bosch, Black and Decker, Sears Craftsmen all produce the same results. Use a 4mm diamond burr or drum bit, run the rotary tool at near maximum rpm and with a steady hand begin to carve a cresent shaped groove to steady the dremel as you drill through the glass. Note; YOU CANNOT DRILL TEMPERED GLASS WITH THIS METHOD