Treacherous & High Beam, you're both right.
There is no question that air evacuation caused by chimney updraft can cause cold, dry outdoor air to be drawn in through cracks and other openings in the house's shell, adversely affecting heating efficiency and the comfort of the occupants.
What originally gave birth to the Washington State legislation, however, were health issues that can result in tightly built houses, where the same air evacuation by the chimney can overcome the less-powerful outflow from other combustion devices in the household, such as gas furnaces and water heaters, and drag the colorless, odorless and poisonous exhaust from those flues back down into the breathing space.
The wording of the law as eventually enacted leaves room for interpretation by the state's individual code authorities. Most of them have chosen to require outside air in all new wood stove & fireplace installations, one reason being it can be difficult to judge the relative leakiness of a given home. I'm told that King County, where BG lives, only requires outside air in newly constructed houses.
There is no question that air evacuation caused by chimney updraft can cause cold, dry outdoor air to be drawn in through cracks and other openings in the house's shell, adversely affecting heating efficiency and the comfort of the occupants.
What originally gave birth to the Washington State legislation, however, were health issues that can result in tightly built houses, where the same air evacuation by the chimney can overcome the less-powerful outflow from other combustion devices in the household, such as gas furnaces and water heaters, and drag the colorless, odorless and poisonous exhaust from those flues back down into the breathing space.
The wording of the law as eventually enacted leaves room for interpretation by the state's individual code authorities. Most of them have chosen to require outside air in all new wood stove & fireplace installations, one reason being it can be difficult to judge the relative leakiness of a given home. I'm told that King County, where BG lives, only requires outside air in newly constructed houses.