I was told that we are required to run plenum CAT 5e and RG-6 cable for a residential high rise project instead of pvc because the building is more than 5 stories tall. This is for the low voltage cable and telephone cabling within the individual units, not riser. As I understand it plenum wire is only required if the space above the ceiling is used for air return, which in this case it is not. Is this incorrect?