Are you referring to the returns vents for the HVAC system? Where will the three units be located in the house?

Yes, the return vents I believe they are called....these are the vents that are normally on the baseboard. The units are going to be mounted in the attic. Thanks for your help.

Return vents are too big to be installed on baseboard moldings. I think you are talking about the supply registers.

The return is usually installed on the wall near the ceiling. There should be no issue installing it in the ceiling.

Supply registers in the ceiling are a good placement for the AC, but not so good for heating. Cool air will sink, and warm air will rise. It will be more efficient in the summer, but less efficient in the winter. If the HVAC system is in the attic, then it is easier for the builder to install everything in the ceiling for the second floor. For the first floor it is more efficient if the HVAC systm is in the basement (assuming you have one), or on the first floor.

If you live in a warm climate this should be fine. If you are in area with cold winters, then you will be more comfortable if the supply registers are near the floor.

Thanks Mike_Home!

Yes, I believe they are the supply registers. We are building on a slab foundation so all three units will be in the attic. And I live in a hot, humid climate with mild winters (West Tennessee). I can see how the ducts will be shorter, and hopefully less expensive to install. Our builder said this setup is good for this climate (8 months HOT, 4 relatively mild) and it will be more efficient. He plans to build all houses this way going forward.

Thanks again!