[Greenbuilding] Barra system

[Keith Winston]

Hi Laren, thanks for some of the details on your system. Always 
interesting to hear different approaches.

Another thing that will make your system a bit safer from condensation 
problems is the plastic pipe: less susceptible to condensation due to 
lower conductivity than both metal ductwork and concrete.

I've often wondered about the sand storage approach, and perhaps been 
overly judgmental (I do that a lot... oops) because I've become a little 
obsessed with comparing it to saturated sand... Dry sand has less than 
1/3 the volumetric heat capacity as water, saturated sand has twice 
that. More to the point, while dry sand has twice the thermal 
diffusivity as water, saturated sand is about 4 x that! But of course, 
if you've got enough mass, and enough surface area of heat exchanger, 
then none of that matters... And I'd never try thermal exchange with air 
in a saturated storage bed, that's asking for trouble.

If you have any further info available on your building 
ideas/experience, I'd love to see it (besides your regular valuable 
contributions here). I see a few things on your website.

Keith

Laren Corie wrote:
>  From: Keith Winston <keith at earthsunenergy.com>
>
>   
>> I think any system that has your house air flowing
>> through an uncleanable and uninspectable is flawed.
>>     
>
> Hi Keith;
>
>  I had that concern with my early 'pancake' radiant underfloor storages,
> which used stone (ala Doug Balcomb's house), as well as quite a few
> practical problems that cropped up doing many projects.   The use of
> concrete blocks solves only some of them, but added considrably to the
> cost, while reducing the storage capacity. My solution, by 1982 was to
> use standard HDPE corrugated (non-perforated) drain tubing, running
> through a foot of sand, on one foot centers. There was never any reason
> to worry about condensation, and inspections of the most critical areas
> of the tubes was possible, through the large floor vents and plenums,
> and never showed any signs. Most ducting, in most houses, never gets
> inspected or cleaned, and is often far more exposed to the large temp
> differences that can cause condensation.  The temperatures in the heat
> store are very stabile, compared to the living space.   The chance of a
> situation such as condensation, to create pooling, then warmth to pro-
> -mote the growth of something like legenella, is so improbable as to be
> insignificant.   I am totally satisfied, that there is no reason to be able 
> to
> inspect, or even clean every foot of a system that is well sealed, every-
> where except at its very inspectable ends.
>
> >From "raymond pokorny"
>
>   
>>> remember the basics folks.   one cubic foot of water holds the same
>>> amount of heat as one thousand cubic feet of air.  both are fluids.
>>>       
>
> Actually, it is about 3500 ft³ of air.
>
> -Laren Corie-
> Natural Solar Building Design Since 1975
> www.LarenCorie.com
>
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