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Dense pack cellulose alternative in wall stack up

dfvellone | Posted in General Questions on

There are no cellulose installers in my area willing to dense pack the open cavities of my 24 o.c. studwalls, which had been my original plan and preference. There is an installer that blows in fiberglass, and short of that working out I’d have to consider roxul batts. 

The wall assembly is comprised of full dimension 2″x5″ studs and the exterior is insulated with 2.5″ xps. I’m in climate zone 6. I will install Membrain after the insulation gets installed. I understand that 2.5″ of xps is barely sufficient for dew point control, so my question relates directly to the functionality of the insulation in this stack up given this factor.
Thanks, Daniel

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  1. Expert Member
    Michael Maines | | #1

    Daniel, with a variable permeance interior membrane you should be fine with blown fiberglass, as long as you have at least one good air control layer in your assembly. Siga Majrex and Pro Clima Intello have better performance numbers and are much more durable than Certainteed Membrane, but any of the three should work.

  2. Expert Member
    Dana Dorsett | | #2

    Denim batts have comparable hygric buffering characteristics to cellulose, and can be DIY installed, and can be sourced through box stores if you can't find a lower cost distributor.

    An R21 UltraTouch ™ designed for milled 2x6s would perform at about R19.5 or a hair more when compressed to 5.0" in your non-standard stud depth framing. The batts themselves are manufactured at a 23" nominal width, enough for a friction fit in the the standard 22.5" 2x6 24" o.c. stud bay without causing the batt to buckle. I suspect it would do just fine ( no buckling) at 22.0", but I've never tried it.

    Eventually (before 2050) most of the warmer half of Zone 6 will most likely be be in Zone 5, offering a bit of dew point margin, all thanks to global warming.

    1. oldbungalow | | #4

      paradoxically, global warming may also weaken the polar vortex, causing extreme cold snaps

  3. oldbungalow | | #3

    Speaking of UltraTouch, I asked in a related Q&A if anyone had experience with Ecocell Cellulose batts. I wonder if the two products are essentially the same, given that cotton is basically cellulose. I imagine the fire/mold treatment would be the same whether it's paper or cotton waste. Is Ultra Touch more resistant to air movement than fiberglass, and similar to blown-in cellulose?

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