[Greenbuilding] Cellulose

[Laren Corie]

From: "JAY WALSH" <jaywalsh at usa.net>

>  I see in your latest message that you are dealing with some large open
> bays, approx 8' x 10' x  9-1/4". Trying to dense pack this large cavity will
> be extremely difficult and there is a good chance you will get settling over
> the years.

Hi Jay;

  Just curious. Do you have any evidense of that, or are you just guessing?
Perhaps your line of logic runs differently than mine, but mine tells me that
if holes are drilled in the drywall (or exterior sheathing) on the same centers
as would be used with full depth studs, that there is nothing interfering with
the wall being filled to its capacity and pressure. As a matter of fact, there
is less interference than there is in a thinner wall, where the shorter depth
quickly builds up resistances to the movement of the insulation, creating
less dense spots, leading to slump. It seems that since friction against the
studs (or rafters in roofs) is also responsible for void spaces, and a need
for multiple holes, or the use of a filler tube, that the deeper cavities and
lack of studs in the mid-wall would reduce the troublesome friction, there
by reducing the need for as many holes. However, holes are no big chore,
so using them at top and bottom, every stud space, seems the way to go.
Cellulose slump should only happen when insulation is not packed to its
natural settling density, which is perhaps 2lb/cuft. So, if we blow in more
than that (~3.5/cuft), spread out thoughout the wall, it would make sense
that slumping would simply be impossible.  Do you know something that
I don't know?   Perhaps the lack of friction increases slump, but so does
vibration, over time.  I am doing a project this summer, with even larger
bays than Jefro's project, and I would sure appreciate any real-world
information that you can share (links, etc) on the subject of slump in
very thick walls, as well as verification that you don't really know, if
that is the case. I would like to know if I need to create friction, or
perhaps create a support membrane at a 4ft height. Perhaps I will
call a couple of manufacturers, to see if there is additional com-
-pression at full height wall depths (weight), when there are not
a lot of close surfaces to create friction.   There do seem to be
some factors that are beyond just thinking it through. Perhaps
I will do a few walls in different ways, then have an IR scan
done after a couple of years.

Thanks in advance;
-Laren Corie-
Climate Responsive Solar Building Design Since 1975
www.LarenCorie.com