Got a call to install an evap. coil and a/c in a modular. Total square foot about 1300, 2 x 6 walls, minimal windows, new house. The factory installed a 4 ton blower in the a/h with 15 kw. There are a total of 6, count them SIX vents 2 1/4 by 12. Also r32 in attic. No adding new vents. Return is 20" flex.