[Greenbuilding] Cellulose settling

Thu Jul 27 12:44:59 CDT 2006

I've never seen anything like that. If you just poured the material in, 
or used a very under-powered blower, I could understand settling, but 
you pack it in quite tightly with a properly operated machine. However, 
I am EXTREMELY unimpressed with most netting jobs. I was initially 
excited at this approach, and now I think I hate it. First, due to  a 
bad experience with an installer. We had a conversation that went like 
this:

Me: wow, that netting isn't installed very tightly. And I don't think I 
like the face-staple approach.
Him: you don't need it any tighter. And it's very hard to do anything else.
Me: wow, the cellulose is really loose in there. I can tear a hole in 
the netting and reach my had straight through without a problem. In the 
ceiling, I can feel that there's almost no material on top
Him: I can't pack it any tighter, or the sorta loose netting will bulge 
out and keep the sheetrock from attaching right (pop screws).
Me: (nothing, since I've fallen mute in disbelief)

And this was an installer I was generally impressed by! IF you install 
the netting very very tightly (which is hard) then you can pack it more 
tightly. But it still leaves two channels up either side of each stud 
where air will freely move around. That is, the only way (as far as I 
know) to install the netting tightly is to lip-staple it, which means 
reaching around and stapling it to the SIDES of each stud, perhaps 
1/2-1" from the face. When you properly fill the cavity, it bulges out 
to meet the sheetrock in the middle, but can't do so immediately 
adjacent to the stud. So it leaves a little channel. Hopefully that's 
clearer. The installer mentioned above face-stapled the netting, and I'm 
unconvinced that that approach can work (though it does avoid the 
channel issue). (BTW, as far as I can tell the only way to do any of 
these netting jobs is with these special german staple guns that work 
like automatic machine guns, firing hundreds of staples a minute. You 
develop a rhythm so you can lay down a track of them along each stud. 
They're hard to find here, especially in the wide-crown version. Using 
normal pneumatic staple guns, much less anything lesser, is almost 
implausible).

I guess I'm left liking damp-spray, and I'd like to see better 
drill-&-fill-style install approaches, that don't use netting but assure 
even fill. I do think the old standby two-hole drill & fill (that Laren 
mentioned) is good, especially if you prepped the wall during 
construction by avoiding barriers, and sealing leaks (which you should 
have done in all cases except, arguably, spray-in-foam).

I'm totally open to being informedly corrected about anything I think I 
know. I do have a blower, but I'm not a professional installer (very 
often :-)...

Keith

John Salmen wrote:
> Had a chance to look at an installation done for a homeowner who was in the
> building industry (it was done with a net - drywall off) - at 6 months there
> was 6-8" settling and the owner topped it off - at 12 months it was down 2".
> Original installer did everything to spec. for density of installation. It
> was done this way as the owner wanted to ensure a properly insulated wall
> and didn't trust the material.
>
> A void is inevitable - the material spreads to fill and settles under its
> own weight, it isn't pixy dust.
>
> John
>
> TERRAIN E.D.S.
> 4465 UPHILL RD
> DUNCAN BC
> CAN V9L 6M7
> PH 250-748-7672  FAX 250-748-7612 CELL 250-246-8541
> terrain at shaw.ca 
>
> I had three pieces of limestone on my desk, but I was terrified to find that
> they required to be dusted daily, when the furniture of my mind was all
> undusted still, and threw them out the window in disgust --Henry David
> Thoreau
>
> -----Original Message-----
> From: greenbuilding-bounces at listserv.repp.org
> [mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of John Straube
> Sent: July 27, 2006 8:07 AM
> To: greenbuilding at listserv.repp.org
> Subject: [Greenbuilding] Cellulose settling
>
> 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
>
> -LittleHouses- http://groups.yahoo.com/group/LittleHouses
>
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-- 
Keith Winston
Earth Sun Energy Systems
3927 Madison St.
Hyattsville, MD 20781
301-980-6325
keith at earthsunenergy.com
www.EarthSunEnergy.com