Any HVAC contractors out there?

[The Bad Guy]

I'm in the final stages of signing a contract for my house. The builder wants to put the registers/returns near the floor for my central air and forced hot air. To me, that seems absurd because the cold air is never going to rise in the summer and the house will still be hot.

I suggested that they put the hot air ducts in the same spot, but move the cold air ducts in the ceiling.

Is this a real feasible thing to ask? Is it real difficult to pull off? I figured they should be coming from the same duct, but since we are putting the central air, furnace and tankless hot water heater in the basement in a utility room, we didn't know how difficult this would be to do.

I'm meeting with a different HVAC guy tomorrow and didn't want to ask something like this if it was real unreasonable.

Thanks in advance for any help.

[Bugeater]

Having separate ductwork for each system would be virtually impossible since your AC uses the same blower that's in your furnace and the evaporator coil is installed in the plenum coming off the furnace. You would have to install a self-contained AC unit and twice as much ductwork to accomplish that, and the cost would be astronomical.

[bobbymitch]

Originally Posted by The Bad Guy

I guess that's what I'd be trying to accomplish.

Wouldn't there still need to be different duct work though?

No. There still would be the standard separate supply and return lines. The only difference is in each room of concern, you would add an additional supply register (ones that can be open and closed), one above the other; there would be one near the floor and one near the ceiling. The conditioned air would still run up in between the studs in the wall, the main difference is where the air is released into the room.

Just as many supply ducts can be diverted at the air handler to divert air mainly upstairs or downstairs for cooling and heating, you open or close the room register(s) to supply the air either high or low. The added cost is the labor to cut an additional hole in the drywall and the actual register.

[Cannibal]

Both hot (furnace air) and cold (A/C) air come from the same blower as Bugeater stated.

Our supply registers are all floor mounted and it it not really an much of an issue. We typically close the basement registers though as the temperature remains relatively constant due to being mostly underground.

As Brock stated, if you have a basement, routing all ductwork compactly and exposed where possible in service areas like the laundry (where the floor joists are likely exposed anyway) is the most economical way to go.

[The Bad Guy]

Originally Posted by bobbymitch

No. There still would be the standard separate supply and return lines. The only difference is in each room of concern, you would add an additional supply register (ones that can be open and closed), one above the other; there would be one near the floor and one near the ceiling. The conditioned air would still run up in between the studs in the wall, the main difference is where the air is released into the room.

Just as many supply ducts can be diverted at the air handler to divert air mainly upstairs or downstairs for cooling and heating, you open or close the room register(s) to supply the air either high or low. The added cost is the labor to cut an additional hole in the drywall and the actual register.

This is exactly what I want to pull off. The builder is pricing it out to include twice as many registers. I think it was like 15 per register, so it won't be that much additional.

Just have to see if the HVAC guy can do it.