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Thread: Mastication

  1. #1
    Join Date
    Mar 2005
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    2
    I am in the middle of a residential construction project where they have just started putting in the HVAC system. I am talking to the installer about how important it is that the system be sealed well, that I want a blower door test once everything is finished, etc.

    The topic comes around to how they are sealing the seams, particularly on the hardpipe and around the joints. He told me that the joints were screwed then taped using a UL 557 product. He said this worked well and that they try not to use mastic much because mastic takes too long to dry and that the insulation guys just end up pulling it off anyway when they put their insulation on. I went down in the crawlspace and sure enough all the seams that I could see were sealed with this tape. I would like to get your opinion of whether screwing then taping is enough or if I should insist on mastic. Thanks.

  2. #2
    Join Date
    Feb 2003
    Location
    Huntsville,AL
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    4,125
    depends upon the product & applyer --

    my original ducts were sealed in 1974 with duct tape, which I can not now remove -- but, just the joints of the supply ducts. said tape has not fallen off anywhere.

    however, no seams nor plennum holes were sealed. I have since applyed mastic with a putty knife.

    so, why not schedule the insulators 3- 5 days later?

    does the tape have a metal backing? I used some to seal the insulation around pipes in the attic -- seems to be quite sticky -- but I will not be here 25y to judge --

    if rest of job is ok, then that will be ok.

    what about the plennum seams & holes? were the cracks around the register boots caulked -- between the boot & ceiling | floor ?

    one can do a duct leakage test --

  3. #3
    Join Date
    Oct 2003
    Location
    Illinois
    Posts
    549
    What is this "Insulators" talk? The installer is suppossed to do that. Screws and 557 tape is good enough. I guess if you wanna be on the bad side of the installer you can opt for mastic, just dont expect a nice answer.

  4. #4
    Join Date
    Jan 2005
    Location
    Seattle
    Posts
    191

    Exclamation Duct sealing

    soshin.Useing duct tape is not OK on a new system anymore.557 is just ducttape of a resonable quality.PLEASE PLEASE PLEASE do a "search" on sealing ducting and proper insulation.There has been a lot of threads on this subject.You just got to.you would not believe the differents it make to the performance and efficiency of your brand new system.As far as getting the mastic pulled off when the insulaters do their thing.Thats a bunch of toe jam.I seal all joints and the seams on all the hard pipe.Jump on the search feature here.Stay up burning that midnight oil.You have a lot of inportant things to learn and have done.Good luck if we can help,ask away.You need to make sure they do a good quality job on your install.But first you need to know what a good install consists of!
    41GASMAN



    [Edited by 41gasman on 03-10-2005 at 10:10 PM]

  5. #5
    Join Date
    Oct 2004
    Location
    PDX
    Posts
    4,917
    There are Mastic tapes avaialble that contain metal backing and mastic all in one tape. This stuff does last a ling time so there is nothing to worry about there. Plus the mastic is mess and does not look good and takes forever to apply. Not sensible in the slash and bang rates that new construction bid are brought down to these days..

  6. #6

    Post 7d16809

    Originally posted by soshin
    I am in the middle of a residential construction project where they have just started putting in the HVAC system. I am talking to the installer about how important it is that the system be sealed well, that I want a blower door test once everything is finished, etc.

    The topic comes around to how they are sealing the seams, particularly on the hardpipe and around the joints. He told me that the joints were screwed then taped using a UL 557 product.
    If I am not mistaken 557 has a UL Listing but has a warnign Not A To Use On Sheet Metal ...

    UL 181B-FX listed product - The Underwriters Laboratories, Inc. for closure systems for use with flexible air ducts and air closures. Possesses excellent shear properties. Superior quality, performance, and tensile strength. Shows excellent resistance to mold growth, humidity, flame spread, smoke generation, and the effects of high temperatures.



    [Edited by AllTemp on 03-10-2005 at 11:21 PM]
    AllTemp Heating & Cooling

  7. #7
    Join Date
    Aug 2003
    Posts
    1,841
    Originally posted by albowrx
    What is this "Insulators" talk? The installer is suppossed to do that. Screws and 557 tape is good enough. I guess if you wanna be on the bad side of the installer you can opt for mastic, just dont expect a nice answer.
    & plan to pay more for it.

  8. #8
    Join Date
    Jan 2005
    Location
    Seattle
    Posts
    191

    Smile masicification

    framehvac.
    Plan to pay more for what?Mastic on all galvinized to galvinized pipe or fitting is code here.
    41GASMAN

  9. #9
    Join Date
    Oct 2001
    Posts
    6,071
    "Mastication" is the act of chewing.

    Just thought you would want to know. . . . .
    Hindsight is NOT a plan!

  10. #10
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    In all fairness...
    you should have discussed the installation practices with the contractor doing the hvac work before agreeing to have them do the work.

    i.e.
    contractor #1 gives quote... its real high...
    contractor #2 gives quote... its real low...

    you think you get the same quality work
    So you choose #2

    however, there are differences in the
    quality/installation practices....
    contractor #1 goes out of his way to do fine quality work
    contractor #2 puts in flex pipe, does not balance air flow, etc

    Once job is halfway done.. you become more educated as
    to 'proper installation practices'.... you want
    contractor #2 to do the same quality work as contractor #1
    but you've already agreed to do the job, and more than
    likely don't have a written agreement as to the quality
    and standards of the work to be done.

    ---------------------------------------------


    Its been a long time since I've been to this board.
    Too bad it was with a sour post.
    I hate to hurt anyones feelings or anything.











  11. #11
    Join Date
    Jan 2005
    Location
    Seattle
    Posts
    191

    Talking

    Feelings......yea you hurt it.Damm nowmy feeling is gone.And it was the last one I had too!
    41GASMAN

  12. #12
    Join Date
    Jan 2005
    Posts
    24
    I'm one of the DIYs on the list and have gained a lot of knowlege here. I've been sealing all my joints with mastic and silicone. I went to several wholesalers and they don't even sell mastic. So you know the quality of work done in this area. I bought mine from Home Depot, expensive. The boots and elbos have so many joints with air leaks they have to be sealed. I even sealed the long joint in the round pipe. I want my system to be air tight. It is time consuming to use mastic but it comes in a caulking tube, more expensive at HD. I had one contractor tell me it won't hurt anything if conditioned air leaks under the house. I don't see him on this talk list.

  13. #13
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    I had one contractor tell me it won't hurt anything if conditioned air leaks under the house
    Now thats funny.


    Think of your house as a 2 litter plastic Coke Bottle.
    Put your mouth to it and start breathing.
    You are in essense a central air unit.
    Your unit sucks the air out of the bottle and blows the same amount back in.
    Now suck in a good bit of air, blow most of it back in and a little bit outside the bottle to similate a supply air leak.
    It wont take long for the bottle to start collapsing because its running out of air.
    Poke holes in the bottle to simulate air leaks in the house. i.e. PUll down staircases, light fixtures such as recessed lighting, recepticles along the outside walls.
    Now all the air you blow outside the bottle gets replaced by the 'unconditioned'/unfiltered air outside the bottle.

    In short... The air you blow under your house gets sucked back in from your attic. How would you like to suck in 120degree air into your house in the summer?




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