Specifications

Rocket 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.