Twists and turns in ducts, along with long spans of ductwork, conspire to restrict air flow. While some parts of your house seem cozy, others may suffer from a lack of heated or cooled air from your HVAC system.

The problem is usually worse in older homes with ducts that weren’t designed to handle modern heating and cooling systems.

How booster fans help

Booster fans are add-ons that help move air through ducts. While inline duct and register booster fans will not cure underlying defects, they can “boost” air flow, thus increasing the amount of cold and warm air that ultimately makes it to a room.

First, check the basics

Inspect your HVAC system for problems that might be contributing to airflow and efficiency problems. Dirty filters, peeling duct tape, and obstructed air returns all can decrease HVAC performance.

Types of HVAC booster fans

Register booster fans are the most economical and simplest to install. These plug-and-play units replace your existing floor, wall, or ceiling register. They mount flush to the surface, plug into the wall outlet, and feature a modest internal fan that goes on and off when the HVAC system kicks in. Some feature a thermostat and multi-speed fan.

Prices range from $30 for a basic unit up to $80 for those with digital thermostats, multi-speed fans, and remote control.

Inline duct fans are cylindrical fans that replace a section of ductwork. That means your HVAC ducting must be exposed to work on it. Though some units simply plug in, most are hardwired and require a relay back to the furnace that tells the unit when to switch on. Installation may require an electrician.

Inline duct fans are quieter than register booster fans, but you’ll have to know the size and shape of your existing ductwork so you can pick the right-sized unit.
 
Count on paying $30 to $200 for an inline booster fan, plus a couple hundred dollars for the electrician.

A word of caution from a pro

“The biggest challenge is the return air — getting the stale air from the second or third floor back down to the furnace to be heated or cooled and redistributed,” explains Tom Hutchinson, president of Hutchinson Plumbing Heating Cooling.

“While cost-effective, we don’t see that booster fans provide a whole lot of success in remedying the problem,” explains Hutchinson. “The best solution is adding returns or installing a thermostatically controlled zone system.”