[Greenbuilding] Cellulose settling

[John Straube]

I agree with Loren -- there are no facts to support the contention that a
DIY dense pack will be a problem.
It is pretty hard to screw up dense pack cellulose or even damp spray
relative to other types of insulation. DIY insulation is almost always
installed better since the installer really cares and spends lots of time.
Weatherization people from all areas of the country who insulate homes and
then infra-red camera inspect constantly tell me that cellulose installs
better than any other practical insulation based on real-life inspections.
Some fibreglass products are now appearing that are blow-in and spray in (eg
JM Spider)to solve some of the poor quality install issues FG has. 

Dr John Straube
Associate Professor
Dept of Civil Engineering & School of Architecture
University of Waterloo
Waterloo, Ont., Canada
www.civil.uwaterloo.ca/beg
 

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Laren Corie
Sent: Thursday, July 27, 2006 10:07
To: greenbuilding at listserv.repp.org
Subject: Re: [Greenbuilding] was Diminishing returns / obsessingover
bridging


"Lawrence Lile" <LLile at projsolco.com>

> DIY blown-in cellulose, installed between existing studs
> and not done by a pro will probably settle and have gaps.
> 
> --Lawrence Lile

     I have seen no factual basis for such a statement.  There have
definitely been bad blown-in wall installations, by unscrupulous pros who
have cheated homeowners by using too little material. However, there is
nothing to suggest that a DIYer would ever short himself, when the only way
to tell that the wall cavity is full is that the blower stops moving
insulation and the hose buckles.  You simply fill the hole until it won't
take any more insulation. Cellulose will naturally
settle to roughly 1-1/2 lbs/cu ft density.     It gets blown into walls
at between 3.25 and 3.75 lbs/cu ft. So, it is packed in way tighter than its
natural settling density (like a spring, or foam rubber in a cushion).
Vibration will not cause it to settle. It does the opposite. It will cause
it to expand into every tiny area. Since there is far more cellulose in the
wall cavity, than its natural settling density, it simply can not slump. It
would be highly unusual for any area of a wall cavity to remain empty when
that same cavity was filled with insulation.  Locating the holes is not a
complicated task.  A hole near the top, and another near the bottom, will
give even enough packing for no slumping to occur in normal height walls.
Taller walls simply get an additional hole. Since the insulation value of
cellulose is in the fibers, instead of in the gaps between, there is no loss
of R value by increasing the density over that used for loose fill
installations. At either its loose fill density, or the 'dense-pack'
density, the R value is around 3.7-3.8/in.

However, there has been evidence that some foam insulations
can lose their bond with studs, leaving gaps where air can pass.  This is
why gaskets are beginning to be used around windows and doors, instead of
foam fills. This loss of contact should not happen with 'dense-packed'
cellulose, even in 
narrow spaces, where there might be frame movement.

-Laren Corie-
Natural Solar Building Design Since 1975
www.LarenCorie.com

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