Mike Gillingham : I think that your present system is trying to tell you that you have some big problems with it !
I would get a professional in to see what is going on! Most Likely, you could easily find that the RMH is making your system worse.
You also need to due little research on "STACK EFFECT" and 'Whole House Stack Effect', Understanding the concept of Stack Effect,
especially as it effects Rocket Mass
Heaters RMHs, and very specifically RMHs in basements, is easy, Grasping the realities are much
harder, Someone turning on the fan in the hood over your Kitchen
oven, Or running a Clothes
Dryer that vents outdoors can cause
your Rocket to Backdraft, and fill your Basement and House With Smoke !
I definitely would plan on A full exterior Chimney that exhausted on the lee side of the house and ended 4 -5' above the ridge line of
my house, Anything less may work, but it would be several heating seasons before you would know For Sure !
For the Craft, Think like Fire, Flow like a Gas, Don't be a Marshmallow! As always,comments and questions are Welcome and Solicited
Big AL