DIY Blown Cellulose Insulation – 90% Less Expensive?
AdamT
| Posted in General Questions on
I’m comparing the cost of mineral wool batts to blown cellulose and am getting an unexpected result:
For an R40 application I estimate $11 per sf for mineral wool batts and about $1 per sf for blown cellulose (also R40). For a 3,200 sf application, this comes to a $33K difference! ($36K for the batts, $3K for the cellulose).
Why not buy a $5K t0 $7K blowing machine (capable of dense packing cellulose), hire someone to help for a week or two and save $25K?
Is my math correct?
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Looks a bit off, R38 of mineral wool works out to about $5/sqft at the box store, less from building supply. Still WAY more expensive than cellulose but not enough to justify buying a machine. Dense packing thick walls is hard, I'm not sure if one week DIY time is realistic. High density fiberglass is about 1/2 the cost of mineral wool and it is really the best option for a simple budget install.
I think what we need is a good way to loose fill walls with cellulose. This way you can get the blower machine from the box store and insulate both walls and attic in one shot.
What we really need is widespread availability of densepack-capable rental blowers.
Exactly. The single stage blower that came 'free' with my insulation purchase from a box store was not only beat up and poorly maintained, but prob. couldn't have done a good job brand new. The two-stage Krendl blower I rented from my local independent building supply store worked great, and was much cheaper than the box store blower. I have no doubt the box store blower works for someone doing a *small* amount of loose fill. If I had relied on it to do my attic, it likely would have taken two or three days, 1 or 2 of which would have been paid rental at the inflated rate of $150/day.
Surprisingly (to me), fiberglass was NOT the best option for my very DIY build. It turns out that hiring an insulation crew to wet spray cellulose into my walls was actually LESS EXPENSIVE than the option of me buying fiberglass batts from a supply house and then installing them myself (zero labor cost).
The fact that cellulose would be cheaper than the raw material cost of fiberglass even when adding in a labor cost plus profit just blew me away.
Plus, I'm a big fan of cellulose and would prefer it over fiberglass in nearly any circumstances so it was win-win all around.
Hi Adam,
When I did some cost comparisons (material cost only) I used $/R-BF as a basis for comparison. Here's my results for some common insulation materials:
Product_____________R/inch (25°)___$/BF___$/R-BF
Insulfoam EPS Type 1__4.35_________$0.23___$0.05
Sopra 30 XPS________ 5____________$0.54___$0.11
Dense pack cellulose__3.8___________$0.12___$0.03
Mineral Wool_________4.2__________$0.42___$0.10
Fiberglass Batt_______ 3.8__________$0.19____$0.05
There may be something off with your math. R for R, cellulose is certainly cheaper than mineral wool, but not by a factor of ten.
FWIW, I went with dense pack cellulose and installed it myself, using a rental machine.
—David
Product___Cost/board_foot___R-Value/inch___Cost/Rvalue
Wool_batt___$0.41___3.6___$0.11
Polyiso___$0.58___6.5___$0.09
Rockwool_batt___$0.23___4.1___$0.06
Fiberglass_batt___$0.11___3.5___$0.03
Rockwool_board___$0.81___4___$0.20
Cork___$2.10___4___$0.53
XPS___$0.47___5___$0.09
EPS___$0.39___3.9___$0.10
HFC_Closed_cell_Spray_Foam___$1.00___6___$0.17
HFO_Closed_Cell_Spray_Foam___$1.50___6.3___$0.24
Open_cell_spray_foam___$0.50___3.6___$0.14
Dense_pack_cellulose___$0.10___3.8___$0.03
Blown_wool___$0.50___4.3___$0.12
Pour_in_cork___$0.94___3.9___$0.24
hempwool_2___$0.55___3.7___$0.15
hempwool_3.5___$0.39___3.7___$0.10
hempwool_5.5___$0.35___3.7___$0.10
(Stealing your idea of using underscores for formatting)
I'd love to see damp applied cellulose added to this list!
Thanks David and Akos,
This turns out to be an embarrassing way to introduce myself to the community. Indeed, there are more batts/package than I understood and my #'s are way off.
David, is BF board foot above?
Yes, board foot. 12” x 12” x 1”. I dense packed 2x6 24” OC stud bays at 3.5# LF, or about 1 25# bag per bay.
