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How to fix poor blown-in cellulose installation?

lucyna99 | Posted in General Questions on

I’ve read couple of articles and watched video from National Fiber on your site, so I am now convinced that our blown-in cellulose installation is not of adequate quality. We have been pushing on the installers and they have come back 3 times by now, but I don’t think the job is finished. It is likely however that they will not come back. There is simply a different understanding between us of what would be the adequate job and what is not. After first install, it was enough to press on the netting couple of times in the center of the stud bay and the material would start coming tumbling down. We have subsequently rolled the stud bays using paint roller and broke 2 extension poles in the process (they took away metal roller seeing that it causes more trouble for them), insulation settled with voids of 2-8” on top of the bay, and they refilled these. They came back twice for this. But that is not the end of the story. Several more small gaps started to show after few weeks. We also felt around the electrical boxes and felt loose/soft insulation areas into which it was necessary to add insulation. We proceeded to stuff blow-in fiberglass chunks in those areas by hand.
When one cuts a hole at any place in the bay netting, e.g., on top, and one pushes down on the insulation, one can rather easily cause settling of 1 foot or more. We have proceeded to do this, and again, fill the resulting void with chunks of blow-in fiberglass. Fiberglass is very compressed, certainly not like it would have been if it was blown into those areas.
Is this method of fixing the poor job improving the situation? Is it OK to have the fiberglass compressed? How hard should we try to push on the cellulose to settle? I could see that if we did it from the top and in the middle of the stud bay we might reach the desired “firm mattress” that might not move after touching/pushing on it afterwards.

We have, of course, tried to require proper installation, but (1) we did not know exactly from the beginning what to demand (2) the relationship has become very strained, given that they had to come back multiple times already. The GC is of no help here.

We also tried to reason with them based on the expected bag count for the job. They said they installed 52 bags, 61 would have been the expected count, based on But did they really install 52 bags?

Our wall is 2×8 24 o.c. or 2×6 24 o.c.

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  1. lucyna99 | | #1

    The photos were attached rotated, just fyi. The drywall installation already started. We do have R-18 on the exterior wall hence will not be stranded without insulation if it settles in some places. But we would like to improve on the current status and seek the advice how to do it best.

  2. GBA Editor
    Martin Holladay | | #2

    You need to contact an insulation contractor who is experienced at dense-packing.

    Where are you located?

  3. lucyna99 | | #3

    Martin, we are in Pittsburgh. We have "fixed" more than 50% of the bays by our method, top only though. I don't know if we have time/a chance for working with another insulation contractor. The GC believes that the insulators he hired already attended to our requests for improvements sufficiently...

  4. charlie_sullivan | | #4

    I agree with Martin the that ideal is to get a skilled insulation contractor ... unfortunately that is harder than it sounds. I do think what you are doing is helping--easier to do it now than once the drywall is all up. You are lucky that you have R-18 on the outside, so you can consider the work you are doing as improving the situation, rather than avoiding a disaster.

    Note that the FTC has very specific rules about what kind of documentation insulators have to provide, and that your GC has to provide you if you are paying him for the insulation job. If it might be helpful to lean on those rules in trying to negotiate with those two parties, here's a summary of the rules; see item 3 on p. 3 for example.

  5. exeric | | #5

    Lucyna, it's very unfortunate your insulation contractor is so lackadaisical. It's apparent to me having done the dense packing job myself as a DIYer that the job is substandard. You should never be able to hand compress the cellulose so much that the slightest disturbance causes it to collapse. That is not acceptable work.

    Unfortunately, this kind of work done by people who don't know how to do the job right, or don't care enough to do the job right, is all too common. It sounds like the situation has soured and they might not be willing to do the job right. If that turns out to be the case the next best thing to do, besides getting a cellulose contractor who does good work, is to document all that you can about the poor workmanship so you can get legal remedy. That even includes references to this forum site to show the proper technique in cellulose dense packing.
    It really is a sad situation that someone like myself who did dense packing only once, using a rental blower no less, could do a seemingly far superior job of dense packing than these folk did. They should hang their head in complete humiliation.

    My best wishes to your household.

  6. BobHr | | #6

    are they not required to tell you how many bags of insulation was used. You could easily compute the density if you know the number of bags. From there I would make my case with the builder to get the contractor back out or get a new one at his expense.

  7. lucyna99 | | #7

    Hi Robert,
    We did that and determined that they were 9 bags short for each side of the duplex. 18 bags total, assuming the insulators told us true number of bags used. When they came back to refill voids they probably used up somewhere between 6-10 bags more, but the actual count was not given to us. Our GC hired them (they always work together) and apparently we've made many more demands for filling voids that they ever experienced. 24 o.c. wall can also make a difference here, based on the video from National Fiber found at this site. The density of cellulose may need to be a notch higher than 4 lb/cf when the wall is 24 o.c. to allow it to be supported laterally against gravity. This was not specified explicitly. Our GC has never built 24 o.c. in the whole 29-years of building career. And nobody is familiar with trying to reach Passive House standard and making walls of R42 in PA. So, we have to understand our whole debacle in that context... If we knew early on to ask to redo the blowing with the rigid hose everywhere (bottom, center, top), and about the possibility to set the density on the blower to reach 4 lb/cf maybe it would have been fixed by now...

