Supply Of Combustion Air - Drolet Deco Nano Owner's Manual

chimney and strong draft build quickly as the chimney flue warms up. Although they are common
in North America, chimneys that exit a house wall and run up outside can cause problems.
Figure 3: Good System Design
When it is cold outside, the warm air in the house is buoyant so it tends to rise. This creates
a slight pressure difference in the house. Called 'stack effect', it produces a slightly negative
pressure in the lower part of the house (compared to the outside) and a slightly positive pressure
zone in the high part of 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 in the lower
part of the house will compete against the desired upward flow in the chimney. This occurs for
the two following reasons:
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 in the lower part
of the house will draw cold air down the
chimney, through the stove and into the
room. Even the finest stove will not work
well when connected to this chimney.
6.6

Supply of Combustion Air

In Canada, wood stoves are not required to have a combustion air supply from outside, except
for mobile homes. Research has shown that outside air supply do not compensate for the
depressurization of the house and may not be sufficient to provide a supply of combustion air in
windy weather. However, to reduce the risks against smoke spillage due to house depressurization,
a carbon monoxide (CO) detector is required in the room where the stove is installed. The CO
detector will provide warning if for any reason the wood stove fails to function correctly.
Wood Stove - Owener's Manual -
Figure 4: Inferior System Design
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