[Greenbuilding] [BULK] Re: was Diminishing returns / obsessingover bridging

[Lawrence Lile]

Amazing!  Thanks!


-----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 8:07 AM
To: greenbuilding at listserv.repp.org
Subject: [BULK] Re: [Greenbuilding] was Diminishing returns /
obsessingover bridging
Importance: Low

"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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