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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
  • Locally the machines cost $50/day. But I'm reroofing a 12 x 12 shed, doing the roof in 2 halves (To minimize the risk if it snows) So it would be two rentals, two trips to town (1 hour) and associated gas for the truck. I have the insulation left over from the house. So in my case, doing it by hand, even if it takes twice as much insulation is worth it. – Sherwood Botsford Jan 25 '17 at 18:04

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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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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.

  • Re: HD's cellulose: How much is significant? 5%? Why does it matter if it has small amounts of plastic. Mind you, it depends on what kind of plastic. PVC produces toxic gas in a fire, but PE is long chain wax in essence. – Sherwood Botsford Jan 25 '17 at 18:12
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    I don't have facilities to assess what sort of plastic contamination it was, nor did I try to evaluate the percentage. I found many pieces (dozens) in a single bale. Some of it appeared to be plastic strapping from bundled paper with was obviously tossed straight into the grinder rather than having the strapping removed - other stuff was less clear in origin. I bought and paid for a bale of cellulose insulation, not a bale of cellulose insulation and plastic scrap. The other supplier appeared to be able to meet that standard and was actually a hair cheaper, too. – Ecnerwal Jan 26 '17 at 0:11
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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.

  • Good idea. I'm going to try this, using half a plastic barrel for a mixing tub, and weaving some HT fence wire through the mud mixer bit. – Sherwood Botsford Jan 25 '17 at 18:06
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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.

  • 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
  • Actually, cellulose r-value varies very little with density. The primary reason for fluffing it is, as you said, to make it go further (and reduce weight). – isherwood Mar 8 at 19:26
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A large plastic trash can, an electric drill, and a paddle wheel paint stirrer sized for 5-gallon paint buckets works wonderfully and is actually quite fast. If you fill the trash can 1/3 full with chunks from the bag, you can actually see it grow in size as the paint stirrer does its work.

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Doing some small areas where i cant put fiberglass batts in the attic bays. Used a Shop-Vac after breaking the insulation into smaller chunks in a large bin. The Shop Vac seem to fluff it pretty good. the volume of the product increases substantially. From there i just empty it into the attic bays and compress it slightly. Seems ok.

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    Hello, and welcome to Home Improvement. I'm guessing you mean you suck the insulation into the ShopVac, and then when full dump it into the attic? Some details, and maybe even a picture, would be really helpful. Thanks. – Daniel Griscom Dec 19 '18 at 17:50
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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.

  • Batts make more sense for walls -- if the wall is open. I have twice now, run into batts in ceilings where there was a batt between truss chords, but nothing over the top of the chord. Since ceiling insulation is where the bulk of the heat loss occurs, getting it deep and getting complete coverage is important. Easy to do with loose fill, whether fibreglass or cellulose. – Sherwood Botsford Jan 25 '17 at 18:08
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Yes, you can do it manually in the attic. I do it all the time when you only have to do a couple of bags. What do you do with a bag of ice when is tight? You smash it to the floor or as if it was a piñata. Then you can use a rake to evenly distribute the cellulose insulation.

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    Hello, and welcome to Stack Exchange. Thanks for the answer, but going forward please keep your answers to-the-point; name-calling will just end up with your answers being deleted. – Daniel Griscom Mar 6 '18 at 2:52
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A hand-held kitchen mixer works even better than the paint stirrer. Just throw chunks of the unexpanded insulation into a 5 gallon bucket and whip it up.

Don't skip the dust mask, though.

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As many have said, insulation requires air pockets within the material to have any R value. Those pockets effectively trap temperate air and reduce thermal transfer on opposite sides of the material. So yes, it HAS to be fluffed from it's vac-packed shipping form to be of any use and this will also make the material go further.

My DIY method for fluffing and blowing without renting a machine - HD, for instance, rents the O-C Atticat for free with a 10 bag purchase - is to use a 50 gallon trash can and a 3 foot paint paddle on a drill just to stir the stuff up. Second, I blow it through the impeller on my leaf vac/blower. In the case of my garage where I was adding to the walls after the fact and didn't want to be doing a bunch of taping and mudding removing the drywall, I cut a 2" access hole near the top of the cavity and blew it through the leaf vac and a 2" hose attached to the blower nozzle end. IT WORKS.

  • I'd dispute your first sentence. Cellulose has immense porosity even when baled. The primary reason for fluffing it is, as you said, to make it go further (and reduce weight). – isherwood Mar 8 at 19:24
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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 and 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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