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Osburn Matrix Inbuilt Installation and Operation Manual
9.6 THE RELATIONSHIP BETWEEN THE FLUE SYSTEM AND THE HOUSE
Because the flue 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
wood inbuilt, slow kindling of new fires, and smoke roll‐out when the door is opened for loading.
9.6.1 WHY THE FLUE SYSTEM 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
inbuilt. 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
inbuilt and into the room. Even the finest
wood inbuilt will not work well when
connected to this flue system.
9.7 AIR QUALITY IN THE HOUSE
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 wood inbuilt is installed. The CO
detector will provide warning if for any reason the wood inbuilt fails to function correctly.
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