permaculture

[drducc@aol.com]

   I have looked into geothermal heat pumps, and they do seem more 
sustainable and efficient than other forms of electrc heat, but they 
are clearly still dependent on the power grid with all the attendent 
concerns.  I went to a straw bale building workshop in Minnesota 
(northern US) where a more primitive use of geothermal looked 
intriguing.  The buider dug a trough several feet deep.  He installed a 
vapor barrier to keep radon from percing up, then a gravel bed, then a 
perforated pipe (bottom only perforated).  This ran through the ground 
to the surface  where it functioned as the air intake for the home's 
heating system with a heat exchanger to prevent heat loss.  I do not 
remember the details of the furnace.  I know there was wood back-up.  
The purpose of the underground pipe for air intake was to prewarm or 
precool outside air.  It made sense to me.

Debbie