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Community and Q&A

How many cubic feet in one bag of cellulose insulation?

Dave Cummings | Posted in General Questions on

My situation is unique where I need to fill many large angular voids in my wall cavity. All the calculation charts I have seen use R-value and Square foot parameters. I called the manufacturer however the man I needed to speak with is on vacation. Harumph.

Does anyone know how many cubic feet (on average) is within one bag of GreenFiber Cellulose insulation? I need to fill about 425 cu ft. Thanks!

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  1. Expert Member
    Dana Dorsett | | #1

    At open blow densities you're looking about 1.3-1.5lb per cubic foot, but in a decently done 2-hole method wall cavity density will be 2 -2.5lbs/ft, not more unless you dense pack it. Dense pack starts at 2.8-3lbs and single stage rental blowers rarely deliver higher than 3.5lbs density, and then only if you have the necessary dense-packing hoses and know what you're doing. IIRC GreenFiber has traditionally been sold in 25lb bags, though at box stores I've seen it in 19lb bags recently, so figure on about 10-11 cubic feet per 25lb bag, 7.5 - 8.5 cubic feet per 19lb bag if blowing it 2-hole method.

    At any bag size you're looking at about 1000 lbs to fill 425cubic feet. An experienced dense-packer can probably stuff 1400-1500 lbs in there with a single-stage blower, 1600-1700lbs with a 2-stage.

  2. Dave Cummings | | #2

    Thanks Dana. I knew someone out there would have the answer!

  3. Chris Brown | | #3

    Dave, blown fiberglass would also do the trick while requiring less than half the bags of cellulose (especially if you can only find the smaller big box bags). In cavities like you describe, installed at 2.2 lbs/cu ft, it actually provides better air resistance than does cellulose. JM, Knauf and third party testing agencies have done some excellant work in this area.

  4. GBA Editor
    Martin Holladay | | #4

    Note to GBA readers: To the best of my knowledge, Chris Brown is the business development manager at a well-known manufacturer of fiberglass insulation, Knauf Insulation.

  5. Chris Brown | | #5

    You are correct, my oversight. When typically posting issues related to insul or air sealing, I have identified myself previously. Oh well, at least I didn't just toot our own horn!

  6. Expert Member
    Dana Dorsett | | #6

    Just curious, but is 2.2lb fiberglass (or 1.8lbs) even remotely a DIY proposition?

  7. Chris Brown | | #7

    The process itself is essentially equal to installing cellulose. Using a system like Owens Corning's Attic Cat system, or any other fiberglass manufacturer's blowing wool product with an appropriate blowing machine and hoses works just fine. If one understands how to install cellulose in closed cavities, then fiberglass will not be an issue. The only real variable is the material itself.

  8. Expert Member
    Dana Dorsett | | #8

    It's pretty springy stuff I'd expect to need a 2-stage blower to actually hit 2.2lbs with fiberglass. Most of box-stores that rent any blowers at all usually only have the low end Force-1s, and the condition of the hoses are sometimes questionable (the REAL use for duct tape, I s'pose). I've never seen any who had dense packing tubes as part of the rental package.

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