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re: underground house...
8 jan 2000
wrote:
>never heard of a camel's nose. what is it?
i think that's just john hait's name for a heat exchanger
with some internal latent and sensible heat storage and
bidirectional flow. you know, like a nose...
>>hait has an interesting way of providing fresh air and conducting and
>>storing heat in the earth around the house, like this:
>>
>> earth earth earth earth
>> uuuuuuuuuuuuuuuuuuuuuumbrella
>> solar gain --------------------- <-> uuuuuuuuuuuuuuuuuuu
>> uu \ | | \ upper earth tube uuu
>> uu | house | \ uu
>> lower earth tube<-->| | (use courier font) \
>> ---------------------
>>
>>the lower earth tube slopes up to the house (to make an igloo-like
>>heat trap) and enters the living space at floor level. the upper earth
>>tube enters at ceiling level, and slopes down to exit at the same outdoor
>>level as the lower.
>>if the house becomes slightly warmer than the surrounding earth,
>>outside air naturally enters the lower earth tube and warm air
>>flows out of the upper one.
>not if both earth tubes exit at the same level, you have
>no chimney effect and the air will flow thru the tubes
>in either direction based mostly on any small differential
>pressure between the 2 tube exits due an outdoor wind.
let us reason together. what happens if there's no wind,
and the house somehow (eg solar heat) becomes warmer than
the surrounding earth? let's redraw this, simplified,
in courier font...
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii
i |
i i |
70 f earth i 80 f i75| 70 f earth
i room i |
(i is insulation) i i | <--no insulation here
------ i ------
--------------------------
now we have 2 columns of air at different temperatures, 80 and 75 f.
the 75 f air is denser, so it moves downward and draws in some air
from the tube on the left, which moves the room temp closer to
the earth temp, until flow ceases.
>> if the house becomes cooler than the surrounding earth, flow reverses.
now let's reverse the temperature difference and further simplify the
picture by connecting the outdoor ends of the earth tubes, since
they are at the same "potential"...
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii
i |
i i |
70 f earth i 60 f i65| 70 f earth
i room i |
(i is insulation) i i | <--no insulation here
i i |
| |
------------
now it's clearer that the room air sinks and the air in the right hand
"earth tube" rises. this closed loop configuration is thermally more
efficient than warming and cooling 100% fresh outdoor air all the time.
these houses apparently work well, but they require lots of digging and
insulation. some directions for possible improvement are:
1. close the loop, with less outdoor air, and add some controls.
2. store solar heat for less than 6 months, in non-polar places.
3. build them above ground, with less labor and materials.
the above-ground version might have a simple geodesic structure made
with steel drums or telephone poles supporting a hair net thingy made
with old tires and little pieces of nylon rope, with plastic bags of
dirt over that, another hair net over that, bags of leaves, peat moss,
vermiculite, etc. check with your building inspector.
>did he suggest ways to remove condensation?
slope the tubes downhill, as i recall.
>> 5. provide a place for the warm air to go.
>> 6. provide a place for the cool air to go.
>
>what does the above mean?
ensure there's a complete air circulation path.
nick
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