Open or Closed: Should You Shut Interior Doors When Running HVAC?

Open or Closed: Should You Shut Interior Doors When Running HVAC?Have you ever closed a door to a room while the HVAC system is running and noticed how, in spite of there being a supply vent in the room, it becomes uncomfortably colder or warmer? Why is that? The short answer is that your HVAC system isn’t designed to work that way. But read on, and we’ll explain a little more about why you shouldn’t close interior doors in your home while the HVAC system is running.

What Closing Doors and Vents Does

It seems logical that closing the doors to and vents in rooms not in use would mean the A/C or heating system wouldn’t have to condition as much air and you could thereby save money on your utility bill. The fact is, however, an HVAC system is designed to condition air throughout the house, not just room by room. The system draws in return air through vents — sometimes there are several about the house, but in some cases there might just be one for the entire house. The return air is filtered, heated or cooled, then distributed through the supply vents in each room. Closing doors and vents interrupts that process by creating a pressure imbalance.

What Happens When Pressure is Not in Balance

When you close the door to a room and the HVAC is on, pressure builds up, forcing the conditioned air out minute cracks around the door, the windows and in walls. That means you’re wasting energy and driving up your bills. When you close off the vents, you are likely forcing that conditioned air to leak through the ductwork in an unconditioned space — again, a waste of energy and money.

Another factor is that by closing doors, the main system creates a negative pressure and starts drawing in unfiltered return air from the outdoors — like the chimney, furnace, or water heater flue. That air is likely polluted with dirt, dust, humidity and even carbon monoxide.

As you can see, closing interior doors just isn’t a great idea. For more information on how your HVAC system works, contact CCAC of South Texas.

Our goal is to help educate our customers in Corpus Christi, Texas about energy and home comfort issues (specific to HVAC systems). For more information about your HVAC system, download our free Home Comfort Guide or call us at 361-678-2495.  

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    David Mathewst David Mathews is the owner of CCAC Air Conditioning and Heating. A Corpus Christi native... More »