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Thread: Mastication

  1. #14
    Join Date
    Jan 2005
    Location
    Seattle
    Posts
    191

    Sealing the ducks

    robertee. I commend you for your efforts.It is a lot of work! But you can expect a lot more comfort and savings for you efforts.We have to seal with mastic all joint and seams per code.But what cracks me up is that you don't have to seal the elbow gores or the little holes in the boots and fittings(wys ext).But what I find most humorous is that you don't have to seal between the boots and the floor or ceiling.I use a skill saw when I cut out the floors because I can get a lot nicer fit.Reciprocating saws are a excellent
    tool BUT are not known for there precision.You should see some of the kinda square kinda 4"x10" or 12" 14"that get cut in on the new constrution around here.The amount of leakage here is quit large.
    Have a good day you guys.
    41GASMAN



  2. #15
    Originally posted by wormy
    I had one contractor tell me it won't hurt anything if conditioned air leaks under the house

    That seems to be the prevailing attitude of contractors in this area too. Commercial jobs all get mastic....it's required in the job spec. But for residential contractors just don't want to do it and maintain that it's not necessary.

  3. #16

    Post Octoberr 2005

    Originally posted by golf junkie
    Originally posted by wormy
    I had one contractor tell me it won't hurt anything if conditioned air leaks under the house

    That seems to be the prevailing attitude of contractors in this area too. Commercial jobs all get mastic....it's required in the job spec. But for residential contractors just don't want to do it and maintain that it's not necessary.
    Here in California effective this Oct 2005 all residential as well as commerical HVAC project require a duct test be performed by an outside independent contractor prior to passing inspection.

    If you change outdoor system only, duct test is still required...

    I'm sure everyone must know also that it will also be mandated that the indoor/outdoor units be matched not sure of that date.

    I give a plus to California they have always been one step ahead the rest of the country with thier energy conservation.

    This will help alot on situations such as the one in this post...
    AllTemp Heating & Cooling

  4. #17
    Join Date
    Jan 2001
    Posts
    7,945
    California is ahead of the rest of the country in trumping up new ways to increase fees and taxes and get business for shady contractors.

    What are they going to do about a house with a leaking takeoff on a duct system that is completely framed in and unaccessable..........yep...they will require the homeowner to rip their house apart and then let some fly by night buddy of the independant testing contractor come in and slap on a piece of duct tape that will undoubtedly fall off within a year........thats how california works...its a lot like the federal government.

  5. #18
    Join Date
    Nov 2004
    Location
    Thibodaux, LA
    Posts
    1,170

    Re: Octoberr 2005

    Originally posted by AllTemp
    Originally posted by golf junkie
    Originally posted by wormy
    I had one contractor tell me it won't hurt anything if conditioned air leaks under the house

    That seems to be the prevailing attitude of contractors in this area too. Commercial jobs all get mastic....it's required in the job spec. But for residential contractors just don't want to do it and maintain that it's not necessary.
    Here in California effective this Oct 2005 all residential as well as commerical HVAC project require a duct test be performed by an outside independent contractor prior to passing inspection.

    If you change outdoor system only, duct test is still required...

    I'm sure everyone must know also that it will also be mandated that the indoor/outdoor units be matched not sure of that date.

    I give a plus to California they have always been one step ahead the rest of the country with thier energy conservation.

    This will help alot on situations such as the one in this post...
    I have to say that is nice, and so is California.

  6. #19
    Join Date
    Nov 2000
    Location
    Waco, Texas, USA
    Posts
    6,153
    Why Why Why does everyone stress out about the duct joints leaking? The major leaks are where the ducts join the plenum and the equipment door panels, and around the supply ducts where they penetrate the ceiling/floor.

    I do not advocate putting a system together that can't be taken back apart. maybe the 557 is not the right tape but mastic is a mistake IMO. Code writers have went totally berzerk with this and now require it on the vapor barrier too which is completely ridiculous.

    http://www.achrnews.com/CDA/ArticleI...nalNews_Item/1,6084,128736-South,00.html






    [Edited by Steve Wiggins on 03-13-2005 at 10:17 AM]
    "And remember my sentimental friend......that a heart is not judged by how much you love, but by how much you are loved by others" - Wizard of Oz.

