Need info about soil roof on a log house.

nicksanspam at nicksanspam at
Wed Mar 11 12:31:09 EST 1998

Roy  <"wyomtnman"@prodigy\"nospam\".net> wrote:
>I remember the old buildings on our ranch in Wyoming with the soil covered
>roofs... built in the 1890's, and were still standing (with sod roof) as
>of last year!

They musta done something right.

>The cabins were about 20' x '40, a ridge pole of pine approx. 14" diameter...
>soil was about 8" deep on the roof, planted in cheat grass and other grasses.

Sounds like lots of thermal mass but not much insulation, R1/12/inch for
soil at 15% moisture content? A thermal conductance of 20x40/(8/12)
= 1200 Btu/h-F for the ceiling?

>The cabin walls were log as well, about "10 in diameter, and the floor was

R5 walls, roughly, with a thermal conductance of 192 Btu/h-F and an
R10 floor with a conductance of 80 Btu/h-F between the inside and
the average annual air temperature?

>Again, this was in Wyoming where the winter temperatures got to -35 degrees
>Fahrenheit, yet the inside of this unheated log building stayed above
>freezing.  It was heated by about 30 chickens (a chicken coop when I was a
>kid), no problems and no other heat source.

An indoor chicken coop? I wonder about the smell. If there were ever a need
for an air-air heat exchanger... A standard 4 lb chicken makes about
35 Btu/hour, ie about 10 watts, according to the 1993 ASHRAE HOF, so
30 chickens would make about 1050 Btu/hour or 300 watts. Doesn't sound like
much heat. Enough to raise the indoor temp of that cabin about 1050/1472
= 0.7 F. I guess you got some heat from the ground as well.


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