[Greenbuilding] earth tubes

[nick pine]

RT <Archilogic at yahoo.ca> writes: 

>     http://goo.gl/l71Rm

>The alternative approach uses an underground glycol or 
brine loop with a heat exchanger located at the entrance 
of the heat recovery unit. The literature reviewed strongly 
suggests that operating EAHXs 24/7, year round, 
is not beneficial...

A small pipe with water below the frost line can use the soil's
heat capacity (about 30 Btu/F-ft^3 at US R1 per foot)
with no mold issues.

>... in the middle of summer it may be beneficial to stop 
the EAHX at night and draw air directly from the outside
if it is cooler.

My Phila simulations using TMY2 hourly weather data
say night ventilation can make an airtight house comfy
for all but 2 weeks in August, when a small AC for 
dehumidification and water filled earth tubes for cooling 
can work. Running earth tubes too often (when night
ventilation can work) overheats the soil.

Nick