Should I Leave Interior Doors Open Or Closed During Heating And Cooling?

We may be biased, but we think that air conditioning is one of the best inventions of the modern era. It keeps you cool and comfortable, no matter how high the temperatures get during our Los Angeles summers. If you’re looking for ways to get the most out of your cooling system, those articulating partitions (AKA doors) throughout your home may pique your interest. So, should you leave doors open or closed when the air conditioning is running? 

Keep Doors Open While HVAC is Running For Best Results

Here’s a basic principle of HVAC that’s helpful in answering this question: the air in your home is continuously recirculating through your HVAC system. Keeping the path of airflow completely open will ensure your unit operates at its best. Closing doorways will restrict the movement of airflow, limiting the path air can travel to the undercut of the door and between any joints. When doors are open, air can travel more freely throughout your home. 

Here’s another way to think about it. Think about blowing up a balloon for a birthday party. You start by holding the balloon’s opening to your lips with your fingers. When the distance between your two fingers is wider, the air from your mouth will fill the balloon quickly and smoothly. The tighter you hold the balloon’s opening, it becomes more difficult to inflate the balloon if you’re blowing with the same force as before. 

In general, keeping doors open will improve airflow through your house during air conditioning.

When To Keep Doors Shut During Air Conditioning

There are some cases where you should keep doors shut during air conditioning. 

One scenario is a room that you do not want or need air conditioning in, such as a closet. Keeping these doors closed during air conditioning will limit the airflow to them. That can save you a small amount of money in energy bills, but keep in mind that sometimes you want cool air to circulate in these spaces. For one, air conditioning can help with humidity control. If the space you don’t need cooling in has a supply air vent, consider shutting off the vent which will help redirect airflow to other spaces. Do this with caution, as closing an air vent changes the balance of airflow in your system, and could cause other performance problems. 

Another scenario where you should keep your doors shut while the air conditioner is operating is during sleeping hours. Keeping doors closed when you are asleep is an important fire safety precaution. According to Underwriters Laboratories, 50% of house fires happen between 11pm at 7am. A closed door can reduce fire growth, limit damage to your home, keep temperatures down, and most importantly, save your life in the event you become trapped. So, make sure you close before you doze.

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Editor’s note: this blog was originally published in May 2015 and has been updated for content and accuracy.