  7. #20
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    I don't have any trouble taking apart duct that's got
    mastic on it. (then again... the only time I ever have to
    take it apart again is if the homeowner remodels their
    home or I have to replace the hvac equipment.. no biggy
    either way) We use a brand called Air Seal... it works
    real good and the ducts come back apart without a ton of
    effort. I have seen some mastic that sets up like a hard
    epoxy coating or something, maybe thats the kind you've
    seen.

    I am very picky when it comes to air leaks in duct work.
    As I said earlier, the house sucks in the same amount of
    air your duct system leaks out. This not only leads to
    comfort issues (ask all the people around here that
    condemn heat pumps due to air leaks in their duct system),
    it also leads to mold/mildew/growth problems.
    ALL air leaks are important.

    I'm pretty sure someone is going to wonder about the 'new'
    addage... "They make houses so much airtite these days"
    In my opinion, the 'airtite' homes really need economizers
    put on the equipment to allow for fresh air to be brought
    into the house in a controlled / filtered manner.
    Albeit, selling a customer on this is kinda tough though...
    i.e. Customer spends thousands of dollars to get his house
    energy effecient... ala airtight
    HVAC contractor comes along and says...
    since you have such an airtight house, we need to install
    a fresh air intake on your system to bring in outside air.

    One of my duties at work is to do Heat Pump setup and
    preinspection. (trying to give short version of it)
    I had one very recent that measured 15% UNDER rated
    capacity. Not only did it reduce the unit from a 3.5 ton
    to a 3 ton.... it also introduced more moisture into the
    house, more dirt into the duct system, and so on)
    It had about 30ft of duct with the slips and drives not
    sealed.
    I had our installers seal it up with Air Seal.
    Now I have Full Capacity.

    Just by looking at the duct, it didn't look like it was
    leaking much. Especially being a tad bit oversized and
    the static pressure being on the low side.
    So the duct wasn't 'sucking that hard' to pull the air in.
    The air temp under the house was only about 50degree's too.

    HEre's another reason to seal your supply ducts...
    IN the summer, those air leaks are going to be blowing
    cold air into the insulation. The insulation has a
    foilback covering that helps prevent the air from leaking
    out there, so the air migrates to the stapled seams and
    ends where the insulation buts up to one another.
    Surface temp of insulation drops below dew point of
    environment its put in.
    Surface of duct wrap starts sweating.
    After an extended period of time, the moisture barrier
    (foil back) starts to become saturated. Then the
    insulation acts as a sponge absorbing the water. Then the
    insulation gets all soggy. Then it stops resisting heat
    transfer. and then and then and then muahahahahha
    Plumber crawls under house and comes out telling homeowner
    about the duct wrap is completely filled with water and
    falling off the pipes.
    Homeowner gets mad at hvac contractor cuz they spent
    thousands of dollars to get the job done and now its
    falling apart.




    Extend to others the grace that God has given you.

  8. #21
    Join Date
    Mar 2005
    Posts
    2
    Thank you all for your replies and input. I had another discussion with my HVAC installer and here is what I learned.

    In Washington State, it is common practice for the HVAC people to also insulate the ducts in the Western part of the state. Here in the Eastern part, the insulation people do it. No one can really tell me why this is.

    In terms of the tape they use to seal the seams, I am told this is code. They are still required to use something called "duct butter" (which sounds like mastic) wherever there is a metal-to-metal seam. He indicated that this will be done at the end of rough in because I guess this stuff is messy and gets on everything, so they do it last. Where the ducts come into the air handler are sealed with silicone, and not duct butter, because it is less messy. I didn't ask about sealing the area between the registers and the floor, but he did say that he covers all the registered after roughing in the system so that dust and crap doesn't get in there.

