Should I Leave Interior Doors Open Or Closed When The AC Is On?

Many people think that they can simply shut the doors to their bedrooms, laundry room, home office and other interior rooms and they’ll be able to save a little money on heating and cooling bills. Unfortunately, while this practice is fairly common, the homeowner is setting in motion an inefficient and, even, dangerous situation.

Today’s HVAC systems move a great deal of air during the normal process of heating and cooling a home, and proper air flow is crucial to energy efficiency as well as personal comfort. When one or more interior doors is closed, air flow is interrupted and serious problems can arise.

For example, when a bedroom door is closed, the HVAC system will still be putting air into the room, but the air is trapped and pressure begins to build up. Of course, the air that you have paid so much to condition is then forced to find a way to escape. It will be forced back out of the house, following any escape path it can find.

Unfortunately, for every cubic foot of conditioned air that is forced out of a room, an equal amount of unconditioned air will be drawn back into the home from outdoors. The more interior doors that are closed, the more conditioned air will be forced out with more hot or cold air from outside being brought into the home. In fact, the draw of unconditioned air can increase by 300 to 900 percent depending on how many doors are closed. This not only dramatically increases utility bills, but indoor comfort decreases and health problems can occur.

As the HVAC system requires large amounts of air to replace the air that is forced out from the pressure of closed doors, outdoor air finds its way in through the easiest path. This is typically a reverse air flow from the furnace flue, fireplace flue or chimney. As this air comes into the home, it brings outdoor pollutants, increased risk of carbon monoxide poisoning and a greater risk of mold and mildew due to higher humidity.

So in short, we recommend keeping your doors open or only shutting them for as short of a period as possible when your HVAC unit is running.

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