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  1. #1
    Join Date
    Aug 2008
    Posts
    20

    Anti-Rodent Flex Ducts

    I currently have old, decrepit ducts in the crawlspace, but I got a bid (which I accepted) from an HVAC company to put the furnace up in the attic, as well as new ducts. After reading this forum, it seems that rats like to use flex ducts for their nests. Well, the area I live in has lots of roof rats, and there have been previous infestations in my attic. They are gone, and I have covered all holes I believe, but you never know, so what I was wondering is are there different types of flex ducts available? Can I request that anti-rodent flex ducts be used? Is there anything additional I can do, like for example wrap the ducts in steel wool? Or maybe they sell some kind of steel wool product which can slip over ducts? Thanks.

  2. #2
    Join Date
    Jan 2008
    Location
    s chester county,pa
    Posts
    144
    or wrapped metal duct.

  3. #3
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,139
    you can wrap the ducts in hardware cloth a metal 'screen' with small holes.
    labor intensive, lots of cuts on your hands!
    but while you are doing this...check the seal of the duct take offs on the plenum.
    they should be mastic sealed...not duct tape.
    and perhaps the hvac co could install the hardware cloth..and properly seal the ducts also. You haven't installed yet, and there would be an upcharge for doing work
    that is 'unusual'. but worth the time effort & $$.
    are you 'hands on' kind of yoyoma?
    I'm not sure where you live..but use R-8 ductwork and STRAP ducts off attic floor.
    I recently had a client that the unit in the attic was uninsulated...make sure
    that the unit is for unconditioned space. The client with the uninsulated unit
    has mold inside the unit.
    ducts lying on top of insulation condensate, and should be properly strapped off attic floor. Check your code requirements.
    best of luck!
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  4. #4
    Join Date
    Aug 2008
    Posts
    20
    check the seal of the duct take offs on the plenum.
    they should be mastic sealed...not duct tape.
    The person who went over the bid with me told me they don't use duct tape so that's good they know not to do that.

    are you 'hands on' kind of yoyoma?
    Not much, but I wouldn't mind paying a reasonable upcharge to get hardware cloth added to the duct work.

    but use R-8 ductwork and STRAP ducts off attic floor.
    I'm in a moderate climate, doesn't snow, and hot for only a few weeks of the year. The bid is for an R6 ductwork system. Since I'm in a moderate climate I thought R6 would be fine. While this is being done, the ceiling will be vaulted over the dining room, living room and kitchen areas, with just enough space for the ductwork, insulation, and space for ventilation. I told the contractor I'd like a metal grate at both ends of the vault so rodents will not be able to enter. I'm a little worried as this space won't be accessible at all so I won't be able to inspect the ducts in the future for tears etc. I will tell them to strap the ducts off the attic floor in the other areas of the house. Thanks.

    make sure that the unit is for unconditioned space.
    What do you mean? They have units for conditioned space and unconditioned space? How do I tell the difference? Thanks.

  5. #5
    Join Date
    Mar 2007
    Location
    NW AR
    Posts
    2,478
    Why go to all the trouble of wrapping flex duct in "rat proof" material.
    Have him install metal ducting. Problem solved. Flex duct is junk to begin with. (That statement ought to stir up some shet.) I dont care how good the installation is and I dont care what everyone else on this site is going to say in argument FOR flex-duct, its inferior material. Period. It ovals out after time.

    By the time you wrap all your flex duct in this screenig, you could probably spend the same amount on a metal duct job. Plus rats are determined little sons of beeches, theres not much they cant chew through.

  6. #6
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,521
    Quote Originally Posted by ar_hvac_man View Post
    Why go to all the trouble of wrapping flex duct in "rat proof" material.
    Have him install metal ducting. Problem solved. Flex duct is junk to begin with. (That statement ought to stir up some shet.) I dont care how good the installation is and I dont care what everyone else on this site is going to say in argument FOR flex-duct, its inferior material. Period. It ovals out after time.

    By the time you wrap all your flex duct in this screenig, you could probably spend the same amount on a metal duct job. Plus rats are determined little sons of beeches, theres not much they cant chew through.
    I think almost everybody will agree that metal is better. Just most people don't want to pay for it. It does cost more. For rats, buy a cat. Leave it outside and don't feed it. It will take care of everything in the area. I feed my cat and he kills everything for 1 yard each way. Of course, he brings me most of his little "presents" for approval.

