Return Duct, up or down?
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  1. #1
    Join Date
    Feb 2004
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    So wifey wants to replace our "ugly" metal return air duct grate with a "fancy" carved wooden one.
    Fair enough.
    So I'm looking at it.

    The return grate is situated about a foot below the ceiling, actually, two of them are,
    in adjacent rooms (share the wall, vents not connected). Wouldn't it be better
    to be returning the cooler air from the floor level? It has to route it down to the crawlspace anyways,
    so it seems like a big mistake.

    I"m not a HVAC professional by any means but at face value, this is wrong, no?
    The house was built in 1960 and these are in two bedrooms.

    Any thoughts?

    This house does have central air, but that was installed quite a bit after 1960. It seems to me that in Chicago,
    heating would take precednce to return cold air than cooling would, to return the warmer air. Or, I'm nuts.

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    18,836
    The location of the return grille (up or down)has little effect on comfort or airflow.The supplies have a large effect.

    Now if they are using a single wall space as the duct,it may be too small,so moving it down the floor may be good.



    Those wood grilles can be too restrictive also,causing reduced air flow.

  3. #3
    Join Date
    May 2004
    Location
    Rapid City, SD
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    7,414
    Another bad thing about 2 vents sharing the same space like that is noise can travel right through there. Might not be a big issue depending on what the 2 rooms are, but it could also be a big deal if it's a bedroom and living room or something similar.

  4. #4
    Join Date
    Oct 2003
    Location
    west chester pa
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    343
    above eye level point up below eye level point it down

  5. #5
    Join Date
    Feb 2004
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    They share the wall, but on different sides of a stud,
    so they meet up at the "main line" of the return duct in the
    crawlspace. The question was more directed at the fact that
    the return is returning warm air, instead of "cold air"
    that it would suck up from closer to the floor.

    Perhaps I'm thinking too hard.

    I'll be sure to pick out a grate that has lots of open area.
    I may have to paint the inside of the duct though.

    Thanks for the responses.

  6. #6
    Having the return air opening high on the wall will work best for air conditioning since it will pull the warmer air near the ceiling. Sometimes low and high return air openings are installed with registers that can be opened and closed. This way, you can draw the warm air from the ceiling for A/C by closing the lower opening, or draw the cooler air from the floor by closing the higher opening.

  7. #7
    Join Date
    Feb 2004
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    yeah, that's what I was thinking.

    The stranger part is that this house has a 2nd floor addition,
    and upstairs, the vents are low to the ground.
    Now it seems to me that it's all reversed.
    Cause the 2nd floor is definatly warmer than the downstaris
    and downstaris is cooler. I'm wondering how much of an effect
    this has on the whole thing. in the summer, I pretty much close
    the downstairs vents off at the furnace so that the cool air
    mostly hits upstairs. That works well. I may look into
    cutting up the wall and adding bottom vents.
    Might help with heating.

    Then again, American Idol is on, maybe I'll do that later.

  8. #8
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    18,836
    Supply aur grilles have consideable "throw" by design ,that create air currents that along with convection(due to temp diference),move 10 to 20 times the cfm actually delivered to the room.

    Return air grilles are sized to move the air much slower,creating very little air movment in the room,there is no temperature difference involved.There location high or low has little effect on comfort in the room.Think about it,even with a return in every room,a high return doesn't create enough air movement to pull warmer air from the other side of the room.


    Now,with your two story home,if you want even temps on both stories,year round,you need two systems or two zones,or at the very least ,manual dampers to regulate the air flow to each story ,depending on the season.

  9. #9
    I think jpicasso has it figured out now. As with most multi level homes, you must adjust the air flow to different levels depending upon the season, i.e. heating or cooling. I know that here in MN there are many multi level homes that have that exact problem and that is the best way to get what you have to work without major changes. As far as the returns being high or low, it plainly does matter- warm air rises, and cool air falls. By having them high, they will draw in the warmer air, by having them low they will draw in the cooler air. The temperature difference may not be that great but when you get into 2 stories, I can vouch for the fact that they work much better in the high position due to the fact that the warmer air will always gather in the 2nd level. And usually the return is placed opposite the supply in any given room to draw the air through the room. Also, you can only put into a room what can be taken out. If you have a sealed room (box), and force air into it, the actual flow will depend on what is taken out, otherwise all you would have is a pressurized room (box).

  10. #10
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    As for a two storty ,I agree,returns on both floors and in each room allowed,or a return path from each room.

    As for high or low on each floor,I tried in my own home(12 years ago) as that's what I'd always heard,it made no difference.
    My last post regarding this,is basically a quote from Manual D regarding high/low returns,and I've found it to be true.But we can agree to disagree.

  11. #11
    Join Date
    Jan 2002
    Location
    Ft.Worth,Tx
    Posts
    4,584

    Cool Wood grills

    I don't know if you have a source for grills but,I would leave them where they are if working correctly.

    1-800-9-Wood-ja
    1-800-996-6352

    Models you are looking for WRG,
    Mitered Corners
    Opposed Blade Volume Dampers
    Standard & Custom Sizes
    Various Frame Styles
    Red or White Oak

    Factory for other hardwoods
    "Everyday above ground, is a good day".
    "But everyday that you have made a difference in someones life, may insure you stay above ground a little longer".<aircooled>

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