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Foam = Rot

user-53644 | Posted in Energy, Heating & Insulation on December 7, 2006 08:26am

I usually spray icynene foam in all of my rim joist and cantilevers, thinking that this is superior to batts.  Recently I’ve talked with some remodelers and other builders who swear up and down that I’m creating a perfect situation for rot.

I could go on and on about the supposed reasons for and against, but I’m interested in some responses from people who absolutely know this product and can give me sound advice on this subject.  My goal is to produce a lasting product and right now I’m a bit undecided.

Thanks.


Edited 12/8/2006 2:47 am ET by Daiku-san

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  1. Piffin | Dec 10, 2006 01:26am | #1

    I can't imagine how.

    The only time rot happens is when somebody does something wrong to let water get trapped. but without knowing more about the cases where they noticed trouble, who can comment? The only clue I'd have is that icy is open celled so it can hold water - but how does the water get there in the first place, and become trapped? bad design ?

    you don't want to go on and on so it's hard to have a conversation about it.

     

     

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    1. DoRight | Dec 12, 2006 02:33am | #7

      I am not so sure about this.   I have actually had this thought before about foam.  It seems to me that if you get mositure into such a bay (cantilever, etc.) the moisture could be trapped hard up against your joist (between the foam and the wood).  With no air movement at all, I can see rot.

      Naturally, you will say "well you are not supposed to have water in there".  Fair enough.  However, what if it happens.  Suppose you flood the kitchen and the water runs over to that cantilever and into the foamed bay?  Or some other such occurance?  If the bay had been filled with FG, there would be air pockets and some air movement thus some drying out.

      Just a thought.

    2. Hackinatit | Dec 13, 2006 04:59am | #8

      So, water NEVER gets into any structure if it's prepared correctly?

      Hmmm...

      Never?

      Huh

      FWIW I bet it would be a real b!tch removing and repairing any "icy" installation that did get wet from a leak. Especially if there were a service drop, header and plumbing stack in the cabinet wall directly underneath. Lots of moldy goo to play in.

       

       

       Troy Sprout

      Socialism in general has a record of failure so blatant that only an intellectual could ignore or evade it."-- Thomas Sowell

      1. Piffin | Dec 13, 2006 05:58am | #9

        I don't know - did I say that? I don't recall - but if I did, I'm sure it must be true, eh?Not 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        1. HocombContracting | Dec 13, 2006 06:19am | #10

          I think that icynene is open celled and does not hold water, is this correct.  In that case the moisture is not trapped.

          1. Piffin | Dec 13, 2006 06:32am | #12

            There are several reports in threads here at BT of open celled icynene becomming soggy with water whether from condensation or from leaks of one kind or anyother. I haven't seen it myself, but have no reason to doubt what was reported.With any open insulation, whether FG batts, chopped FG, celluloase, icy or other, when it gets wet, it is wet, and the lumber around it stays wet as long as the insulation does. It is common to see and to heara of rot and mold in connection with weet insulation. I've never seen any that dried quickly or at all once it was wetted.On one I was doing 2-3 years ago, there was a leak when the roofer was not punctual. I cut open the SR, replaced the insulation and patched the SR after drying the wood.
            Why? To get it out. The customers did not deserve a moldy house. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          2. User avater
            Luka | Dec 13, 2006 06:48am | #14

            Weet ?All these insulations...Fiberglass, cellulose, icynene, (oh my !)...And now you gotta introduce a new one called weet...;o)

            Get over it....... The angry going eat you up. ~Brownbagg '06

        2. Hackinatit | Dec 13, 2006 06:25am | #11

          I musta misunderstood this;

          "but how does the water get there in the first place, and become trapped? bad design ?"

          ApologiesTroy Sprout

          Socialism in general has a record of failure so blatant that only an intellectual could ignore or evade it."-- Thomas Sowell

          1. Piffin | Dec 13, 2006 06:37am | #13

            Yeah, I was just asking an open question, because the OP did not want to elaborate. Hard to know cases without specifics. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        3. DoRight | Dec 13, 2006 11:06pm | #15

          Exactly!

  2. MAsprayfoam | Dec 11, 2006 06:17am | #2

    Let me guess, these self-proclaimed experts heard of a case in the next county from their cousin who is married to the building inspector there!

    Sounds like the old urban myth working here against your good judgement. You are correct and those guys are scared to change and or think for themselves. I'm a mechanical engineer who started his own spray foam company a couple years ago. I now use Icynene and have no problems and know of none. When used properly in a normal conditioned space application I would not worry. It's many times safer than FG, that's for sure!

    Stu

    1. fall50 | Dec 11, 2006 10:44pm | #3

      I would like to hear one just 1 reason. 

      1. User avater
        CapnMac | Dec 12, 2006 01:37am | #4

        would like to hear one just 1 reason

        Please tell me you meant that tongue-in-cheek as in only one reason (not the 40-50 that could be "dog-piled" together?

        For OP's stated use, rims and cantilevers--spaces not only traditionally hard to insulate well, but under-observed ove rbuilding life-cycles, a nice, solid-filling, relatively impervious foam makes excellent sense.

        Ok, so many of those same arguments can also be used "against," too.  By completely filling bays, spaces, there's no way for water or water vapor to escape.  That means that any that exists, remains "in contact" with whatever it touches.

        But, that's only true, if, as previously posted, water or water vapor gets to the space in the first place.

        One, just one reason, to use foam, then--Since it fills the voids completely, there's significantly less space for water vapor to condense out ant become liquid water where it can damage the structure.Occupational hazard of my occupation not being around (sorry Bubba)

        1. User avater
          rjw | Dec 12, 2006 01:49am | #5

          >>One, just one reason, to use foam, then--Since it fills the voids completely, there's significantly less space for water vapor to condense out ant become liquid water where it can damage the structure.Is that true of all modern foams applied with reasonable skill?I see oly uffie foam installations which have noticably shrunk and pulled away from surfaces.

          The "War on Terrorism" has failed - in part by narrowing our options to only the option of last resort.

          I propose we start a worldwide Partnership Against Terror, in which the reasonable people of the world work together to oppose terrorism and the conditions which lead people to that desperate condition.

          "We hold these truths to be self-evident, that all people are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty and the pursuit of happiness."

          1. User avater
            CapnMac | Dec 12, 2006 02:14am | #6

            Is that true of all modern foams applied with reasonable skill?

            Well, that's a question to ask.

            Personally, for cantilevers, I'd be more inclined to use rigid sheets with low-epansion foam to seal them in--but I also, a bit cynically I admit, sort of expect that the only time a cantilever is going to get dug into is for either a remodel or a repair. 

            Across that sort of life cycle, I'd not expect fg to retain much value, and would need a really good "convincing" by the dense-pack celulose man.

            Reasonable skill, sometimes covers too large a ranger, perhaps?  Rim insulation has been some on my mind of late, as I keep seeing them sort of "skipped over" as "not my job."  So, I've been trying to come up with a way to describe a performance standard so that they are somebody's job, oand a job to do well--all while not necessarily precisely defining specific trade practice restrictively (or whatever the current gobble-de-gook, split-tongue, two-talker verbiage presently is . . . )Occupational hazard of my occupation not being around (sorry Bubba)

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