Should I leave my interior doors open or closed when running my AC?

Cooling your home can be expensive, especially in a hot climate. Some months it seems like the air conditioner runs more than it doesn’t, making the sheer thought of opening your utility bill horrifying. People have devised a number of theories on how they can save money on air conditioning costs, but no theory is as pervasive as keeping interior doors shut.  

The theory is that if you shut doors to rooms you’re not using, you won’t have to cool them, saving you money. Unfortunately, this well-meaning wives’ tale will cost more and can create other indoor air problems.

A modern air conditioning system is carefully balanced as a whole. When you close down one part of the system, you’re not making the other parts stronger. On the contrary, you are disrupting the system’s operation. Not only will this force the system to work harder and potentially damage it, but your indoor air quality will also suffer significantly as your air conditioner tries to compensate for the sudden air imbalance.

So, to answer the million-dollar question: it is best to keep the interior doors open when your AC is running. Why? For starters, it allows better airflow and minimizes the pressure problems inside. Leaving the interior doors open can also make it easier for your AC to cool your home evenly, using less energy.

What Happens Behind Closed Doors

If you have a typically installed air conditioner unit with a central air return, shutting doors is one of the worst things you can do. (It’s right up there with closing vents and beating your outside unit with a sledgehammer.) When you shut a door, the air still blowing out of the vent builds in the room, pressurizing it. At the same time, the return is making an extra effort to suck in enough air to cool the entire house (not just the rooms with open doors).

The positively pressurized cool air behind the door is looking for a way out, and it eventually finds its way through cracks in walls, behind the trim, and around windows. The return is still trying to take in air, despite cool air flowing outside from the closed bedroom, and takes it from anywhere it can find it. This often results in negative pressure in the part of the living area that’s still open to the return, and outdoor air rushes into cracks and crannies.

As this cycle continues through the summer, you may notice increasing humidity, your indoor air quality sinking, and no real improvement in your power bill. Because so much outside air is pulled into your home, allergens, mold colonies, and other outdoor pollutants can build up inside. Only when you finally balance the pressure by opening up those closed-off rooms will your air conditioner be able to clear the air and cool your house at peak efficiency.

The Benefits of Keeping Your Interior Doors Open While Your AC is Running

Let us explore the many benefits of keeping your interior doors open while running your AC system and its impact on your home’s comfort and efficiency:

• Improved comfort. You will enjoy a more uniform and comfortable indoor environment when your interior doors are open. When you leave the doors inside open, you allow the air to flow freely between rooms, eliminating the trapped or stuffy air in certain areas. You will also create some sense of cohesion so everyone can enjoy consistent comfort throughout.
• Improved air circulation. Keeping interior doors open is your best option if you want better airflow inside. Opening the doors allows the cool air from your air conditioner to circulate more freely and reach all the areas of your home. This setup also prevents stagnant air so that you can enjoy a fresher environment.
• Energy efficiency. Opening interior doors is recommended to balance the air pressure inside your home. When doors inside are closed, pressure differentials are created. This causes your AC to work harder to ensure a steady airflow. Also, keeping the doors open can minimize the strain on your HVAC system. This translates to better energy efficiency and substantial savings.
• Enhanced air quality. When your interior doors are kept open, there is better ventilation and air exchange. This also helps minimize indoor air pollutants such as allergens, dust, and volatile organic compounds (VOCs). And since keeping the doors inside open promotes fresher air, you will enjoy a healthier living environment. This is especially beneficial if you or a family member suffers from allergies or other respiratory conditions.
• Less HVAC Strain. If you close your doors inside while your AC is running, you will create pressure imbalances inside. This can cause your HVAC system to work harder to ensure adequate airflow. However, when doors are open inside, you can alleviate this strain on the HVAC system, significantly reducing the possibility of premature wear and tear. Keeping the doors open also extends the lifespan of your system and reduces the need for costly repairs or replacements.

The Pressure of High Utility Bills

Closing doors inside is a recipe for financial disaster, but you can do plenty of things to help keep utility bills down. Adding insulation, caulking around trim, and sealing visible cracks will help reduce the amount of air transmission from outside. Keeping your curtains and shades drawn during the hottest parts of the day will also help prevent heat from entering your home.

Air conditioners that sit out in the direct sun often run less efficiently because they have trouble getting rid of the heat from inside your home. Moving your air conditioner or installing a shade to keep it cool will help it work better. More permanent solutions like planting trees will help in the long run.

Turning on the fans in your home will increase indoor air circulation. Many people eventually discover they can raise their thermostats several degrees and remain just as comfortable without the air conditioner running as often. Fans are extremely cheap to run, especially compared to your air conditioning unit.

It can be tempting to slam the doors and hope the cool air builds up in the areas where you want it, but the fact is that modern air conditioning units are designed as whole-house systems. So when you shut that door, you’re only making it much harder for your system to cool your home.

Wrapping Up: Interior Doors and Your AC

Keeping your doors inside open while running your AC is recommended if you want to enjoy the many benefits we have mentioned. While studies or statistics have not addressed this practice directly, the benefits it provides are supported by the basic principles of energy efficiency, temperature balance, and airflow. Consider this practice if you want to create a more comfortable and efficient home and optimize your system’s performance.

If your air conditioner is experiencing any issues, don’t hesitate to call Precision Air at 602-349-6922. Our NATE-certified technicians are available 24/7 to address any problems with your AC without charging weekend fees or trip charges. We’re here to help keep you cool and comfortable, no matter what.