I'm just starting a new home.... approx 3,000 sq. ft., single story, nine foot ceilings, zoned: 3 ton & 2.5 ton Trane XL19 units. Have searched this forum, but not found anything that addresses my concern. Duct-work layout will all be hard-pipe and insulated, designed by Trane......but, is there any advantage or disadvantage to placement of the return air for the air handlers ? Get mixed answers from contractors concerning whether they should be low, wall-mounted, or located in the ceilings. Presently all are located in the ceilings, one in each bedroom and one in each hallway at opposite ends of the house. Living in N.E. Texas, my cooling season is longer than the heating season ( usually seven cooling, four heating, and one using nothing at all. This is a fantastic forum and hopefully I can arrive at a concensus of how you professionals feel about the matter. Thanks for any help that you can offer.