Glass, an effective counter measure to IR guided munitions?

Watching Myth-busters on tv they demonstrated that IR or Infra Red cannot pass through glass.
The heat signature of a person standing behind a common all garden pane of glass is totally hidden from an IR camera,
because IR cannot pass through glass.

So can IR munitions target through glass? Or to put it another way can you target a tank inside a glass hut (assuming for the moment we pretend we cannot visually see the tank)?