Fireplace External Air Supply

External air intakes are used to bolster a fireplace s supply of air.

Fireplace external air supply.

However my particular problem is with a wood fired oven. A fireplace consumes vast amounts of air each minute as the fuel burns. In other words you need to be able to close off the exterior air supply and it must be configured to prevent burning material think coals popping off a burning log from entering the supply duct. The fireplace installer technician mentioned the possibility of adding an external air supply to the wood stove.

Modern wood heaters can be connected to an external air duct to secure the necessary combustion air. We have several resources to help. He advised against it though because in his experience this is only necessary for very new highly insulated homes. In those homes the fireplace would not be able to draw in enough new air through cracks and vents causing incomplete combustion underpressure and other undesirable outcomes.

In a sealed fireplace with combustion air supply this isn t an issue. An open fireplace in contrast can exhaust such a large volume of air that it could affect the operation of for example a conventional gas fired furnace or water heater. In addition to the chemical reactions between the fuel and the air there is expansion due to heat which pushes gases up the exhaust and draws in a correspondingly larger volume of air. It can easily be 250 to 350 cubic feet of air per minute.

Since the air consumption of a wood stove is so low the risk of reversal of a ducted combustion air supply outweighs any advantage gained by bringing air from outdoors. The fresh air vent in the hearth may be blocked or it may not be able to supply enough air to satisfy the appetite of the fire. The additional air to feed the fire must come from somewhere. Proper research prior to installation is the key to simplifying the process.

This air duct is supplied at the top by an air exhaust chimney. For masonry fireplaces the area of the exterior air passageway must be at least 6 square inches but not more than 55 square inches. Fireplace air vent installation can sometimes be difficult to figure out which air intake vent kit is right for you. Fireplaces especially wood burning fireplaces can consume a large amount of oxygen in a short amount of time and the normal vents traditionally installed are not always enough to supply the needed oxygen.