Time to start looking at the new changes coming from the upcoming ICC codes for buildings in 2012!
Sill height is a requirement that will affect almost any 2 story building and thought I would do a quick post on it. Basically these rules serve the same purpose that railings serve for stairs. If your floor is high enough above the ground below then a higher sill will keep small children from falling out of the window.
The 2012 IBC and 2012 IRC require the bottom of openings created by operable windows to be a minimum height above the adjacent interior floor when they are 72 inches or more above the grade outside the window. In the 2012 IBC the required height of that window sill above the adjacent interior floor is 36 inches. In the 2012 IRC the required height is 24 inches.
Both codes include an exception for windows that do not open more than 4 inches or that are equipped with window guards or opening controls that comply with ASTM. The WOCD must limit the initial opening of the window to no more than 4 inches, but must also be releasable with no more than 15 pounds force to open more fully. The intent of this later provision is to permit windows that are equipped with window opening control devices to also be used to meet the Emergency Escape and Rescue Opening requirements of the 2012 IBC and 2012 IRC.