    I asked how the plenums are sealed and he said that they are not sealed in any special way. When the sheet rock is put in over the bays created by the 2x4s, this forms a tube that is fairly air tight. It doesn't seem very air tight to me, but I didn't push the point, since he is the professional and since he is going to do a blower door test to insure the system is well sealed after it is installed.

    In terms of the make up air (negative pressure) issue, he said that the system has a vent that runs to the air handler directly from the outside, with a damper that can be manually opened and closed. This damper will be calibrated at install based on the cfms of the various fans in the house, etc. The fresh air coming into the air handler will be filtered and then distributed through the house as needed.

    There is a good bit of Flex going in, so I asked him to address the rumors that this stuff has problems because it 1) can't be cleaned 2) collects moisture resulting in mold problems 3) can get holes that put a strain on the entire system, etc. Since this area is basically a high plain desert region, he said there isn't much of a moisture problem here. He wasn't sure what was meant about the system being "cleaned" but he said if the system is installed correctly and properly filtered, it shouldn't need to be "cleaned." Finally, he hadn't had any problems with the Flex being punctured except by rodents, which can also gnaw through hard pipe.


    BamaCracker: Yeah, mastication is the act of chewing… mastic.


    [Edited by soshin on 03-13-2005 at 07:29 PM]

  9. #22
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    Finally, he hadn't had any problems with the Flex being punctured except by rodents, which can also gnaw through hard pipe.
    I am seriously rolling in the floor laughin at this one.

    I'd hate to run into the rodents you guys have.
    I've never seen any kinda critter chew through metal pipe.
    That's gotta be the funniest thing I've heard in a
    long time.

    I can see Steve Earwin come across one in the Arizona
    Desert.

    "Here we have a Arizona Metal Mouth Rat... Isn't she a
    bute... Easy girl.. its alright... As you can see... it
    grows these massive teath that can chew your arm off in a
    matter of seconds. Its rumored these little ladies chew
    through ductwork, reaking havoc on central heating and
    cooling systems in these parts. I've even heard they can
    chew holes in dumpsters if their hungry enough"
    Extend to others the grace that God has given you.

  10. #23
    Join Date
    Jul 2000
    Location
    NW IL.
    Posts
    3,935

    Can Duct Tape Take the Heat?

    Check out this article at Home Energy
    http://homeenergy.org/archive/hem.di...98/980710.html

  11. #24
    Join Date
    Nov 2000
    Location
    Waco, Texas, USA
    Posts
    6,153

    Re: Can Duct Tape Take the Heat?

    Originally posted by MechAcc
    Check out this article at Home Energy
    http://homeenergy.org/archive/hem.di...98/980710.html
    That really pisses me off. No wonder duct tape was outlawed. It was misapplied in the test. Specifically the duct to plenum connection:

    1. Starting collars weren't used
    2. The gaps in the notches looked like a beaver installed it
    3. NO ONE is dumb enough to seal this connection with tape anyway.
    4. 50% of the tape was exposed to the air stream through the gaps....


    Goverment money at work.....
    "And remember my sentimental friend......that a heart is not judged by how much you love, but by how much you are loved by others" - Wizard of Oz.

  12. #25
    Join Date
    Jan 2005
    Posts
    24

    Can Duct Tape Take the Heat?

    I read the testing of duct tape and their conclusion that any tape is better for sealing duct work than duct tape. I wonder why someone doesn't make duct tape from black electricians tape? It's strong and sticky and a couple of layers should stay on for years. From my experience with duct tape their test results were right.

  13. #26
    Join Date
    Jan 2005
    Posts
    24

    Brother worried

    My brother recently had a new HVAC system installed. He asked the contractor about taping the joints. The contractor told him they usually don't tape joints but they would if he wanted them to do so. They do use lots of screws on the round joints. I told my bro about what I've learned on this list about sealing all the metal where air can leak and how ineffecient a system can be if it leaks. Now he is worried about his system. He has been under the house and looked it over but can't really tell anything with the insulation on. He is thinking about pulling some insulation and doing some DIY sealing. He has some sweating on his floor joist close to the crawl space vents and his space is dusty dry on the ground.

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