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  1. #1
    Join Date
    Feb 2004
    Location
    Connecticut
    Posts
    1,661

    Insulating duct work - inside or out?

    OK, I am curious how Y'all insulate your duct work on installs: Do you wrap it on the outside, or do you line it on the inside?

    Let's here where you are and how you do it.

    I am in Connecticut, and it is mostly wrapped on the outside. However, when I lived in Kansas, it was all insulated on the INSIDE, before it was put together and taken to the job site.

    Which brings me to another question: Do Y'all build your duct work on site, or do you do it at the shop, and then bring it to the jobsite?

  2. #2
    Join Date
    Apr 2001
    Location
    Camel City, NC
    Posts
    6,232

    Insulation

    This came up at the CE Class I atteneded on saturday. We have to use R8 now on supply ducts. Some are mixing - liner and wrap. Some are using 2" R8 liner. Some are just wraping. Some use 2" duct board, mostly at the coast. Those ducks are getting bigger with that 2" liner and metal isn't cheap. I did hear someone say that the R8 wrap didn't look good (saging) due to the weight. Pins were the only thing that helped.
    Be safe not fast. body parts don't grow back

  3. #3
    Join Date
    Feb 2006
    Location
    Taylors, SC
    Posts
    403
    Almost everything we do is external wrap. I dont like internal liner in a res. duct system.
    Poor planning on your part doesn’t necessarily constitute an emergency on my part.

  4. #4
    Join Date
    Nov 2007
    Posts
    388
    We wrap supply...always! Sometimes we'll line the return ducts for sound attenuation for conference rooms, etc.

    I think that a fiberglass liner exposes you to all kinds of liability issues....from mold growth to fiberglass particles linked to cancer.

  5. #5
    Join Date
    Nov 2004
    Location
    Georgia, USA
    Posts
    10
    I wrap, But when I need to control noise, I usually line the inside and use felx duct. As for the sagging R8 I usually wire ty the insulation to control this.

  6. #6
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    5,355
    Due to the roughness factors liner affects system performance. It's actually sold a acoustic liner not insulation, although it does have some insulation qualities. I also have seen liner fall and block duct work. All glues fail in time and pins break off.

    There is a fairly new product I read about designed to replace acoustic liner w/o some of the liners problems. Maybe someone remembers what this is. I think I saw an ad in a trade mag.
    Tracers work both ways.

  7. #7
    Join Date
    Feb 2006
    Location
    Float'N Vally, MS
    Posts
    1,776
    Quote Originally Posted by selfemployed View Post
    This came up at the CE Class I atteneded on saturday. We have to use R8 now on supply ducts. Some are mixing - liner and wrap. Some are using 2" R8 liner. Some are just wraping. Some use 2" duct board, mostly at the coast. Those ducks are getting bigger with that 2" liner and metal isn't cheap. I did hear someone say that the R8 wrap didn't look good (saging) due to the weight. Pins were the only thing that helped.
    We haven't been forced to this yet.... But I hear your pain!
    This area is almost 100% ductboard in resi....
    We have found a ninch with metal wrapped on the outside for IAQ.


    I used this at our house for a test (and it works great).
    Will this fly with your "code"????

    http://www.insulation4less.com/prodex_Ffmf.asp
    Life is too short, Behappy!
    TFMM

  8. #8
    Join Date
    Apr 2001
    Location
    Camel City, NC
    Posts
    6,232

    behappy

    I asked about it and the answer was. Show in writing it is R8 and no problem. Yes duct spacers can be use to get R8. Only one person in class (30) said they didn't like it. Don't know how many have tried it though.
    Be safe not fast. body parts don't grow back

  9. #9
    Join Date
    Feb 2006
    Location
    Float'N Vally, MS
    Posts
    1,776
    Quote Originally Posted by selfemployed View Post
    I asked about it and the answer was. Show in writing it is R8 and no problem. Yes duct spacers can be use to get R8. Only one person in class (30) said they didn't like it. Don't know how many have tried it though.
    I agree we have started using bubble wrap in resi, not commerical (yet).
    But the above product is "R-14" and not bubble wrap. It is a little stiffer to put on and pricer.
    Life is too short, Behappy!
    TFMM

  10. #10
    Join Date
    Apr 2001
    Location
    Camel City, NC
    Posts
    6,232
    Sorry I missed the R-value in the literature. Thanks for the link.
    Be safe not fast. body parts don't grow back

  11. #11
    Join Date
    Dec 2007
    Location
    Frognot TX
    Posts
    836
    If it needs to be insulated, we always line it, and shop build, make a quicker easier installation. We glue and stud weld it in place, haven't had any come loose yet. It does make the system much quieter, and there will probably be some kind a lawsuit someday,the lawyers just haven't figured it out quite yet.

    There was a want ad in the Dallas Morning News from a law firm looking for furnaces that were installed in the '60's, so guess they've figured out how to sue somebody for 40 year old technology.

    The road goes on forever and the party never ends!

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