Why The Chimney Should Penetrate The Highest Heated Space; Supply Of Combustion Air - Enerzone Solution 2.3 Installation And Operation Manual

8.4.2 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 stove.
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 stove and into the room.
Even the finest stove will not work
well when connected to this chimney.

8.5 Supply of Combustion Air

In Canada, wood stoves are not required to have a supply of combustion air from outdoors (except
in mobile homes) because research has shown that these supplies do not give protection against
house depressurization and may fail to supply combustion air during windy weather. However, to
protect against the risk of smoke spillage due to house depressurization, a carbon monoxide
(CO) detector/alarm is required in the room in which the stove is installed. The CO detector will
provide warning if for any reason the wood stove fails to function correctly.
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