Air Handling Unit

An air handling unit (AHU) is the central device that manages a building's mechanical ventilation system. A typical residential AHU contains supply and exhaust fans, air filters, and a heat recovery cell, all housed in an insulated cabinet. The unit draws in fresh outdoor air, filters it, recovers heat from the outgoing exhaust air, and distributes conditioned air through the duct system to living spaces.

The air handling unit is the heart of the home's ventilation system and directly affects indoor air quality, energy efficiency, and occupant comfort. A well-maintained AHU ensures adequate fresh air supply, removes pollutants and excess moisture, and recovers up to 90 percent of the heat from exhaust air. Modern units also include automatic controls that adjust ventilation rates based on humidity, CO2 levels, or time schedules.

Regular maintenance of the AHU is essential: filters should be replaced one to two times per year, the heat recovery cell cleaned twice a year, fans inspected for dust buildup and bearing wear, and condensate drains checked for blockages. Most homeowners can perform basic filter changes themselves, while the more thorough annual service is best handled by a ventilation professional.

Signs that your AHU needs attention include increased noise from the fans, reduced airflow from vents, musty or stale odors, elevated indoor humidity, or a noticeable increase in heating costs. The typical service life of a residential AHU is 15 to 25 years, after which replacement with a modern, more efficient unit is usually recommended.