The best defense against the stack effect is to carefully seal your homes against air leaks. Mechanical equipment can also cause negative pressure. Unbalanced air flows between the return and supply sides of a duct system may be caused by leaky or disconnected ducts, by blockage in the ducts or by closed interior house doors that block air flow between supply registers and returns. In a small or tightly built house, exhaust devices often cause the most powerful depressurization. Even a small fan can create potentially dangerous depressurization.
Leaky houses can have problems, too, if there are appliances with powerful fans.
These include downdraft ranges, new clothes dryers, attic or whole-house cooling fans, and central vacuum cleaners. Poor chimney design can also be a culprit. Chimneys should be sized to match the appliances they serve. In addition, interior chimneys provide better draft than exterior chimneys. Inc. All Oikos pages copyright 1996 - 2001, Iris Communications, Inc .