In order to determine proper chimney height above the roof, measure from the side
of the chimney horizontally. As you move up the chimney, the length of the measurement increases. Once
this measurement reaches 10 ft. this height on the chimney is your base height. The chimney must be 2 ft.
taller than the base height. If the chimney is closer than 10 ft. from the peak of the roof, the chimney
must be 2 ft. higher than the peak of the roof. The 2 ft. above the base height does not include the cap.
Most problems with woodstoves are caused by improper hookup or operation.. The biggest
problems concern not getting enough air through the stove or simply not getting catalytic stoves up to
proper operating temperatures.
A properly installed chimney is key to having proper draw. This is especially
important with use of a kit chimney, most masonry chimneys are built by contractors who are familiar
with the rules of chimney installation, however, most kit chimneys are installed by the customer, or a
general contractor who may not know how to set a proper chimney height in relation to the structure
(refer to illustration 1). Kit chimneys also can be affected by outside temperature more so than a masonry
chimney, so installation of a "chase" (a structure built around a kit chimney that is insulated) may be
needed in extreme cold climates.
A newer house, or a house that has been reinsulated, had siding, or insulated windows
installed could cause difficulties as well. A chimney must pull a certain amount of air out of a structure
in order to provide sufficient combustion air into the stove. In order for the chimney to remove air from
the structure, ample "make up air" must be allowed into the structure to compensate for a "tight house". A
structure that is well insulated and sealed may not allow this airflow to happen. A basement installation
can have similar effect as the basement will always have a slightly lower air pressure than the upper
floors of the house due to "stack effect" this is caused by warmer air rising inside the structure much as
it does in a chimney, as the air is bottled up in the top of the house it is leaving the lower areas of
the structure, air usually does not leak into a basement freely enough to compensate. Installation of an
outside air source should correct this. The outside air intake should be run in as short and direct a
route as possible, and should be installed with pipe no smaller than the opening on the stove.
Most masonry chimneys and kit chimneys have a port or door which makes cleaning of the
flue easier. These clean out doors should be sealed as air tight as possible when using the stove, the
reason for this is that in order to pull air through the stove, a chimney should not have any other
openings where air could be pulled into the flue other than through the stove, if air is being pulled into
the flue for anywhere other than through the stove, the amount of available air for the fire is being
reduced causing a bad burn, And more importantly, the air being pulled in through the leak is much
colder than the air moving through the stove, this will cause a cooling effect in the chimney and
will allow creosote to build up more rapidly in the flue.
Most importantly, the flue size must be at least the same diameter as the exhaust
opening on the stove, it can be bigger, but it cannot be smaller.