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DP cels blowing off the drywall!

| Posted in Energy, Heating & Insulation on May 8, 2002 09:05am

For the last few days I’ve been learning to dense pack cellulose. Bought the Cocoon cels from Lowes and they lent me the Cocoon blower. Greenstone (they make Cocoon) tells me the blower is really a Promax 118. I’ve mainly been blowing into a cathedral ceiling where the bays are 14.5″x9.5″x13.5′ long and I’ve calculated a density of 2.5lbs/cu.ft. It takes at least 20 min. to fill each bay.

My problem is that when I try to get more density by closing the gate down to about 2.5″ (which gets me about 3lbs./cu.ft.) I start to blow the drywall off. The drywall is screwed down well. I then tried a wall and got the same results; 2.5lbs. seems to be the max. I’ve seen people here talk about 3.5 -4lbs. density and I’m worried about future settling at only 2.5lbs.

What am I doing wrong?

Jerry

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  1. wflather | May 08, 2002 08:35pm | #1

    I expect that you are doing nothing wrong, except blowing to a higher density than the drywall installation can withstand.  I had a similar problem.  After the first time, as soon as I would hear the first pop, I would stop and screw on a 1x long enough to cover several stud bays and hold the drywall in place until I was done with those bays.  The drywall only popped off at the deepest penetration of the hose, once the cavity was filled and I started to slowly withdraw the hose, completing that bay I had no proplem.  Not every bay would do this.  Perhaps 3 lbs/ft2 is just too much, my understanding is that 2.5 lbs/ft2 is sufficient to prevent settling.

    1. User avater
      mmoogie | May 10, 2002 04:33am | #2

      How large of an opening are you using for how large of a hose? If there isn't enough breathing room around the hose you could be building up too much air pressure. I usually use about a four inch hole for a 2 1/2" hose and have never blown the drywall off. I wrap a rag around the hose at the hole and hold it loosely to keep the stuff from flying all over the place, but still allow air to blow back. Are you screwing your screws in too deep and breaking the paper face? are you using an 8" screw schedule?

      I've never been able to do better than about 3.5 lbs, and usually closer to 3. I've read that over 2 lbs will not settle. Denser than that is better to more effectively block air movement.

      Steve

      Edited 5/9/2002 9:35:09 PM ET by STEVENZERBY

      1. oldjerry | May 12, 2002 09:39am | #3

        Steve, Bill;

        Thanks for the replies. I've learned a couple of things over the last few day with you guys providing the hints I needed. Bill mentioned withdrawing the hose slowly and I noticed that the drywall would "pop" right after the first stall as I pulled back on the hose. You could actuall see the drywall suddenly flex outward  as the backpressure built up in the hose and machine was released into the wall cavity. I found that pulling back slowly, and preferably before the flow completely stopped I eliminated that large pulse of pressure and got even more density. (I'm getting around3#/cu.ft. now) I am working alone, so sometimes the machine would be stalled while I was busy, then I'd go over and yank on the hose and... pop. I rigged up a remote control for the blower and that helped too.

        Steve mentioned 8" OC screws and I had screwed at 12" OC (with screws set correctly) thinking I was doing a little better than the usual 16" OC in the field for walls. I went ahead and double screwed the field as I was blowing and between the extra screws and the improved technique the drywall stayed where it belonged. BTW, to answer your question I was using an 1-1/4" hose in a 2" hole with the rag, as I had read your suggestion in an old post. I also used your method to hang the drywall with a horizontal space; worked great!

        Thanks Again,Jerry

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