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  1. #1
    Join Date
    Dec 2007
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    5

    Should I close A/C vents in unused basement rooms?

    I am staying the summer in an old house (not my home) with a 2-year-old Lennox central A/C that has not been run for over a year.

    The A/C seems weak on the ground floor where I spend all my time. The house has is no second floor.

    Q#1. Should I close the A/C vents in 2 unused basement rooms?

    Q#2. Can you suggest anything else that I should inspect etc to improve performance?


    Thank you.
    BertB (ordinary home user, obviously not an HVAC professional)
    Last edited by BertB; 08-11-2008 at 01:25 PM. Reason: spelling correction

  2. #2
    Join Date
    Jul 2008
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    551
    are there returns in those basement rooms?

  3. #3
    Join Date
    Dec 2007
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    5
    The two basement rooms do not have return vents. Each basement room has two vents but they both emit cool air.

    There is a large return vent in the hallway between the two basement rooms.

  4. #4
    Join Date
    Jul 2008
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    IMO, no. Don't close them and I do base that opinion on this:

    http://www.consumerenergycenter.org/myths/vents.html

  5. #5
    Join Date
    Jan 2004
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    Lancaster PA
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    67,907
    Whens the last time the filter was changed.
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  6. #6
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    Quote Originally Posted by badtlc View Post
    IMO, no. Don't close them and I do base that opinion on this:

    http://www.consumerenergycenter.org/myths/vents.html

    Since these are supplies in a basement. That may have been installed more for heating reasons. He may get better cooling to his first floor by closing them, and not suffer from losses in that report.
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  7. #7
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    Jul 2008
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    Quote Originally Posted by beenthere View Post
    Since these are supplies in a basement. That may have been installed more for heating reasons. He may get better cooling to his first floor by closing them, and not suffer from losses in that report.
    That doesn't really matter. If you are losing conditioned air to spaces not to be conditioned like the study indicated, you are wasting energy. Seems like with the lower static pressure of having all the vents open, better air flow, etc. it should be a reasonable expectation.

    I made the mistake of closing vents when I first got my house. For my situation closing vents, including some the in basement, raised my monthly energy usage by 3%. I did a 5 wk study on my house alternating days with vents closed and open. My power company provides my daily power usage on the net along with high and low temps for that day. That makes it really easy for me to compare apples to apples.

  8. #8
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    Quote Originally Posted by badtlc View Post
    That doesn't really matter. If you are losing conditioned air to spaces not to be conditioned like the study indicated, you are wasting energy. Seems like with the lower static pressure of having all the vents open, better air flow, etc. it should be a reasonable expectation.

    I made the mistake of closing vents when I first got my house. For my situation closing vents, including some the in basement, raised my monthly energy usage by 3%. I did a 5 wk study on my house alternating days with vents closed and open. My power company provides my daily power usage on the net along with high and low temps for that day. That makes it really easy for me to compare apples to apples.
    Did you ever try it, by only closing vents in the basement.
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  9. #9
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    Quote Originally Posted by beenthere View Post
    Did you ever try it, by only closing vents in the basement.
    Yes. I had 2 vents in the basement and 1 vent in a bedroom. I tried closing them all, closing just the bedroom, and closing just the basement. The vent in the bedroom is bigger than most so it essentially equaled the 2 basement vents. The odd thing was the increase in energy usage was the same no matter how many vents were closed.

  10. #10
    We have a 2-story house with a finished basement, the furnace/air handler in an unfinished utility room in the basement. If I don't close off the basement registers in the cooling season, the basement gets very cold, and not enough cool air makes it up to the 2nd floor. So closing registers is a way to distribute the flow more evenly throughout the house (to compensate for the longer distance and working against gravity for the air to make it up to the 2nd story).

    Is there another way to do this?

  11. #11
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    If your ducts are in the ceiling in the basement. The type of ceiling(drywall/drop ceiling) will also have an effect.
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  12. #12
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    Quote Originally Posted by CleveRocks View Post
    We have a 2-story house with a finished basement, the furnace/air handler in an unfinished utility room in the basement. If I don't close off the basement registers in the cooling season, the basement gets very cold, and not enough cool air makes it up to the 2nd floor. So closing registers is a way to distribute the flow more evenly throughout the house (to compensate for the longer distance and working against gravity for the air to make it up to the 2nd story).

    Is there another way to do this?
    Not without zoning.
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