A few more details, if you're still planning to dense pack yourself:
For the difference in cost between dense pack cellulose and mineral wool, you probably can't afford to *buy* an insulation blower, but in my area, the Krendl 425 I used rents for $45/day. Probably have another $25-50 in parts to set it up for dense packing. Including stapling and gluing webbing, and the learning curve on dense packing, I was able to pack about 400 SF/day, using a helper about half the time (it's much faster with a helper). If you have full time help, you could probably do your whole 3200 SF in about 5 days, esp. if you staple and glue all the webbing before you rent the blower (I planned more poorly, and only had about 1/3 of the webbing done before I started blowing).
So, maybe $250 for blower rent, and another $50 to rig the reducer and packing hose. $3-4K in materials. If you don't have to pay a helper (my wife worked for free), and if you don't count the value of labor for either of you, DIY dense pack likely saves you $2500-$3500, versus mineral wool.
Not the crazy savings your initial #s led you to believe, but not nothing either.
Plus, the carbon footprint of cellulose is quite a bit lower than mineral wool. Arguably, cellulose is even better than carbon neutral and sequesters carbon.
Still, DIY dense packing is a messy business (see attached pic).
Thanks Drake! That's good info. As you can tell, I'm new to this business but love the idea of figuring it out.
Great photo too!
In NJ, I couldn't find anyone that had experience dense packing new construction. Therefore, my choices were fiberglass, open cell, and mineral wool.
Mineral wool almost forces a good install, but it was basically twice the price of fiberglass. Open cell was decidedly in the middle of the two, and I went with it. I'm happy with that choice, all things considered.
It is not hard at all to do a DIY cellulose dense pack job. The only limitation is that if you rent a lower power big box machine it must have a slide gate to keep it from bogging down. The slide gate Intec Cyclone at the orange box store will work. It only produces about 3.2 lbs/cubic ft so you can't blow cellulose through holes drilled into drywall if you don't want it to settle and create a gap at the top over time. It requires blowing cellulose through insulweb backing. When you use a roller to flatten the bellying out that's produced it brings it up to the required 3.5 lbs/ cubic ft that is necessary to stop any settling. You are using human power to bring the density up to what's required. I would not attempt DIY on any wall thicker than 6" though. Here are some threads where I mentioned doing my own DIY cellulose job. It seems like ages ago.
https://www.greenbuildingadvisor.com/question/bibs-fiberglass-dense-pack-vs-cellulose-dense-pack.
https://www.greenbuildingadvisor.com/question/dense-pack-cellulose-rig-rental-in-philadelphia-area
https://www.greenbuildingadvisor.com/question/dense-packing-cellulose-in-a-wider-wall-with-a-low-powered-blowing-machine
https://www.greenbuildingadvisor.com/question/dense-packed-cellulose-insulation-settling-and-support
Exeric,
Thanks for all those earlier posts—they were extremely helpful, not only giving me confidence to try my own DIY dense packing, but tons of information I couldn't have done without. Still can't imagine doing it with one of the blowers from the orange box store, though, esp. after using a two-stage machine.
Thanks again,
David
Exeric - thanks for listing those posts. I caught a few of them earlier on this site and have gone back to them as I figure this out.
Thanks Drake and Adam. Contributing to this community is its own reward but I still appreciate the recognition. I sometimes feel like I'm sending a message in a bottle on the high seas and not knowing if it ever landed. It's great to hear it did.
Yeah, I found the bottle. I had already copy-pasted some of your comments in a running word doc that I have on my computer. Keep up the posts!
exeric,
When your bottles wash up on the shore near me I find the contents useful and informative.
Sorry to hijack this thread, but I believe this is relevant.
I'm planning to DIY my own dense-pack cellulose on a 12" double stud wall. Can someone explain why this is a bad idea?
I'm planning to isolate the stud bays with strips of insulweb, and this should eliminate what I understand to be the biggest pitfall to achieving proper density - the undesirable flow of cellulose between stud bays keeping you from achieving proper density.
In my mind I'm picturing a deeper cavity (once isolated) actually being easier to properly fill since there will be much more space to manipulate the pipe within the cavity.
Thoughts?
It's going to be a lot of work to install insulweb to partition off all the stud bays from each other. Aside from all that extra labor, I see no reason why your plan wouldn't work.
