Cob/Earthbags & passive solar

[Otherfish at aol.com]

pat & all interested
re passive solar & earthen buildings:
as with cob, so will be the case for earthbag & any other form of construction
-the passive solar part of a design needs to be balanced to the location's
climatic conditions
-earth buildings have lots of thermal mass & will work good in the climate
they are in if they are designed to store up the suns heat to the tune of
comfort on a 24 hour cycle - if they are in a hot climate then they need to be
able to NOT take in solar gain during the hot time of the year to any greater
extent than what the heat loss will be during the nights at that time of year
- if its hot, hot, hot all the time & all year long then thermal mass is
probably not a cool idea. (ouch) 
-as in all things, passive use of the suns energy is a balancing act !!!
-Edward Mazzria's book on Direct Use Of The Suns Energy is a worthwhile read
re this !!! 

re deterioration potential comparison of earthbag vs cob:
if I understand earthbag correctly, it is basically damp loose earth which is
compressed in the bag by tamping after the bag is placed in the wall - sort of
like rammed earth where the bags are the forms - the  concern I expressed
about the stability of this form of construction is that unless there is some
form of stabilization in the earth mixture itself, if & when the bag
eventually deteriorates then what is there to keep the earth still in the
wall? - this is further complicated by the fact that the earth in one bag is
in no way connected to the earth in another  bag except by friction between
the bags & the mechanical bond of the barbed wire between the bag courses &
the earth as constrained by the tension surface of the bags    
-while cob is not made of such discreet compressed earth units & is provided
with continuity by the threading of the straw throughout the entire earth
matrix & the bonding of the successive cob applications into a monolithic
whole by working wet into wet as much as possible so that in a sense the whole
becomes one big continuous dried mud shape ( this is where quality control of
the construction in cob is of paramount importance )

but you probably already knew all this

at the first Blackrange Lodge colloquium we built a tamped foundation of
plastic woven sandbags filled with some sort of a  pea gravel material
(volcanic origin, i think) & this was the base of a combo of liechmem & cob
walls - this seems like a good use so long as the bags are protected from UV
deterioration - the plastic bags seem like good assurance against damp
foundation conditions deterioration  altho I'm not sure it is such a good idea
in seismically active locations

thanks for the reply posting re your earthbag work
regards
john fordice
TCCP
otherfish at aol.com