A movable flap inside ductwork that controls or balances airflow to different parts of the home.

A damper is a movable flap inside ductwork (or at a register) that can be opened or closed to control airflow. Dampers come in several types depending on purpose.

Common damper types

  • Balancing dampers — manually adjusted at install to even out airflow to different rooms
  • Zone control dampers — motorized, opened/closed by a zone control board based on each zone’s thermostat
  • Backdraft dampers — one-way flaps preventing reverse airflow (common at exterior wall penetrations)
  • Register dampers — manual adjustment on the supply register itself

Zoning systems

Multi-zone HVAC systems use motorized dampers to direct heating or cooling to different parts of the home based on demand. This is a great solution for multi-story homes, walkout basements, or homes with mixed sun exposure. Adds complexity (and cost) but dramatically improves comfort.

Related: Ductwork, Supply and Return, CFM.

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