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Thread: Cold Air Return

  1. #11
    Join Date
    Aug 2007
    The Great White North

    Default Re: Cold Air Return

    Quote Originally Posted by Robert Larson View Post
    I'm finishing the basement and it's time to run additional heat runs and install cold air returns. I know that each room downstairs needs a cold air return. My question is, can I simply cut a hole into the exsisting cold air returns that already service the upstairs or do I need to connect directly to the main run? Would utilizing the exsisting main floor runs have any negative effect on the system?

    No ... you shouldn't tap into any existing ducting as this will affect the supply or return air flow intended for that space.

    Tap into the main trunk for the ducting and run them toward floor level for them to be effective. Likely you wouldn't need anything larger that a 5 inch duct line.
    If the furnace and ducting is located in the basement .... it should be easy to do.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  2. #12
    Join Date
    Aug 2008

    Default Re: Cold Air Return

    Quote Originally Posted by Langtry View Post
    I have a pre-fab home with a forced air furnace in the basement and one cold air return in the dining room. A previous owner finished the basement and added a cold air return in the basement (about half the size of the upstairs one).

    I notice that most of the cold air from upstairs simply flows down the stairs (which are only 10 ft away from the cold air duct). As a result my basement is usually cold.

    Would there be anything wrong with simply closing the upstairs return and putting a grate directly on the furnace intake downstairs? Thus drawing all of my cold air out of the basement? It seems to me that this would do a much better job of circulating the heat.
    YES, big problems with that! Aside from the efficiency of your furnace, you would also draw in underground contaminants, such as radon gas, etc. You can install a heat run in the basement, but it should be sized by conducting a static pressure test. Seal the return in the basement and install additional returns in the living area if necessary. Also seal all joints in the return with furnace mastic to prevent drawing air, as well as magnetic tape or duct tape over the filter slot.

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