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Heat Loss Attic Duct Work

kelld Member Posts: 1
I had a heating system replaced five years ago, two roofs and just found out heat is escaping thru the duct work in my attic.  One of the runs is attached between the roof rafters at the roof?  Is this code and can anything be done.  I had an audit because of severe water damage during winter months...Ice dams, leaks.


  • Jamie Hall
    Jamie Hall Member Posts: 22,877
    Don't know whether

    it's code or not, but it sure is common.  I presume this is hot air, and the ducts are metal?  The only solution is insulation -- lots of it.  There is a reason we in the hot water and steam fields use metal for radiators -- besides that it holds up well.  It is a wonderful heat emitter!  Those ducts, uninsulated, will cheerfully radiate 150 btu per square foot, or more.

    The more insulation the merrier.  Four inches would not be even remotely out of line; a foot might be more like it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gordy
    Gordy Member Posts: 9,546

     First of all is it insulated flexible duct work, or metal duct work that is not insulated.  As far as code it depends on where you live. Call the building dept. in your area, and ask. Some areas do inspect HVAC if a permit is pulled to insure it is properly done, and yes it is code to insulate duct work in an unconditioned space in most places.

     I would think an installer of any credibility that put duct work in an unconditioned space should know the out come if the duct work is not properly sealed, and insulated.

      Your problem besides the issues that have been caused by the poor workmanship is it has been 5 years, and I doubt any recourse is in the mist through the installer.  I would give him a ringy dingy to let him know how you feel, and the damage that has been done by his substandard work at the very least.  May be some other recipient of his work might get a little better job next time.

  • Brad White
    Brad White Member Posts: 2,398
    Start with the Walrus and Tupperware Rule

    (Punchline Deleted)

    Seal the ductwork to the nth degree before any insulation. You can lose more heat from one square inch of air leakage in a cold attic than almost 20 square feet of 1" insulated duct and almost 100 square feet of bare duct. Use a brush-on water-based acrylic mastic and seal longitudinal and circumferential seams and all screw penetrations. Every possible point of leakage.

    A tape and activator system such as HardCast is tops. Do that if you can. Virtually air-tight.

    Then, insulate. At least R8 is code in most states, but R30 would make me happy, sealed with a vapor barrier and taped.

    Do not use duct tape for duct sealing. It is actually prohibited in our (MA) state energy code to seal ducts, of all things.

    Duct tape dries and falls off, does not last. 

    (Unless it gets stuck in your daughters' hair. In which case yes, your daughter will be at the Second Coming and Jesus will walk up to her and say, "What the heck happened to your hair?")
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
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