How to Improve HVAC Airflow in Rooms Furthest From the Heating Unit


In most cases, poorly designed or inadequate ductwork leads to poor airflow in the room furthest from the heating unit. Ideally, the best solution involves calculating heat gain and heat loss for that particular room and re-installing ductwork professionally designed to deliver the correct airflow. Unfortunately, this is usually prohibitively expensive and best performed by an experienced HVAC contractor. However, most homeowners can follow a few basic steps to improve the comfort in rooms furthest from the heating unit.

Things You'll Need

  • Furnace Tape or Duct Tape
  • Silicone Sealant
  • Duct-mounted or External Booster Fan
  • Locate the heating unit and inspect any exposed ductwork leading to the room(s) with poor airflow. Check for poor or leaky seals and any obvious gaps that allow air to escape. Seal smaller gaps with silicone sealant, larger gaps with furnace/duct tape.

  • Inspect any exposed flex duct for kinks or bends which could restrict airflow. If you find any, straighten them out.

  • Locate the registers in your home and determine which can be closed without compromising your comfort. For example, rooms with multiple registers may achieve adequate comfort with only one open. Closing registers on a main floor can help force more airflow to rooms upstairs. Close any registers in rooms that are often unused.

  • Install a booster fan. If you have minimal or no exposed ductwork or are not confident in your ability to install a duct-mounted fan, buy a booster fan designed to sit on top of the register or one that replaces the register cover. These models typically plug into a wall outlet. If you prefer a less visible solution, purchase a booster fan that can be installed directly in the ductwork following the instructions provided by the manufacturer.

Tips & Warnings

  • With new or recently constructed homes, you may be entitled to warranty repair to your heating and cooling duct system at no charge.
  • If the described steps don't yield satisfactory results, there may be a physical obstruction in the ductwork causing the lack of airflow (such as construction debris in newer-built homes). Hiring a duct cleaning service may alleviate this problem.
  • You may need to hire a trusted HVAC technician to assess your system and provide professionally executed solutions such as installing a zoned system or retrofitting dampers into the ductwork to redirect the flow of air.
  • Use caution when installing a duct-mounted booster fan. Altering your HVAC system or attempting to wire a vent booster into your air handler's control may void any remaining warranty.

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  • Tim Perry, Sales Manager; HVAC distributor; Indianapolis, IN
  • Ask the Builder
  • Photo Credit register close up image by Ray Kasprzak from
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