Most houses in my neighborhood have chimneys with three flues. Some have the
flue heights staggered, while some are all the same. Does the staggering
help prevent smoke exiting one flue from going down another? If so, how
different do the heights have to be to be effective? Does the order matter
(SML or SLM)?

Also, how much space does there have to be from the highest flue to a
chimney cap?

Thanks.

user wrote:
Most houses in my neighborhood have chimneys with three flues. Some have the
flue heights staggered, while some are all the same. Does the staggering
help prevent smoke exiting one flue from going down another? If so, how
different do the heights have to be to be effective? Does the order matter
(SML or SLM)?

Also, how much space does there have to be from the highest flue to a
chimney cap?

Thanks.



Are you sure the two of the flue liners aren't
just decoration? There is no reason to have
three operating flues unless you have several heat
sources.


The height of the flue above the chimney cap is
primarily a function of looks (and maybe how much
snow you get). Three or four inches is probably a
minimum. The actual height of the flue is based
on a minimum horizontal distance from the roof
line and height related to that point. It is
based on draw capability and blockage of air flow
by a near surface. Local codes may vary.

heat rises.

Hi. Thanks for the response.

The three flues are operational: two fireplaces and furnace.

Sometimes when I use the upstairs fireplace, the downstairs family room
smells of smoke. I've heard that this can happen when smoke exiting one flue
goes down the one next to it. I also heard that by varying the heights of
the flue caps, that is less likely. My flues are flush with each other and
the chimney. I'm thinking about adding extensions to create different
heights.

Are you sure the two of the flue liners aren't just decoration? There is
no reason to have three operating flues unless you have several heat
sources.


The height of the flue above the chimney cap is primarily a function of
looks (and maybe how much snow you get). Three or four inches is probably
a minimum. The actual height of the flue is based on a minimum horizontal
distance from the roof line and height related to that point. It is based
on draw capability and blockage of air flow by a near surface. Local
codes may vary.