Why The Chimney Should Penetrate The Highest Heated Space - Drolet Austral II DB03031 Installation And Operation Manual

Austral II Installation and Operation Manual
Good System Design Inferior System Design
Inside chimneys are preferred because even Outside chimneys are a problem
when no fire is burning, there is normally because when no fire burns they will go
upward flow in the system. into cold backdraft if the stove is
installed low in the house.

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.
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