[Fwd: Re: Cob: Thermal mass and climate]

[Howard]

Debra Freeman wrote:
> 
> I'm confused about wanting to get solar gain, say, through a glazed window
> facing south, if you live in a climate that's hot and humid in the summer.
> 
You want to shade the south glass in the summer, a roof overhang is how we usually
do it, as the solar design books suggest. If the wall is too tall you may want to
construct an awning or hang some greenhouse shade cloth from the eave. (which will
also keep the birds from killing themselves on your glass)


 Darel writes: "> Certainly not
> on the south side, unless you have some other mechanism to get the solar heat
> inside.

Windows in a fully insulated south wall is fine "mechanism" for getting the heat
inside.:)  Building with cob it may not be necessary to insulate the south wall. The
ideas you mention for adding on are sound except possibly the building of one room
two stories high. The second floor system is often necessary to brace the walls. 


 "Earth
> tubes should be fine anywhere.  Why do you feel its
> > inadvisable?" I read an article from the U.S dept of energy (which may be
> biased?).  I quote:
> 
> "Earth cooling tubes are likely to perform poorly in hot, humid areas, because the
> ground does not remain sufficiently cool at a reasonable depth during the summer
> months. Moreover, dehumidification, another equally important aspect of cooling,
> is difficult to achieve with earth cooling. Mechanical dehumidifiers will most
> likely be necessary."
> 

The USDOE is right on this one. Not that the ground doesn't stay cool enough in the
summer, it actually does well at a 48" depth, but the humidity is the issue and that
I expect is the cause of the horror stories you've hear about.  I did two houses
with ECA tubes in the early 80's and was fortunate to have TVA send out a crew of
scientists who set up testing in one of the houses. They arrived at the end of a
record breaking heat wave but the tubes did manage to cool the house to 76 on a day
that was 97 outside but because of the humidity it did not make it comfortable plus
the potential for mold.  We had hoped to reach dew point in the tubes and had
installed the tubes to drain but that did not happen. Dehumidifiers would add heat
back into the space defeating the purpose of the tubes. We often thought of
retrofitting the closet in which the fan was housed with a large desiccant filter
but that never happened as the owner instead bought a small AC unit.  I wouldn't
bother with tubes and especially not in the walls because I can assure you it will
not be worth the effort and expense. Also PVC?....yek, its one of the most poisonous
plastics. Cob is an excellent mass material so I would not put water in it but some
containers inside the house perhaps as a plant stand or table base might be good if
you feel you need more mass.


> 
> Darel responded: "I'd have to guess on this and say no.  I recall reading
> >something about this and it said it wouldn't be a problem. There may not be that
> >much of a temperature difference to cause condensation."
>

I agree.

I think shading, ventilation, serious insulation and a plunge pool near by are the
keys to staying cool in AR without AC.  
 
Good luck,

Howard
www.ecoarchitech.net