Many years ago, because of the prairie enforcement of the gas code provision that you had to supply fresh air to a furnace, an inventor in Alberta began marketing the Hoyme damper. This is a motorized damper that closes off that combustion air duct from the outdoors that dumps cold air into the basement and that most homeowners simply close off because it is too cold. This separate source of air became necessary for furnaces and their chimneys because we began making energy efficient houses that didn't supply enough air for the furnace burner through cold air drafts. Now if you have a modern sealed combustion unit, you don't need this because the furnace has its own air supply provided directly to the burner.
In the East is has only been in the last few years that inspectors have begun to enforce the provisions in the gas code requiring adequate air for a furnace or boiler that uses household air for the chimney. So basements are starting to get cold. The fact is that the Hoyme damper is widely available to the heating industry, it is just that installers and renovators don't know about it.
Why do you need this particular damper? It is a motorized damper that is tied into the thermostat of the furnace or boiler. When the thermostat calls for heat, the damper opens. In fact, the furnace can't even go on unless it is open. When the furnace goes off, it closes. In addition it is set up so that the fail safe position is open, maybe making a cold basement but assuring that the chimney won't be backdrafting dangerous gasses into the house. It is the only combustion air damper that I am aware of that is approved by the gas code.
If you install this damper, your furnace/chimney will have the combustion air it needs to work properly and you won't have a freezing cold basement because of that large open fresh air duct.
If you have a furnace or a boiler with a chimney, meaning that it is using the air from the basement for the burner unit, and you undertake a modern basement renovation -- you definitely need to install a combustion air duct. You might as well include the control damper at the same time.
"Hoyme Manufacturing"
4512 39th Street
Camrose, Alberta T4V 2N5
Toll Free: 800-661-7382