[Cob] Passive cooling

[Leslie Moyer]

paul wrote:
> Hi, here's an interesting article about passive air conditioning by use of a 
> "cooling tower" (a Persian design.)  <<snip>>
>
> http://www.thefarm.org/charities/i4at/lib2/aircool.htm

I don't understand what benefit is derived from having the cooling 
function up high in the tower.  It seems to me that the same benefit 
could be derived from just doing the evaporative cooling at the bottom & 
exhausting heat out the top of the tower, since heat naturally rises.  I 
can see that the tower would help to circulate the air, creating a 
downward fall, but, if designed right, this could be accomplished in 
other (maybe less expensive) ways.  My understanding of "Persian design" 
is that a wind scoop catches air at the top of a tower, then pulls it 
down to ground level (or below), where it then meets the evaporative 
chamber.

The house we're designing now has passive cooling built into the 
design....here's what we're doing:

House is bermed into a south-facing hillside.  We have a tower that sits 
several feet above the highest point of the house with an exhaust fan 
and operable windows.  (This will likely double as an outdoor sleeping 
porch and/or viewing tower.)  Prevailing winds come from the 
south-southwest and building site is high enough to get a good breeze 
most of the time.  Ground floor is all one level except for one 
slightly-elevated dining room (elevated about 2 or 3 feet).  Elevated 
dining room has a north-facing patio, bermed deeply into the hillside.  
There is a water feature (waterfall and evaporative vegetative "green" 
wall) on the north outdoor patio (creating the "evaporative" function, 
as well as a beautiful patio).  On a hot day, all windows can be closed 
except the north-facing patio doors and the cooling tower windows and/or 
exhaust fan (if a mechanical assist is needed).  Prevailing winds will 
create negative pressure on the north side of the house, drawing cooled 
air down the patio walls and in through the patio doors, where it will 
sink to the ground floor, forcing heated air out the top of the cooling 
tower.

We have a couple of benefits over the website design:  We get to enjoy 
the evaporative cooling feature (patio & living wall to use as outdoor 
living space) AND we also get to use the tower as living space. 

Also, evaporative cooling works best in very dry climates....working 
less-well the more humid a climate is.  Therefore, in our humid climate 
(Oklahoma), the earth-berming lends an additional cooling benefit.  
Below-grade cob doesn't work, however, so that's a glitch here on this 
cob list.

An architect is working on plans, so some of this is unknown as-yet, but 
those are the plans and she's working them into our design.
--Leslie