What's causing my duct work to pop when the furnace starts or stops? A popping noise is a typically sign of an under-sized duct design. It may have to do with greater air flow than the duct work is built for. Have a qualified company analyze your home's ventilation system for proper design and make necessary recommendations. Improper duct work layout can cause a variety of ventilation and air quality problems, including: loud banging noises higher energy bills lowered lifespan of the system uneven heating & cooling throughout your home damaged compressor in hotter months overheated unit in the cooler months In addition, if your ductwork is the wrong size you may have other concerns, such as leaky ducts and poor layout that restricts airflow. In humid climates this can cause mold growth within your ductwork. Back To Frequently Asked Questions