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Thread: AC in attic?

  1. #1

    Default AC in attic?

    My daughter is considering buying a small ranch which has hydronic heating and thus no ductwork. Is is possible to install an AC unit in the attic with smaller vents placed in the ceilings of the rooms below? Are there any special units for this? Certain brands? The house is in northern Ohio so the ac is only necessary for a maximum of 3-4 months/year. Thanks.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    You can do this. You could put an air handler up there and the compressor outside. If you go with high-velocity ducts, the outlets are small. An alternative that works if the layout is fairly open is a split system. This has a unit with (usually) multiple compressors mounted outside, and indivdual fans and evaporators inside. Some can handle up to three zones. The units do take up some wall space, but are quiet since they only contain the evaporator and an air circulator fan. Often, they are mounted high on the wall and are controlled via a remote that also acts as a thermostat.

    Putting the compressor in the attic isn't probably a great idea, it's already hot enough and it gets inefficient dumping the waste heat up there. It could be mounted on the roof, but servicing is tough and the roof may not be designed for the weight along with a snow load.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Senior Member burleymike's Avatar
    Join Date
    Nov 2008


    It is done all the time espically in the southern states. I have done a few of them. The only hard part is getting the air handler up there sometimes you have to increase the size of the attic access. Of course the duct work needs to be insulated since the attic is not conditioned.

    You might consider installing heat strips in the unit for a backup heat if the main system fails. Of course this depends on the electric service coming into the house. Just a thought.

    Be sure to get several bids from independant contractors. A lot of those big chain type plaes have big chain type prices.

  4. #4
    Engineer Furd's Avatar
    Join Date
    Jul 2007
    Wet side of Washington State


    Air handler and ductwork in the attic along with registers in the ceiling is common. The condensing unit (compressor) will be mounted outside on the ground.

    Be careful if you decide on using a high velocity system as they tend to be noisy unless carefully designed and installed.

    You absolutely MUST have a heat load calculation done to properly size the unit. Oversized is usually worse than undersized because it will not properly remove the humidity.


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