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Cellulose corrodes metal?

hurnik | Posted in Energy, Heating & Insulation on August 16, 2006 03:46am

I’m not sure someone wasn’t yanking my chain, but the HVAC guys that installed my new furnace/AC told me that I couldn’t have my house dense-packed with cellulose because it corrodes the metal and the ducting, etc. would all be rusted.

???

I know that cellulose is treated with boric acid, and some dense packs are a “wet” application, but this is the first I’ve heard of it rusting and corroding metal.

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  1. Piffin | Aug 16, 2006 05:16am | #1

    More likely the opposite, if you have any situation where condensation can form at thjose metal items.

    There are situations where moisture can be trapped in cells, but that indicates another problem someplace in the house with excess water getting to it.

     

     

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      BillHartmann | Aug 16, 2006 06:59am | #3

      There is some truth to that.Some years ago some was produced with another chemical and it caused corrosion problems.Here is the story. But it does no indicate what the checmical was or when this happened.Here is the current situation.http://www.cocooninsulation.com/Corrosion.asp?Type=L"There have always been concerns about insulation causing corrosion when in direct contact with metal building components such as sweaty pipes, electrical wires or metal boxes, etc. Consequently, ASTM standards for every insulation material contain testing which specifically addresses these concerns. In addition, in 1979, the CPSC promulgated a law, which regulated the fire and corrosive characteristics of cellulose insulation. A statement of compliance with these requirements is required on every bag of cellulose insulation. The types of metal tested with all insulation materials are copper, aluminum, steel, and additionally in Canada, galvanized steel. Our test requires placing soaking-wet cellulose insulation with an imbedded .003-inch thick metal coupon inside a humidity chamber under conditions that are ideal for promoting corrosion. After 14 days, the metal coupons are removed, cleaned, and examined under a light to detect the smallest pinhole. In all, there are two coupons of each metal and all must be free of even one pinhole. This is a very strict test!"

      1. hurnik | Aug 17, 2006 12:11am | #4

        Thanks everyone. I contacted the "regular" cellulose guy and he said that yes, it *can* corrode, but only if using cellulose treated with amonium something or other (as opposed to a borate cellulose).ORIf the cellulose gets wet and stays wet for a long time. My thought on the AC condensation was that if it could "sweat" with cellulose around it, it could surely sweat with that flex "insulation" around it too, so that's why I thought they were pulling my leg.The place that said this, BTW, LOVES to foam (I've got nothing against foaming except that it's about 3x the price of cellulose around here, and our town won't let you use it on the roof deck).

      2. User avater
        BillHartmann | Aug 17, 2006 02:15am | #5

        I see that I forgot the link about the metal corrosion.http://www.chemaxx.com/cellulose.html

    2. rasconc | Aug 17, 2006 04:35am | #6

      I took down a couple of shelves  in DW's sewing room that I had installed with some galvanized deckscrews and wall anchors.  They had about 3/4" of light rusted area.  I being paranoid went out and removed a piece of the siding and took a hole saw and cut through the sheathing.  The cells seemed very dry and no evidence of any leaks.  I measured the plug and it was right at 3/4", can not remember for the life of me but think I sheathed with 3/4 osb because of the price I got at the time, about the same price as black board.

      I am sure that the barriers and wrap, etc is totally against the latest from the building science gurus. 

       

  2. caseyr | Aug 16, 2006 05:19am | #2

    I am not an expert in this area, but I have read quite a bit. The cellose folks and the fiberglass folks love to take pot shots at each other, using their own best case and comparing that to the worse case of their competitors, so I haven't seen any really valid comparisons of the two.

    However, it does appear that under some circumstances, metal brackets, fastneners, and other metal objects can be subject to corrosion. I have been unable to discern whether this is because the cellulose held moisture for long periods of time against the metal or whether the boric acid significantly accelerated the corrosion. I am guessing it was primarily a problem with moisture being held for long perids of time as a result of poor flashing and other building problems.

    The fiberglass folks love to throw out the corrosion from cellulose insulation, but I have not seen any citations from them. I am guessing that the corrosion does occur, but that it is not at all common and is probably primarily the fault of poor moisture control.

  3. joeh | Aug 17, 2006 05:25am | #7

    What a load of crap.

    How is the insulation going to get wet?

    If you have that big a water problem, rusted dusts are gonna be way down your list of problems.

    Joe H

    1. hurnik | Aug 17, 2006 05:31am | #8

      That's what I thought, but they tried to say that if you ran cool air (ie, Air conditioner) that it would condense moisture. I was like, "um, isn't the insulation supposed to prevent "hot moist" air from hitting the cold ductwork?I live in the north east and even my uninsulated section of the basement has NEVER had moisture on any of the ductwork

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