As part of the child safety requirements in the state's Building Code (2006 International Residency Code, Framing R613.2), the sill of any window (higher than 16-feet off the ground) needs to be at least 24-inches above the floor.
I recently experienced trouble getting an occupancy permit (I was renovating an old church) because the second floor windows are 22.75 inches off the floor and couldn't be moved due to post and beam structure. I had to put stops in all of the windows so they wouldn't open more than 4-inches and needed plexiglass in front of one window to meet the fire safety codes.
I can understand the requirement for new construction, but there should be some common sense applied when renovating historic structures and the importance of maintaining the integrity of the building design. I put this code right up there with the Home Sprinkler code... government is getting too darn invasive.
Where's common sense and personal responsibility?