According to the local city code and the IMC, intake and exhaust vents for buildings are to be 10 foot minimum above grade. I see intakes and exhaust louvers below this height all the time, i.e just above doors. I have an old historic building which there is no way to get the intake and exhaust louvers for the main airhandler to the 10 foot height without installing ugly looking ducts running up the side of the building to get to the 10 foot mark. The AHU is in the basement with 6 inch think concrete floor above it and a sloped slate roof. The only option would be to install the louvers under the 10 ft mark in the sidewall of the building, or run these "non historic" looking ducts up the side of the building to get to the 10 foot mark? Are these buildings I see with louvers less than 10 feet just blatently violating code, or is there a provision I don't know about? Is a historic building built in the 1920's grandfathered in from meeting code? Any thoughts would be appreciated. Thanks in advance!