Why The Flue System Should Penetrate The Highest Heated Space; Installing The Flue Connector - Drolet ESCAPE 1800 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 flue system
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 flue system.
There are two reasons why the flue system
in the house at right will cold downdraught
when it is cold outside and there is no fire
burning in the wood fire. First, the flue
system 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 flue
system is shorter than the heated space of
the house, meaning the negative pressure
low in the house will pull outside air down
the flue system, through the wood fire and
into the room. Even the finest wood fire will
not work well when connected to this flue
system.

8.5 Installing the Flue Connector

The flue has been called 'the weak link' in the safety of wood heating systems because failure to
install the flue connector properly (which has been common in the past) can result in house fires.
The best flue is one that rises straight up from the wood fire to the base of the flue system with no
elbows. Straight assemblies are less likely to cause problems like smoke roll-out when the door is
open for loading. They are also more stable and easier to maintain than assemblies with elbows.
Horizontal runs of flue should be avoided where possible because they reduce flue system draft.
Figure 15: Best
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Figure 16: Acceptable Figure 17: Avoid
Installation and Operation Manual - Escape 1800