[Ferro List] 3 questions for Walter

[Janoahsh]

Ahh here we go again.  Thank you for asking this question Keith,
Condensation Buildup.
I think this problem comes and goes with temperature extremes and interior
use.
To Illustrate, I think A Sauna in Fairbanks with steam created by tossing
water on hot rocks would eventually destroy a porous cement wall unless a
dry heat could draw the moisture out before it cooled off. 
Sealing the inside might totally eliminate the problem depending on the
extremes possible.
As we have discussed before the problems can vary with climate, location and
use. 
I am beside my self figuring the best way to deal with the problem.  I think
there needs to be a provision for venting the medium with dry air/heat as
well as blocking moisture from entering
The sphere we are building will have lots of moisture created with green
plant transpiration, cooking, showers, etc.  I hope to capture most of it
with a passive condenser cooled by incoming water.
I also plan to incorporate vented tubes in the walls that will supply warm
dry air if needed to dry them out.
If a porous material is being used for insulation in a moist environment
there is bound to be build up unless there are other conditions that offset.
Janosh
-----Original Message-----
From: list-bounces at ferrocement.net [mailto:list-bounces at ferrocement.net] On
Behalf Of Keith B
Sent: Tuesday, February 26, 2008 1:39 PM
To: Ferrocement Discussion List
Subject: Re: [Ferro List] 3 questions for Walter

Hi Walter,

Any more details on what you are planning for your "insulating concrete 
layer"?  At 40 pcf for an all mineral lightweight mix, I would expect a 
thermal performance of R1 plus or minus a bit, but authoritative data 
seems notably lacking in the area.  Further, vermiculite or perlite 
mixes generally end up very porous, so I presume you are relying on your 
hard skin for waterproofing, but is there a risk of internal 
condensation build up in your coldest weather?  I ask because I've 
recently been reading a paper on an exotic system which suggests that 
one may be able to do better, both thermally and regarding permeability 
and water storage, with an OPC one.

kb

Walter Jeffries wrote:
> . We still need to do the insulating layer on the cottage roof  
> and then the final hard coat. That is a project for this summer.
>
> Here's a link to a model, ...insulating concrete layer over the roof...
>
> http://sugarmtnfarm.com/blog/2007/09/dog-house-bottles-roof.html

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