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  1. #1
    Join Date
    May 2010
    Location
    Phoenix, AZ
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    13

    Default Tips on sealing ductwork?

    Hey folks,

    I recently had a home efficiency audit performed on my house. The results were mostly good, but they did say that my ductwork needed to be sealed more effectively. Apparently, when they turned on one of my A/C units (I have swamp coolers), they were able to feel cold air pouring out through the roof at the point where the unit met the house.

    They quoted me about $700 to fix this (as well as seal around the, um... registers?). I don't know if this is high, but assume so since they also quoted me $1000 to add more insulation (something my boyfriend and I can do for ~$250 and a day of our time).

    Can anyone offer any tips on how to best seal up the inlet? I have access to both the roof and the attic side of the connection.

    Also, the silver casing on this tube is torn here and there. I can see the yellow stuff inside. Is that something I can simply repair with tape (not the dull duct tape, but the shiny stuff)?

    Am I better off just hiring someone?

    Thanks in advance for any help you can offer!
    -Ktty

  2. #2
    Join Date
    Jul 2009
    Location
    Northeast
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    661

    Default Re: Tips on sealing ductwork?

    Being in the North East I haven't done much with Swamp Coolers but, it should be sealed at the point that it's leaking. If yours is located on the roof you may be able to fix the leak with the same thing they use when installing rooftop units, sort of a rubber membrane with roofing tar or maybe some kind of silicone or glue. They also have the type that's sticky on one side but don't know the name. It's also hard to tell you what to do when we can't see the leak.
    As for the Ductwork there is no easy way to seal them if they're already insulated unless your willing to strip the main supply , or cut out sections where the two pieces come together, tape, seal it, and reinsulate it. If you decide to go this route use Duct tape to seal (silverback) and then use Mastic with a cheap paint brush or rubber gloves. Then Insulate after it dries, it dries pretty fast.
    It sounds like they used Flex duct for your supply runs so if it is torn all the way through you should replace it, if it's not all the way through and it's not a large tear you can use the silverback and patch it.
    If the insulation is pulled all the way over the supply boot and you can see no metal from the same your registers or ceiling diffusers should be OK.
    I don't know the extent of your leaks so I can't comment on the price but I also would advise more than one quote. We usually charge around $600.00 to tape seal and insulate Ductwork but that also depends on the total length to be done and access. It's cheaper to do a cellar that you can walk around in than it is to do an attic that your crawling in.
    In any case get a few more quotes and take it from there, it is always in your best interest to have all your exposed ductwotk taped sealed and insulated.
    Last edited by Sten; 05-22-2010 at 09:38 AM.

  3. #3
    Join Date
    May 2010
    Location
    Phoenix, AZ
    Posts
    13

    Default Re: Tips on sealing ductwork?

    Thanks so much for the feedback, Sten. I appreciate it.

    I did a little more investigation. The biggest leak was between the cooler itself and the metal housing that fed into the roof. I could feel cold air blowing out quite vigorously.

    At some point someone had put silver tape around the connection, and then at another point someone had put a tar & shingle-like substance on that. On the bottom of the connection, there were gaps that hadn't been covered at all.

    On the shingle/tar/tape that was leaking the worst, I simply cut it all off until I reached bare metal on both the housing and the cooler. Then I took HVAC tape and taped the heck out of it.

    Where there was just a little airflow through the shingle/tar/tape - or on the bottom where there was nothing - I didn't cut off the s/t/t, but did tape over the leaks. I made sure that the HVAC tape contacted bare metal to get a good seal.

    At the moment, there isn't any air blowing out of that connection anymore. Anything else I could have done/should do? The tar and such?

    Inside the attic, there is a little air leak where the flex duct meets the ceiling. I'm thinking that maybe Great Stuff spray insulation might work there??

    On the duct work (flexible) itself, there are tears in the silver casing - some approximately 18" long - but there isn't any airflow out of the yellow, internal insulation. HVAC tape to the rescue?

    For everything in the house - registers, vents, etc. - I got some caulk to seal that up.

    I called up a couple people to get me more quotes. They all wanted to charge me $150 to "test my system" before telling me how much to fix it.

    Thanks!!

  4. #4
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: Tips on sealing ductwork?

    You can tape the 18" tears and it'll be OK, as long as they don't go thru to the inside. Also keep in mind that older flex will tear more easily than new so you could end up doing a lot of patch work. If the boots that the registers, vents go into were installed and insulated right there shouldn't be any leaks. The insulation on the boot in a floor supply should go all the way to the sub floor, this will stop the same from sweating, same thing goes for a diffuser or ceiling supply. I guess if your trying to save money whatever works to stop the leaks is OK. You can't really blame the Contractors for wanting to test your system before giving you a quote as they don't know what there getting into, the old can of worms comes to mind. They also don't want to test your system and tell you whats wrong for free and then you fix it yourself, not to say that you would do that. There just protecting themselves.

  5. #5
    Join Date
    May 2010
    Location
    Phoenix, AZ
    Posts
    13

    Default Re: Tips on sealing ductwork?

    Thanks!

    Quote Originally Posted by Sten View Post
    I guess if your trying to save money whatever works to stop the leaks is OK.
    Well, I guess that is true. I do, however, prefer to do things as right as possible. The people who lived in my house before me had a 'whatever works' attitude when they remodeled a short while ago; consequently, I'm having to re-do wiring, plumbing, flooring, etc. My work may not be as pretty as a pro's, but I've had pros out who say they would be very satisfied if their people did the quality of work I do.

    It's not so much trying to save money - it's because I enjoy doing the work on my house myself. If I don't feel I can do a project myself (e.g. running a new gas line to my dryer) or it stops being fun (e.g. some electrical work in my kitchen), I head right out and hire someone.

    Quote Originally Posted by Sten View Post
    You can't really blame the Contractors for wanting to test your system before giving you a quote as they don't know what there getting into, the old can of worms comes to mind. They also don't want to test your system and tell you whats wrong for free and then you fix it yourself, not to say that you would do that. There just protecting themselves.
    I can totally understand that. My objection is that, in order to get 2-3 quotes, I have to pay 2-3 contractors $150 each for the testing because they won't use the other guy's results (I asked). So I'm out $450 before I even have any work done? I'm, obviously, not a pro, but my leaks weren't exactly subtle - you didn't have to put smoke in the system to tell where there was major airflow. So why not have the standard process be come out, turn on the AC, see if there are obvious leaks and if there are/aren't, THEN suggest more testing. That gives me a chance to evaluate the contractor and decide if I want to pay him for the test, or get another opinion.

    But... that's neither here nor there. Thank you again for your help. I appreciate it!

    -Ktty

  6. #6
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: Tips on sealing ductwork?

    A good HVAC Company would wave the $150.00 if you decide to go with them.

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