[Greenbuilding] insulating on sheathed roof

[Keith Winston]

Spray on is probably another word for damp-spray, which isn't the same 
as loose-blown. But it's also very different from dense pack, so I agree 
with your point Bob, and it was my first thought too.

I can't even imagine that 1.5" of damp spray wasn't MUCH better than 6" 
of fiberglass, so I think something here is fishy.

Keith


RH Irving Co Inc. wrote:
> Robert
> Sounds like you are comparing apples & oranges.
>
> "wet-sprayed" cellulose is not the same as dense pack cellulose.  "Cellulose
> insulation (spray on)" sounds like loose spray (like into an attic). 
>
> Did they test DRY dense pack?  At what density?
> Bob Irving
>
> -----Original Message-----
> From: greenbuilding-bounces at listserv.repp.org
> [mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Robert Tom
> Sent: Thursday, January 03, 2008 3:47 PM
> To: greenbuilding at listserv.repp.org
> Subject: Re: [Greenbuilding] insulating on sheathed roof
>
> Prior to the Listserver [BURP] before the holidays, and now that the  
> archives are accessible someone wrote:
>
>   
>>> Why do you say blown cellulose requires no vent space?
>>>       
>
>   
>> dense packed cellulose stops almost all air leakage,where as fiberglass  
>> needs venting
>>     
>
> The above seems to imply that dense-packed cellulose functions as an air  
> barrier, a myth that was previously promulgated on this List years ago by  
> a Frank Lugano who used to (and perhaps still does ?) write as a "  
> weatherisation expert" for Fine Homebuilding magazine.
>
> If no vent space is required in a cathedral ceiling it will be because the  
> air barrier strategy is effective.
>
> Dense-packed cellulose is *not* an air barrier material.  " 
> In 1985, the Canadian building codes recognised that building assemblies  
> needed to have an effective barrier to limit air infiltration/exfiltration  
> in order to avoid the moisture problems that result from bulk moisture  
> transport via air leakage.
>
> In 1988, an external research contractor for CMHC undertook a project to  
> evaluate the air impermeance of some common building materials and the  
> results of that testing were published in the CMHC report "Air Permeance  
> of Building Materials". That ~12mm-thick report is free to all Canadians  
> and for a nominal fee to others, from CMHC.
>
>  From Table 6 of that report, the IRC (Institute for Research in  
> Construction at the National Research Council of Canada) classification  
> for air barriers systems is:
>
> 	Type I : max air flow @75 Pa = 0.15 L/s-m^2)
> 	Type II: 0.10
> 	Type III: 0.05
>
> Table 8 in the above report lists the effectiveness of the materials in  
> descending order and among the materials tested were fibreglass batt  
> insulation and wet-sprayed (ie dense-pack) cellulose .
>
> Glass wool insulation is third from the bottom in the table, with average  
> air flow (Q-avg) listed as being 36.7327 L/s-m^2 @75 Pa.
>
> Cellulose insulation (spray on) was last in the table, just below  
> vermiculite, with Q-avg listed as being 86.9457 L/s-m^2 @75 Pa.
>
> Neither fibreglass nor cellulose were sufficiently air-impermeable to  
> achieve a rating.
>
> To be fair, it should be noted that the glass wool insulation tested was  
> 152 mm (~6") thick and the cellulose thickness was only 38 mm (~1.5").
>
> I'll leave it to interested parties to do the arithmetic to determine  
> effective air permeances for the specific thicknesses that they are  
> considering.
>
> 			=== * ===
>
> And speaking of listserver [BURPS], I sent out the following message  
> almost immediately after reading Duck Foo'd's message about the impending  
> Listserve maintenance/potential disappearance but apparently it was too  
> late to get distributed by the Listserver.
>
>
> ================ Forwarded Material ===================================
> On Fri, 21 Dec 2007 11:03:02 -0500, Robert Tom <ArchiLogic at yahoo.ca> wrote:
>
>   
>> Duck Foo'd wrote:
>>
>> [snipped & pasted]
>>     
>>> server migrationThere may be delivery delays and other burps, including  
>>> a total vanishing act
>>>       
>> Recalling the last time that the GB List disappeared, (the last time we  
>> did not have the benefit of a warning -- thanks, Mark for this one) I've  
>> just done a few mouse clicks to create a surrogate GB List just in case  
>> there are unforeseen glitches in the migration process and the down time  
>> gets extended to a period of weeks or months.
>>
>> http://groups.yahoo.com/group/GB-r-us/
>>
>> If anyone would care to become the defacto List Owner, drop me a line.
>> S'awright ? S'awright.
>>     
> ============ End of Forwared Material ==================
>
>
> The above back-up is in existence and can be in place for future [BURP]s.
>
> If anyone does subscribe as insurance for the future, I would suggest  
> opting for the
> "NO EMAIL" mode of mail reception until such a time as this Listserver  
> does go down and the backup is needed.
>
> I also noted that this List' archives were completely inaccessible (ie  
> non-existent) during the down-period. Perhaps what might be done is CC  
> messages to the back-up GB list so that in the event of a failure of this  
> Listsever, there will still be an accessible archive.
>
>
>