Soooo...thinking up a silly newbie non-builder idea I'm sure: What about not having to pay for dense pack cellulose and simply tight stack the cellulose cubes within the double stud wall, they're already super super dense (would guess higher r-value and sealing than best dense pack application) and already vapor sealed due to packaging? Then maybe on exterior studs install say 4" of seam taped foam to seal and loose spray (DIY) on interior cavity... Am I crazy? Any thoughts on what the r-value per inch is of a cellulose block? Thoughts are around labor savings, great r value, vapor barrior, etc..?

I don't think that's such a good idea. I'm prety sure the packs are at least twice the density you need (one installer told me around 10 lb/cubic ft) if not more so you'll have to buy more than twice as much material to save on labor. R value for cellulose starts to drop above 2.5-3 lb/cubic ft.

http://www.builditsolar.com/Projects/Conservation/Dense_Pack_Cellulose_Insulation.pdf

and I have no ideea what you might get at 8 or 10 lb/cubic ft but probably you'll be significantly lower in R value. without the blower action I doubt cellulose will get in all the areas and you'll probably end up small air pockets everywhere.

I was worried about the same problem and I decided so space my double wall in such a way that I could use Roxul bats (DIY) in case the dense pack quotes will be outrageous - vertical batt in exterior wall, horizontal batt in the middle and another vertical in the interior wall. not ideal but....

I'd say either do it properly of find another solution.

good luck,
Adrian

What Adrian said. As packaged for shipment & storage you'll be at 4x dense-pack density, and use 3-4x the material, cost as-much or more as having somebody show up with a decent blower and have- at it.

Also, keeping the material encased in plastic vapor barrier means that should it ever get wet it'll NEVER dry. Cellulose is hygroscopic- it can buffer a lot of seasonal (or even minor leakage) water without damage, as long as it has a means to dry.

Using poly vapor retarders on the interior of studwalls without providing a rainscreen gap under the siding (required by Canadiadian code, but not in the US) sometimes limits the drying capacity too much, causing the assembly to take on moisture over time (years even). Best-practices would be to keep the retardency above 0.5 perm on both the interior or exterior sides, and maximize exterior drying with back vented (rainscreened) siding wherever possible. (In very cold climates you may still need interior poly, but not in most of the US and the less-cold parts of Canada.) If the climate is such that the mean January temp at the exterior sheathing can be adjusted to 37-40F or higher by putting exterior foam insulation over the sheathing, skip the interior vapor retarder altogether and use standard latex paints (which will run 2-3 perms). That way the assembly is resilient to incidental air leakage from the interior, and has maximal drying capacity for other moisture intrusions. In VERY high R double-studwall or Larsen Truss types of assemblies, rainscreened exterior siding and either latex or vapor retardent latex primer (depending on climate) would work best.

Hi, I have been looking for a cellulose insulation supplier who might be interested in making just the sort of bloc you describe, and I think it's an excellent idea. I have some specific ideas on how this could be possible. My background is in residential construction, and the area I live in supports a very skilled and knowledgeable economy, which has an important ongoing positive impact on being able to follow new Ideas, and high standards in a competitive built environment. More recent information is available, and presently is being updated. google Monolith Biocrete Bioblock Even a good idea does not always become adopted for often unknown reasons, so I welcome the opportunity to share my own data and thus continue to learn. Bradley