What are my options when it comes to window glass?

A quality window unit has two or three panes of glass in the frame, separated by thin spaces that are filled with inert gas (usually argon) and sealed. These insulating glass units greatly decrease the amount of heat loss through the window, as well as limiting condensation or frosting. In most cases, triple panes (tri-pane) windows have somewhat better insulation performance than dual-pane units. Quality window glass is also treated with a low-emissivity (Low E) coating of microscopically thin metal such as silver. The Low E coating blocks UV radiation and radiant heat transfer.
In regions prone to hurricanes, codes require that windows be fitted with impact glass that resists breakage and does not shatter like standard glass if it does break. A hybrid of tempered glass and laminated glass, impact glass is also required in areas where someone could fall into the glass, such as floor-level windows and windows in stairways.