  7. #7
    Join Date
    Mar 2007
    Location
    NW AR
    Posts
    2,478
    Quote Originally Posted by bmathews View Post
    I think almost everybody will agree that metal is better. Just most people don't want to pay for it. It does cost more. For rats, buy a cat. Leave it outside and don't feed it. It will take care of everything in the area. I feed my cat and he kills everything for 1 yard each way. Of course, he brings me most of his little "presents" for approval.
    I used to think everyone thought metal was better. But just wait, keep checking this thread and youll see what im talking about. Its ludacris to me to think that anyone would consider flex better ducting, but believe me theres alot of pros on here that do.

  8. #8
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,521
    Quote Originally Posted by ar_hvac_man View Post
    I used to think everyone thought metal was better. But just wait, keep checking this thread and youll see what im talking about. Its ludacris to me to think that anyone would consider flex better ducting, but believe me theres alot of pros on here that do.
    Those are called "haters", they will ***** and complain about anything anybody says, no matter what. They are the type that would complain if you gave them a million dollars, wondering why you didn't give them more, rather than be grateful.

  9. #9
    RAts can eat throug most any thing, but if this is a on going problum with rats go with wraped metal duct. it will help out a lot their is no argueing over fex or hard duct in your case its simple hard duct is what your looking for, its the most rat resistence your going to get also make sure your contractor seals it with mastic. good luck with that

  10. #10
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    flwx is ok in most applications and goes a good job for the most part

    it is not as labor intensive and that is what makes it better for some people

    in your case with known rat problems flex duct should never be concidered

    hard pipe and wrapped with sleeve or bubble rap. The rats may pull the insulation off if they get back in the attic but getting through the pipe is hard to believe

    have your guy reprice the job running all metal with wrap

  11. #11
    Join Date
    Aug 2008
    Posts
    20
    Wouldn't wrapped metal ducts be a lot heavier than flex ones? Can they be supported in an attic without problem?

    Also, what is the "wrapped" part? Is that the mastic? Or is it insulation? Thanks.

  12. #12
    Join Date
    Jun 2008
    Posts
    63
    Quote Originally Posted by bmathews View Post
    ..... For rats, buy a cat. ....
    Cats eat mice. Rats eat cats. A good snake eat them all.

  13. #13
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,139
    so the cat would live in the attic?? better to nest snakes in attic??
    don't really think this is a 'fix' but a bandaid. (not to offend anyone...)

    the problem that I encounter with hard ducts is that they are not mastic sealed.
    again this is my area, but the longitutal seam where the sheetmetal connects to make
    this round duct is not sealed. nor or the 90's as the 'thinking' here is that it only leaks into the duct wrap. I find lots of duct leakage with hard duct...1.5 to 2 tons
    in new construction...higher in existing systems.

    as it is difficult for me to make my inspection before ducts are wrapped...I like flex.
    some hvac companies wait to wrap until my inspection. I'm sure they just LOVE me
    being so picky...LOL!
    the other leakage site is where the supply box rests on the attic floor.
    I seal these leakage areas from inside with mastic tape.

    there is little data to recommend foil bubble foil 'duct' insulation.
    a correct install has a spacer between hard duct and fbf insulation.
    like foam insulation there is a mis-use and mis-understanding of how these
    products perform.

    The only place I have seen it correctly installed was at La. house project
    and when I questioned the reasoning the building scientist said that it worked
    well because it was in a conditioned space.

    I recently was in an attic where the heating system was uninsulated.
    There are different applications for different systems. This system was
    for conditioned space. When installed in the hot humid attic mold was in
    the system, and plenum. Hot + cold = mold when a food source is present
    (the insulation in the supply plenum is the food source). Mold also requires light
    and the uv light and poorly sealed junctions allowed enough light to feed the
    mold.
    Had this system been inside the conditioned space..it would have not have been
    an issue. The hot attic temps caused condensation, if it would have been in
    the location it was designed to there would not have been the extreme temp
    difference, and it would not have been an issue at all.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

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