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

[Beeguild@aol.com]

Rob Tom:

Good to hear from you again.  Ah, the difference a few degree days of heating can make....

The argument about a mismatch between bale walls and skimpy (or no in my case) insulation in the roof is a good one.  I actually have decided that bales in walls in my case are more of an environmental an aesthetic (sp?) statement than the sliced bread of energy efficiency.  Money should go to the roof.  In our case, I wanted heavy ceiling insulation, but had no headroom upstairs to play with.  

My solution was something like what Rob Tom outlined but the details differ.  We kept the existing asphalt shingles on but buried them under 9 in. of styrofoam which we ordered in 16'X4' lenghts.  On top of the foam we laid as purlins, scrap 1 in boards from the sawmill every 3 feet up the roof.  Those boards were screwed to the original decking with 11" self-taping screws.  On the purlins we nailed Ondura recycled paper/tar corrugated roofing sheets.  The only cold bridge to the outside were the screws.  To cut you off, I almost used strawbales instead of foam, but the prospect of   dealing with wet straw in the roof from a roof leak was too much.

Pole-wise, yes poles shrink away from the plaster in the winter and become a place for infiltration.  I am contemplating using a masonry pastry bag to fill those cracks, but have too many other things unfinished to complete that yet.   I may not bother and simply trust that the outer wall is tight enough to prevent massive influx of cold air, and as the other post indicated, I don't think moisture in these hear southernerns bales are ever going to be a problem unless a pipe bursts.

Sam Droege


> 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.