On Fri, 1 Jan 2010 12:00:20 -0800 (PST), Jim Wilkins
wrote:

On Jan 1, 10:38*am, Ned Simmons wrote:
...
Catalytic stoves are rated as high as 80%, while modern gas furnaces
are 90%+ efficient. But there are too many variables in woodstove
design and operation to rely on a single number. So a 2 to 1 ratio is
a conservative number, erring in favor of gas, and close enough to
debunk a claim of 40x CO2 emissions from a woodstove.
Ned Simmons

Ole Wik's wood stove book that Lindsay once sold has a performance
chart for the Jotul 118, the old one instead of the Black Bear they
sell now.
It gives the maximum efficiency point at 22,500 BTU/Hr with 3.1 Lbs/
hour of air-dried wood, 20% moisture content.

This mentions the same data point, 76% efficient:
http://hearth.com/econtent/index.php...ewthread/8911/
The chart apparently comes from Jotul's resource book "The Art of
Heating with Wood", which I haven't found to download yet.

I run my import copy hotter than that to eliminate visible smoke but I
burn on average only about two cords a year, in cold NH. People with
similar houses tell me they burn 5.

We heat with a firebrick lined welded steel knockoff of a Jotul that I
built 25 years ago. Two and a half cords takes care of our small 1200
sf house with lots of glass in ME.

This stove is the 16" model. I built others as small as 12", and three
behemoths that burned 4' sticks for the service buildings at a
boatyard.

--
Ned Simmons