new HVAC vent placement

colorsofspringJune 7, 2007

We are in the process of sealing up rotting sub-slab HVAC ducts and installing a whole new furnace and duct system in our 2 story townhome.

One contracter walked thru our house and explained how the ducts would run and how the vents would be placed above closet doorways or in soffits along the ceiling. Since heat rises, I am concerned that our rooms would not heat efficiently during the winter with the ducts so high up. Is this a valid concern? The previous registers are in the floor! Our 18'X 12' living room is on the slab and is extremely cold in winter. Should we have more than 1 register in this room?

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IMO predomantly AC should supply from the ceiling. Predomantly heat should supply from floor. This is best case design. As long as the returns allow air flow across the room, it probably won't matter much. But if returns are above the supplys or absent, you will be unhappy with the job.

    Bookmark   June 8, 2007 at 12:06AM
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Our previous system used the same ducts for both heating and AC. I am assuming that it will be done the same way this time. We currently have 2 returns in the house. One at the bottom of the stairs and one at the very top of a the high ceilinged stairwell.

    Bookmark   June 8, 2007 at 12:13AM
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The BEST place to have a duct system is in conditioned space, such as what you described. The ideal place to have a single duct system is in the ceiling. You did not mention the duct location for the top floor. They should NOT be in the attic.

The return air duct size is VERY important. And, before the ducts are concealed, have them thoroughly inspected by the local code enforcement official.


    Bookmark   June 8, 2007 at 12:26AM
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CJ Mechanical of North jersey llc.

You will have cold feet unless you get heat low on a slab. But if this is not possible have low return to remove the cold air. I assure you will be wereing socks in the winter with just supplys high in the room.

    Bookmark   June 8, 2007 at 8:13AM
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Phillip: We have no attic - not even a crawlspace! To top it off we have a flat roof. Our top floor will also have the ducts coming out over doorways and near ceilings.
Coolmen: Our feet were very cold last winter so we have gotten used to wearing slippers and thick socks.

This is pretty much a nighmare scenario for us. We are first time homebuyers. The furnace and AC were installed new by the sellers because they were unable to sell with the 34 year old furnace that was previously here. We only discovered the rotting out sub-slab ducts 2 months ago, after heavy rains here in the northeast. We investigated and were shocked to see rotted out metal sitting in dirt with rocks exposed! Mold started to grow and we stopped using the heat because I am sensitive to the mold and my daughter started getting unexplained fevers. So basically, we are stuck with this huge unexpected expense of a new updraft furnace to replace the downdraft furnace and all new duct work. We have no idea how the upstairs ducts are routed behind the walls so we are running new ducts with soffits. We also have to seal off the floor registers with concrete. Wish us luck.

    Bookmark   June 8, 2007 at 11:38AM
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