Exhaust ventilation removes stale air, moisture, and contaminants from indoor spaces by mechanically extracting air to the outdoors. This system creates negative pressure inside the building, drawing fresh outside air through infiltration and intentional openings. Exhaust ventilation is commonly used in kitchens, bathrooms, and laundries where moisture and odors require rapid removal.
Technical Details
Exhaust fans typically operate at 50 to 400 CFM (cubic feet per minute) depending on room size and application. Bathroom exhaust fans generally require 50-110 CFM per ASHRAE 62.2 standards, while kitchen hoods may exceed 300 CFM. Ductwork must be properly sized and sealed to minimize energy loss and maintain system efficiency.
Practical Applications
Exhaust ventilation works best in homes with adequate air leakage or supplemental fresh air inlets. In well-sealed modern buildings, this approach can create excessive negative pressure, potentially drawing in unfiltered outside air or creating backdrafting issues in combustion appliances. Combining exhaust ventilation with supply ventilation or heat recovery systems provides better indoor air quality and energy performance.