Bill
Thanks Bill. It’s a good thing I work cheap!
I concur with Bill. Lance's idea doesn't really deviate from the 6" thick layer rule for DIY. It's just doing two 6" layers back to back. It's just going to be extra labor though.
Here's an idea/brainstorm:
Use a low power blower to partially fill a cavity then manually compress the material to the desired density. Refill the cavity with material and manually compress it again. Repeat until you get to the top. This would probably work for the lower portion of a stud column. You could then install batts at the top that won't settle.
Looks like I just found a rental unit in my area capable of commercial dense packing. I'll be DIY'ing it the right way.
Nice! Let us know how it turns out and what you learned along the way!
You can also modify an electric leaf blower. I blew in cellulose in all my wall cavities with one. Saved a fortune with my setup.
Uh, how do you feed insulation into a leaf blower?
I used a large metal trash can and a paddle mixer on a drill to break up the cellulose first. I did my entire house with it and it had excellent results.
https://www.youtube.com/watch?v=zS5UyEI3HCM
That looks really slow. I'm not sure it wouldn't be faster just to crumple the insulation and place it in the hole by hand.
DC,
Yeah, but maybe you can make the time up by simply covering the holes in the drywall with blue tape and moving on.
That's built into my time calculation already.
With my setup I can empty a whole trash can and fill an entire 8 foot wall stud bay in like 30 seconds. The video posted does seem very slow. I use the large black intake tube on my blower to directly suck up the already fluffed cellulose from the trash can. The leaf blower also shreds the cellulose again. The leaf blower actually has too much power on high and will blow the sheet rock off the wall if your not careful. It happened to me on a section of wall in my garage where I first experimented with the blower.
Patching the holes is super easy with a 4 inch hole saw. You just put the round sheet rock piece back in the hole with some wood and skim it.
I am using this black and decker leaf blower from Home Depot in the screen shot below. I simply disconnected the 4 inch black flexible tube from the bag and insert it into the wall.
BLACK+DECKER
12 AMP 250 MPH 400 CFM Corded Electric 3-In-1 Backpack Leaf Blower, Vacuum & Mulcher
I watched the video and there are some problems with it. I understand the reason to do things on the cheap but when you do that one needs to understand the issues involved that makes specialized equipment necessary. I noticed that the person didn't snake the hose into each stud bay. It would be impossible to get the stud bay to sufficient density if you were using cellulose using that method. I have my doubts that it would even work with fiberglass but I'll reserve judgement on that.
If you used that method with cellulose all that would happen is that local density right at the hole would increase but there would be huge areas moving out from the hole with low density of cellulose. That's just because of friction to movement of cellulose. Cellulose would pile up at the hole and give you the appearance of the stud bay being filled with a simultaneous sound change as the local density increase at the hole stops the flow of cellulose farther out from the hole. I suspect the same thing would happen with fiberglass.
The Krendl blower that ddrake references above is rated at 14 amps continuous, or about 2.25 HP. To get that power level it cleverly has a two-stage blower and you have to plug it into two outlets on different circuit breakers.
The AttiCat that Home Depot rents is rated at 0.75 HP. Handheld leaf blowers are going to be even less. In order to deliver the flow and pressure needed for dense pack you just need a lot of power.
Now there are gas powered handheld and backpack leaf blowers that are in the 2+ HP range. You could perhaps use one of them as the basis of a DIY blower. You'd have to make a hopper and figure out a way to blow air through the hopper and out the hose without just blowing the insulation back at the operator.
If it were me I'd start with a 240V 2hp motor and a dryer plug.
When I did research for my blow I found out the AttiCat was only for non- dense packing of fiberglass in attics.
Posters here have found that they if they throttle down the flow they can get the pressures necessary for dense packing. It's just slow going.
Yes, but the way of doing that is through the use of a slide gate, which changes the ratio of air/cellulose without changing the power output. You can't just throttle down without also lowering the power. The AttiCat doesn't have that feature and the Cyclone does.
Also, the whole reason for using the Cyclone was because there weren't any other halfway suitable blowers in my area. I was able to make it work and get the density I needed for dense packing with the use of the "gearing" that its slide gate allowed. If you have the option of renting a two stage by all means use that option. If you don't then an Intec Cyclone available at Home Depot will work. An AttiCat will never work for dense packing.