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  1. #1
    Join Date
    Jul 2008
    Posts
    2

    Question Add Cold Air Returns

    I am installing air conditioning to my 1916 home. To do the remodel correctly we need to install cold air return vents and duct work in the second floor ceilings. My contractor proposed running the duct up a first floor wall then finishing a wall around the new duct. I would LOVE it if there is a way to install the cold air returns to the second floor without changing the footprint of the first floor! Is there any duct out there that would fit inside a wall? There is an interior wall that has plumbing in it. I appreciate any expertise you all can share. Thank you.:

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Add Cold Air Returns

    we need to install cold air return vents and duct work in the second floor ceilings. My contractor proposed running the duct up a first floor wall then finishing a wall around the new duct.
    It sounds as though the air handler is either in a basement or the first level .....Why are the vents for the second floor going to be in the ceiling?

    In order to have the needed air the ducting to and from the air handler will need to be a certain size. The size of this duct will be dependant on the amount of air volume required for the system to operate properly.

    Typically the size of ducting may be around 5 - 6 inch diameter which won't fit within a 2 x 4 framed wall.
    It's very common in retrofit installs where the ducting will be out in the open and later be boxed in..... sometimes it's the old ...... can't have your cake and eat it too ..... scenario.

    However ... depends on how much you are willing to spend tearing open walls the ducting might be changed to a rectangular type of duct work ... 4 x 10 for example.

    There may also be obstructions like beams , or joists that might prevent the duct to be located in that area.
    Also where you might think the duct would be better may not end at the optimum area above.

    Of course this all sight unseen .

    Just some thoughts.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Jul 2008
    Posts
    2

    Post Re: Add Cold Air Returns

    Thank you for your thoughts! Yes, the air handler would be in the basement. Supply ducts already exist on the second floor, it's the return ducts that need to be installed. The ceiling is the best place for those? Any more advice about a return duct that might fit into an interior wall? Thanks again!

  4. #4
    Join Date
    Dec 2007
    Location
    MN
    Posts
    455

    Default Re: Add Cold Air Returns

    So is this a central heating furnace with A/C?
    If that's the case then you should have 2 return vents. One low for the heating and one high for A/C, otherwise if it's just A/C then the higher return vents will work providing the supply vents are on the floor.
    Putting the ducts in the wall maybe a problem like Canuk mentioned.If the home is constructed using platform framing you will have obstructions in the wall from the top plate of the wall framing. That's why it's common to have the ducts run outside the walls and box them in doing a retrofit.

  5. #5
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: Add Cold Air Returns

    Use oval Duct, it is made to fit inside a wall. Good Luck!!!

  6. #6
    Join Date
    Feb 2010
    Location
    Iowa, Quad-Cities area
    Posts
    129

    Default Re: Add Cold Air Returns

    You don't need any RA to the second floor. We A/C here (older homes) quite well without. The most important thing is getting enough air there in the first place. Tranfer grilles can be installed if the doors are going to be closed. Remember, air takes the path of least resistance. Oval pipe in the wall is worthless.

  7. #7
    Join Date
    Feb 2010
    Location
    Iowa, Quad-Cities area
    Posts
    129

    Default Re: Add Cold Air Returns

    I forgot to add..........no offense to Sten.

  8. #8
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: Add Cold Air Returns

    Quote Originally Posted by Bob Gabrilson View Post
    I forgot to add..........no offense to Sten.
    Non taken, but do you think those rooms without the returns will dehumidify? All you do is dump cold air on warm air without returns, not efficient.

  9. #9
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: Add Cold Air Returns

    Quote Originally Posted by Bob Gabrilson View Post
    You don't need any RA to the second floor. We A/C here (older homes) quite well without. The most important thing is getting enough air there in the first place. Tranfer grilles can be installed if the doors are going to be closed. Remember, air takes the path of least resistance. Oval pipe in the wall is worthless.
    Could you explain why oval in the wall is worthless???

  10. #10
    Join Date
    Feb 2010
    Location
    Iowa, Quad-Cities area
    Posts
    129

    Default Re: Add Cold Air Returns

    We all agree (those who know) that the return should be sized larger than the supply. .1 static when sizing supply and .08 when sizing the return. I'm saying (my belief) is that air will take the path of the least resistance. That's why the dampers are in the supplies to balance were the supply will go. If there are enough returns and you add a 6 inch oval duct
    (80 CFM? at best) what good is it really going to do? I would install a 14X6 transfer grille if possible. Cheaper and roughly 160 CFM.

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