I am working on a TI (less than 1000 sq. ft) in which some walls move a couple feet and some office spaces get smaller or larger by 20 sq. ft. or so. No change to overall square footage and no natural ventilation. The existing single zone forced air system only had 2 return air ducts. Will I be required to add return air in each separate office space? Can louvered doors work as an alternative? I'd like to know the CMC section for more information, exceptions, etc. Thank you.