We are seeing polycarbonate sheet used in windows of residential structures in high crime or affluent neighborhoods. The best way here to create ventilation is to take the window frame out. You can use a variety of tools including a sledge hammer. A good quick drill is to show firefighters the material, play with it and build/destruct some window assemblies. However, polycarbonate is not cheap. If you check with some local suppliers, they may have small drop pieces that they would be willing to donate.