One concern

One concern with exhaust ventilation systems is that -- along with fresh air -- they may draw in pollutants, including:

• Radon and molds from a crawlspace
• Dust from an attic
• Fumes from an attached garage
• Flue gases from a fireplace or fossil-fuel-fired water heater and furnace.

These pollutants are a particular concern when bath fans, range fans, and clothes dryers (which also depressurize the home while they operate) are run when an exhaust ventilation system is also operating.

Exhaust ventilation systems can also contribute to higher heating and cooling costs compared with energy recovery ventilation systems because exhaust systems do not temper or remove moisture from the make-up air before it enters the house