Matrix
Insert
Installation
and
Operation
Manual
46
______________________________________________________________________________
9.6
MINIMUM
CHIMNEY
HEIGHT
The
top
of
the
chimney
should
be
tall
enough
to
be
above
the
air
turbulence
caused
when
wind
blows
against
the
house
and
its
roof.
The
chimney
must
extend
at
least
1
m
(3
ft.)
above
the
highest
point
of
contact
with
the
roof,
and
at
least
60
cm
(2
ft.)
higher
than
any
roof
line
or
obstacle
within
a
horizontal
distance
of
3
m
(10
ft.).
9.7
THE
RELATIONSHIP
BETWEEN
THE
CHIMNEY
AND
THE
HOUSE
Because
the
venting
system
is
the
engine
that
drives
the
wood
heating
system,
it
must
have
the
right
characteristics.
The
signs
of
bad
system
design
are
cold
backdrafting
when
there
is
no
fire
in
the
insert,
slow
kindling
of
new
fires,
and
smoke
roll
‐
out
when
the
door
is
opened
for
loading.
9.7.1
WHY
THE
CHIMNEY
SHOULD
PENETRATE
THE
HIGHEST
HEATED
SPACE
When
it
is
cold
outside,
the
warm
air
in
the
house
is
buoyant
so
it
tends
to
rise.
This
tendency
of
warm
air
to
rise
creates
a
slight
pressure
difference
in
the
house.
Called
‘stack
effect’,
it
produces
a
slightly
negative
pressure
low
in
the
house
(relative
to
outside)
and
a
slightly
positive
pressure
zone
high
in
the
house.
If
there
is
no
fire
burning
in
a
heater
connected
to
a
chimney
that
is
shorter
than
the
warm
space
inside
the
house,
the
slight
negative
pressure
low
in
the
house
will
compete
against
the
desired
upward
flow
in
the
chimney.
There
are
two
reasons
why
the
chimney
in
the
house
at
right
will
cold
backdraft
when
it
is
cold
outside
and
there
is
no
fire
burning
in
the
insert.
First,
the
chimney
runs
up
the
outside
of
the
house,
so
the
air
in
it
is
colder
and
denser
than
the
warm
air
in
the
house.
And
second,
the
chimney
is
shorter
than
the
heated
space
of
the
house,
meaning
the
negative
pressure
low
in
the
house
will
pull
outside
air
down
the
chimney,
through
the
insert
and
into
the
room.
Even
the
finest
insert
will
not
work
well
when
connected
to
this
chimney.
