Chimneys : The Six Commandments
Chimney does not belong to the house, but to its appliance.
More carefully sized to the heating appliance.
Be tightly constructed.
Be located within the heating envelope of the house.
Terminate at or near the highest point of the building.
The best resource for good wood heating systems and chimneys is a book by John Gulland called: The Fireplace, in the house as a system.
also of interest: www.woodheat.org and wood appliance chimneys.
Also check out information about exhaust fans and chimney backdrafting by looking up "Spillage Susceptible"