  8. exeric | | #8

    I probably sounded ridiculously overconfident but that's not where my angst over hearing your story came from. When I filled in my walls, which were not close to Passivehaus levels, (2x6, 16" oc) I ended up having up to 5 or 6 holes where the hose went in on one 2x6 void. The reason I had to put so many holes for pumping cellulose is because I didn't know what I was doing. And I knew I didn't know what I was doing because it was my first time. I compensated. And it turned out well after rolling it with an aluminum roller.

    In a sense they were in exactly the same situation I was in that they had never done it in a situation like yours even though they have mucho experience. What bothers me is that so many people just sleep walk through construction problems. When something is different from what they're used to, like your situation was, they make excuses instead of adapting.

    It just drives me crazy when something "new" isn't registered and people use that as an excuse instead of adapting. Don't except their excuses for trying to coast through their work life. It's their responsibility, not your family's.

  9. stuccofirst | | #9

    you have to weigh samples to see if it is the proper lbs. per sq. inch.

  10. GBA Editor
    Martin Holladay | | #10

    The units for density are weight (or, more properly, mass) per unit of volume -- usually per cubic foot.

    Not per square inch or per square foot, which are units that measure area.

  11. stuccofirst | | #11

    Samples should be taken and weighed to see if the installation meets the recommended dense pack density of 3.5 lbs. per cubic foot or (preferably) greater.

  12. exeric | | #12

    Shane, I think you may be taking an overly literal approach that is just not practical. In practice even a beginner quickly gets the feel for what is adequately dense and what is not. When I did my walls I later calculated the volume of the walls and the bags of cellulose used and it turned out to be just over 3 and 1/2 lbs per cubic feet. If one is just the "least" bit conscientious even a rank beginner will know just by pushing on different areas those places that are underfilled. Have you actually done dense packing?! Of course the calibrated "feel" of the walls will have to adjusted by the depth and o.c. width of the framing. That also is quickly assessed with no need for samples taken, even by beginners. I admit to being very intuitive about these things. Some people have a mild form of autism (Asberger's Syndrome) with regard to developing this natural intuition.

  13. lucyna99 | | #13

    Hello Eric,
    In my effort to fix this installation, I compress the cellulose pressing from several horizontal cut points within the stud bay and fill these voids with blow-in fiberglass. I am usually able to create 2-3 feet of voids this way on a 9' bay. Is it possible that I compress the cellulose too much? To touch it does feel like a firm mattress and that I cannot compact it anymore with hand.

  14. exeric | | #14

    It sounds to me like you've developed the "feel". I understand exactly where you're coming from. It is hard to trust yourself when someone who says they've done it for years acts like you're coming from left field. It is a bit inexplicable to me that your insulation guy wouldn't see what you're seeing. At this point if I were you I'd trust your senses and that they have shorted you in density, for whatever reason.
    I can't imagine that there is any way you would be able to get 2 or 3 feet of open volume with hand pressure in a downward direction if there was adequate cellulose density. Good Luck!

  15. exeric | | #15

    Lucyna, something to be aware of: My understanding is that regular fiberglass batts are not meant to be over compressed because it loses its insulation value then when those air pockets are eliminated. This is different from the blown in blanket type of fiberglass fibers. If at all possible it is far better to have an insulation material that is meant to be blown in. What this would mean is that even though it is not ideal it might be better to get bags of cellulose and hand stuff it over hand stuffing fiberglass batts. I'm hesitant to mention this because I'm sure this is already a stressful situation for your family.
    Perhaps someone else can chime in here. I'm sure what you are doing will work, but it is not ideal and it is better to know that now than after your drywall is up if you decide that this is important to you.

  16. lucyna99 | | #16

    Hi Eric,
    Indeed, we were told the same by our PHIUS+/Resnet rater, and removed fiberglass batts from a few spots where the insulator stuck them in to cover the gaps. We only use the blow-in fiberglass to fill the voids created when we compress the cellulose to higher density. Based on the information on the Green Fiber cellulose 30 lb bags, they provide for the maximum coverage for 24 o.c. 2x6 wall at 19.9 sf. In their calculation, Green Fiber assumes installed dry dense pack density at 3.5 lb/cf. In the video from National Fiber, they say the density should be 4 lb/cf or a bit more for 24 o.c. walls. Which of these numbers should one use to predict the count of bags? The difference would be some 20 bags more with 4 lb/cf (bag count changes from 138 to 158). That's a lot. Our blue prints specified "dense pack" but not the density... And here is how our walls look after compression and filling the voids with fiberglass (some gaps by hand, some with the DIY blower). Two big walls still to go...

  17. ranson | | #17

    The green fiber installation instructions for 2x4 and 2x6 walls with 16in spacing say," Any cavity taller than eight feet in height should have cross-bracing or fire stops at mid-height to help support the weight of the material and prevent settling." That's pretty much stating that they would expect their 3.5pcf minimum to settle in a 9' tall cavity, let alone one made from 2x8 at 24" oc. 3.5pcf probably isn't a good standard for your walls.


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