Can I Locate My Basement Cold Air Return on an Outside Wall?

Basement Cold-Air Return

• The main cold-air return trunk typically runs between two joists in the basement ceiling and connects to the HVAC unit. Air output and air input must balance, and the amount of air draw the HVAC unit requires depends on the size of the unit, the configuration and length of the ductwork and the how many rooms the unit services. If there is no other place in a room to install the vent so that it connects with the return-air trunk, you can install it on an outside wall.

Damper

• In many homes, the HVAC system is in the basement. Return-air vents nearest the HVAC system receive the strongest draw of air, and the draw dissipates the farther away a vent is from the unit. When you install a return-air vent in a room in the basement, the HVAC unit may draw most of the air it needs from that vent, weakening the draw from vents upstairs. To reduce air imbalance, always install a register with a manual damper on a basement cold-air vent. Adjust the damper to reduce the draw in the basement vent if you find that air circulation is not adequate in upstairs rooms. Signs of inadequate air circulation can include higher humidity and foggy and frosty windows.

Alternative

• Because the air draw in a basement can be so strong, you might be able to install a passive air vent in a room in the basement if it's adjacent to a room or a hall with a cold-air vent. For example, if you have a cold-air return in the ceiling of a basement hallway, when the HVAC unit turns on, it will draw the air from that hallway to feed the blower. If you want to vent a bedroom adjacent to the hallway, you can install a passive vent in the interior bedroom wall, next to the hallway. As long as the bedroom has heating and air ducts, when the HVAC unit turns on, it will draw air through the passive vent and into the hallway cold-air return.

Considerations

• One of the biggest reasons for not running cold-air returns on outside walls is the inability to insulate the stud space that contains the vent, which reduces the home’s energy efficiency. An interior wall is always preferable to an outside wall, but if that’s the only feasible location for the vent, you can install it there. The best practice is to consult an HVAC expert who can look at your home's unit and offer advice on where to install the vent.