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Thread: Attic ductwork

  1. #1
    Join Date
    Aug 2011
    Posts
    62

    Attic ductwork

    Hi: I'm trying to size a new upflow heater to existing non insulated sheetmetal system in attic. The old heater was removed from storm Sandy. I used a online calulater and got 49000 BTUS. There was no consideration for attic ductwork.
    Its only a 1000sf house and owner does'nt want to insulate ducts. Anyone know the addition heat loss from above ducts.
    thanks...

  2. #2
    Join Date
    Jun 2007
    Location
    Greenwood Indiana (Indianapolis)
    Posts
    420
    As much as 70% loss/gain, especially if its the return duct. Don't forget the ducts will sweat in hot attic this summer time.
    As iron sharpens iron so one man sharpens another Proverbs 27:17 NIV84

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,090
    Are you sure the duct work in the attic isn't insulated. it my be that its just the sheet metal in the utility room isn't insulated.
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  4. #4
    Join Date
    Jun 2000
    Location
    N. W., IN
    Posts
    1,017
    The owner may not want the duct insulated but that makes him wrong as you would be if you do the install that way.

  5. #5
    Join Date
    Dec 2012
    Location
    oklahoma
    Posts
    20
    might want to check your local codes . ductwork run in an unconditioned space isnt up to code around here.

  6. #6
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,042
    Quote Originally Posted by deadeye52 View Post
    Hi: I'm trying to size a new upflow heater to existing non insulated sheetmetal system in attic. The old heater was removed from storm Sandy. I used a online calulater and got 49000 BTUS. There was no consideration for attic ductwork.
    Its only a 1000sf house and owner does'nt want to insulate ducts. Anyone know the addition heat loss from above ducts.
    thanks...
    If he doesn't want to insulate, then he better be spray foaming the roof line.

    Otherwise you have a lawsuit when the drywall repair/mold abatement issues come about.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  7. #7
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,290
    I'd turn the job down if he doesn't want to do it right. Do you really want to oversize the furnace to accommodate uninsulated ductwork?

  8. #8
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,188
    sounds like the owner is not understanding why ducts are insulated.
    do you really want to do a job where occupants will never be comfortable?
    high utility bills, dripping ducts & no comfort?
    there will be alot of call backs on this kind of job.

    have to agree with ron:
    The owner may not want the duct insulated but that makes him wrong as you would be if you do the install that way.

    I'd walk away if I couldn't get the homeowner to understand.

    are you sure the duct isn't internally insulated??

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

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