SB: Re: A couple of notes about no pin systems from Maryland

["Robert W. Tom" <archilogic@yahoo.ca>]

2/25/02 3:27:48 PM, "Rene Dalmeijer" <rened@cistron.nl> wrote:

>Sam wrote:
>> I retrofit an old house by ripping out the interior walls of the building
>> and adding bales on edge to the existing plaster walls on the interior
>side
>> of the exterior wall.
>
>I would be very wary of the above approach to SB retrofitting of an existing
>building. The best place, moisture wise, for the bales is on the outside.
>This does complicate things if the roof overhang is not big enough. In most
>cases you will  have to add extra roof. 

EuroRay and Maryland Sam;

I  would suggest that if an existing building is being retrofitted with bales 
in the walls, then in all likelihood, the insulation levels in the roof are also
in need of some serious upgrading.

I would also suggest that the insulation cavity which the existing roof 
framing  provides will likely be too small to accommodate levels of 
insulation to  complement that of the SB in the walls.  
It really doesn't make much sense  to have R-30 to R-50 walls and 
only R-20 ceilings.

One could make the existing rafters into parallel chord trusses,
by spacing a new top chord away from the existing rafter (using plywood
or OSB gussets ... or sheet metal clips + wooden standoffs) to something
like 24" overall depth (allowing for 18 -20 inches of insulation and 4-6 inches
of ventilation air space).

In doing so, the finished roof is raised by about two feet allowing one 
to extend the  eaves out past the bales without cutting off the tops of 
doors and windows.

                                     === * ===

One point that EuroRay meant to touch upon but forgot to do so was 
the matter of Sam's plaster-butting-up-to-exposed-wooden-posts 
detail.

Wooden posts shrink and expand with the seasons and plaster shrinks 
upon drying, both of which result in nice, big honking cracks at the joint
between the two dissimlar materials.

Those who paid attention to the Interior Air Barrier 101 lecture will
know that each of those joints is a potential point for interior-sourced
moisture to find it's way into the straw, piggy-backed onto air leakage
and heat loss and the result could be localised fetid goo brew (a term
coined by Sam himself long ago, right here on this List).

Special attention must be paid to those joints (and other discontinuities)
in the air barrier )  and detailing provided to eliminate or at least minimise
air leakage at those points.

--- * ---
Rob Tom
Kanata, Ontario, Canada
<ArchiLogic@yahoochaff.ca>
(winnow the "chaff" spamguard from my edress in your reply)

Please visit http://www.theHungerSite.com daily



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