6 Air Supply in Conventional Houses The safest and most reliable supply of combustion air for a wood furnace is from the room in which it is installed. Room air is already preheated so it will not chill the fire, and its availability is not affected by wind pressures on the house. Unlike commonly expressed concerns, almost all tightly sealed new houses have enough natural leakage to provide a small amount of air needed by the furnace. The only case in which the furnace may not have adequate access to combustion air is if the operation of a powerful exhaust device (such as a kitchen range exhaust or air exchangers) causes the pressure in the house to become negative relative to outdoors.
If an air fresh air supply is installed through the wall of the house, its pressure can vary during windy weather. If there are changes in wood stove performance in windy weather, and particularly if smoke puffs from the furnace, the air duct should be disconnected from the stove to determine if it is the cause of the problem. In some windy conditions, negative pressure at the duct weather hood outside the house wall may draw hot exhaust gases from the furnace backwards through the duct to outdoors. Check the outdoor air duct for soot deposits when the full system is cleaned and inspected at least once each year. Additional combustion air can be provided following the following methods, provided that they satisfy chapter 4 of the CSA B365 standard for Canada : - Direct combustion air supply: Heating units requires specific certification to be connected directly with fresh air supply. Your furnace have been tested and is certified to be connected with direct combustion air.
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