RMH Reversing when house is warm

Hello, I have an 8" system running 30' through cob (including turns) exiting horizontally and then rising 5' outside. The stove has worked fairly well, it is still a new system so pretty cold still, my cob bench hasn't yet warmed up.

The stove was performing fine, but the moment the house (also cob) warmed up to the 70F area, my stove began reversing and dumping smoke into the house. I would like to put a taller chimney/riser on the outside, but am afraid it might cool the gases too much. Any ideas what is reversing my air flow?

Sounds like you need MORE chimney, not less....up over the roof of your house....10' away from or 4' higher than any thing close......

is single wall okay to use or do I need to insulate? The roof line is 12 feet so sixteen feet of rise would cool the exhaust pretty low wouldn't it? Thanks for the reply.

Daniel Ray : A second vote for more chimney, we definitely know that the Lee or Downwind side of the house is preferable, On paper I can prove that there

SHOULD BE a sweet spot just under the peak of the roof at that location, the problem of defining the best place for your final exterior chimney is the

very likely event of a major 2-3 day storm coming from another direction. We can't all live in places with stable winds blowing from the same direction for an

entire heating season. That 3 day storm of the decade Could give you even more problems than you have now, throw in a power loss due to the storm

and most of your neighbors will be sitting in cold dark houses.

Because of this built-in potential problem 'Convention Wisdom' states that you should install your final vertical chimney on the Lee side of the house and it should

top the peak of the roof by 4'-5' and be at lest 10 ' away from anything beggar than a TV antenna!

The easiest way to insulate your exterior chimney is to go with commercial grade insulated pipe, the problem with D.I.Y. is the potential to end up with wet

Insulation - Bad or Frozen Insulation - Very Bad!

Also you need to be aware of the potential for difficulty in starting a fire in your Rocket Mass Heater RMH, when it is cold if you have any exhaust fans running,

a big culprit is a clothes drier ( for the next 4 months you are going to want that humidity in the house anyway) also possible culprits are a bathroom exhaust fan

or the exhaust fan over your kitchen cook stove !

While you may be lucky, and never see a problem, you should google Stack Effect, and Whole house stack effect! These problems can occur with most other types

of Wood stoves too!

For the Good of the Craft ! Big AL

Thanks everyone, got the vertical pipe up over my roof and it is burning spectacularly now. Not only did it fix the reversing problem, but it also increased my barrel temp. from 400 to 600. Thanks again. I'll post some photos some day.