HVAC Questions: Should You Leave Interior Doors Open?

HVAC Questions: Should You Leave Interior Doors Open?Are closed interior doors standing in the way of optimum indoor comfort in your home? One of the most important functions of your HVAC system is consistent circulation of cool or warm air to all parts of the house. Unfortunately, closing interior doors can interfere with the process and actually make the entire house less comfortable–well as increasing monthly operating costs.

Here are some reasons why keeping doors open (as much as practicality and privacy permit) supports better cooling and heating performance in the home:

The system was designed for open doors.

When your HVAC system is installed, several important specifications such as the output of the system blower as well as the size of ductwork were calculated on the assumption that interior doors remain open. If certain doors are closed, inconsistent cooling and heating often results–too much in some areas of the home, too little in others– and overall indoor comfort will be compromised.

Central systems require both supply and return airflow.

The supply duct system conveys cooled or heated air to the individual room. Return ducts, meanwhile, convey conditioned air back to the central A/C or furnace to be cooled or heated again. Many residences are designed with air supply vents in every room but only one central return duct, typically located in a common area such as a hallway.

If the door to an interior room is closed, conditioned air entering that room through the supply vent cannot reach the central return intake and flow back to the air conditioner or furnace. This deficit disrupts proper airflow volume throughout the entire house, affecting cooling and heating consistency in other rooms, as well as increasing energy consumption and operating costs.


For houses where interior room doors must be shut for some reason, alternatives include airflow grates installed in the doors to allow supply air volume to flow out of the room and have a path to the central return duct. This supports proper air balance while still preserving privacy.

For professional advice on HVAC issues relating to closing interior doors, ask the professionals at Cool Power.

Our goal is to help educate our customers in Hauppauge, New York and the Long Island area about energy and home comfort issues (specific to HVAC systems). For more information about home comfort and other HVAC topics, download our free Home Comfort Guide or call us at 631-292-0629.