Re: SB: skins of earth and cement

[Peter/Pam Martin <pmartin@islandnet.com>]

Greetings Rob Tom,

At 11:14 AM 09/29/2001 -0400, you wrote:

<much snipping here and there>

>"Cool, wet, winters " tells me that the exterior skin may be
>subject to extensive rain wetting throughout the winter season
>and "hot, dry summers" tells me that inward vapour drive may
>be the primary  mechanism by which that skin dries out
>(or more correctly,  dries in) during the summer months.
>
>If that is the case, then having a relatively vapour permeable
>earthen plaster on the interior would allow drying to the interior
>to occur as opposed to having a low vapour permeance finish
>that would act as a vapour diffusion retarder, keeping the moisture
>within the bales.
>
>If Beel were here, I have a feeling that he would be jumping up
>and down and trumpeting the immense capacity of earthen plasters
>to suck-up and store excess humidity, to released later ,
>
>I have a feeling that Beel would further suggest that earthen
>plasters as an interior finish would act as passive humidty regulators

Need one be cognizant, that during the winter, when some interior heating 
will be required, and even though the interior earthen plaster will store 
excess humidity, it would be preferable that the interior vapour permeance 
be less than the exterior permeance?  In Raquel & Greg's situation, would 
decreasing the permeance of the interior by applying an appropriate paint, 
while keeping the permeance of the interior skin slightly higher than the 
exterior, be a viable compromise?  This would have the effect of reducing 
the rate of release of humidity to the inside during times of inward vapour 
drives, as well as reducing the movement of vapour outward through the 
interior skin during the winter.  I guess it all depends on the amount of 
exterior wetting, the amount of vapour produced in the interior, the 
ability of earthen plasters to store humidity, etc., etc.  Peter.

P. & P. Martin,
1830 Millstream Rd.
Victoria, B.C., V9B 6E3
250-478-0073



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