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I've purchased a few bags of loose fill cellulose insulation from the local hardware store (GreenFiber brand). How will the insulation work if I don't put it through the machine to fluff it and force it through a tube? Will the insulation be compressed a bit so that I won't get the coverage that the bag says, but its R value per inch should be about the same? Can I consider its R-value to be something close to the "dense-pack" R-value?

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You can rent those blowers. Big box hardware stores usually make them available for installations. – The Evil Greebo Sep 27 '12 at 10:21
builditsolar.com/References/DensityvsRValue.htm shows a plot of the insulation value versus density. The density when I buy it is around 10 lb/ft^3, so that's off the chart... Also, is cellulose the same as cellulosic? It looks like it has a much worse U than all of the other insulators at the densities plotted.... – Pigrew Sep 27 '12 at 17:15
Following the plot, I'd guess that cellulose has R=2.5/in at 10 lb/ft^3, but it might go non-parabolic.... – Pigrew Sep 27 '12 at 17:44
I added more insulation to my attic a few years ago. From what I remember, HD will give you a free 24 hour blower rental with the purchase of 20 bags, and Lowes gives a free rental with 40. – Doresoom Dec 10 '14 at 15:12
up vote 4 down vote accepted

Since cellulose insulation is compressively packaged you cannot install it without using a blowing machine. I do not recommend trying to do this by hand. "A few bags" may not qualify you for loan of a machine, but you can certainly rent one from a big box home center or an equiment rental service.

The R-factor of fiber insulation follows an inverse "U" curve. As density increases, R-factor increases--up to a point. Dense packed cellulose insulation at 3.0 to 3.5 pcf--typical installed density in closed cavities--has an R-factor of 3.9 or 4.0, compared with 3.7 or 3.8 at settled density. Fiber glass at 2.2 to 2.5 pcf may have an R-factor in excess of 4.0, compared with 2.2 to 3.1 at design density. At some point the curves for both materials turn around and R-factor decreases with greater density. For cellulose that seems to be somewhere between 3.5 and 4.0.

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That type of insulation comes highly compressed, blowing it in will get separated and back to its original size. Without decompressing it the insulation won't have any air space, so less insulation value. You will end up using more insulation material and spending more money for less insulation capability.

Additionally without a blower you'll have trouble getting it actually dispersed into your wall in the first place. Blowing it in will get it spread out evenly, simply pouring it in will likely leave large gaps, meaning less actual insulating.

Next you have the time factor. blowing it in is quick, but if you do it manually it's going to take much longer. First you'll have to find a way to decompress it fully, then lift it up to the hole, then push it in the hole, then manually disperse it somehow.

So can you do it without blowing it in? Yes, but it will take much longer to do, cost more in insulation, and not be as effective in insulating your home, meaning more money lost over time.

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To @pigrew Cannot emphasize enough - DENSE PACK is bad for insulation. The R value on cellulose is its fluffy, properly installed value. Dense insulation is called "useless" (unless its foam) – The Evil Greebo Sep 27 '12 at 10:22

Having just done this, I'll report: doable, but a huge PITA. In order to get a good "fluff" on it, I ground it through expanded metal mesh (having tried a few other things which did not work as well first) - it's time consuming and dusty, but certainly possible if all you have to do is a bag/block or two. I've done one block, I might do another just to check the quality of a different supplier before placing a large order.

In my case it was a deliberate experiment, and the result of the experiment is that I will rent a blower ($70/day at the local rental place) and blow in (actually, I'll check against the cost of "having it done," as well); also that I won't be buying HD's "cellulose", which had a significant amount of plastic scrap in it (one does get up close and personal with the insulation when hand-grinding it through a sheet of expanded metal mesh.)

Methodology was to pry out a chunk of compressed insulation, place it on the expanded metal (an old patio table, in this case) and use a block (or your hand, but the block is more efficient and does not mind grinding on metal) to work the insulation though the mesh - then shovel/sweep to where it's needed (open attic application, not wall-stuffing.) A better setup could be made by building a box with sides and a mesh bottom to work it through, but it's not enough better to beat just using the right equipment on a larger-scale job. Certainly possible to do, however, if you have the time and patience and a dust mask - when what needs doing is small, and the rental of a machine exceeds the cost of the insulation.

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I did an area above a garage using a mud (drywall) mixer on a drill and bent wire to fluff it up. For the few bales that I used, it worked well. I used a leaf rake to level it out. On flat ceilings with room to work it would be OK.

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Cellulose insulation is available in batt form (like fiberglass batting,as rolled blankets, with or without vapor barrier). If you don't want to rent a blower, or if you're insulating open walls or ceilings, this may be an alternative. It will probably be more expensive to achieve the same R-value this way.

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I had done this manually in my walls . I stapled down a roll out tarp paper to each stud and the bottom stud. Did this half way fluffed it in a huge crawfish pot(I'm from Louisiana), and used a dust pan to scoop Nd fill between each stud. Went back on the top tucked it into the lower trap stapled down and did the same as filling. I also note I'm doing this in a tiny home. 300 sq foot ground.

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