Should the interior doors be left open or closed while a home is heating or cooling?
This question may not seem very important to some, because people don’t give much thought about whether they should leave their interior doors open or closed when an HVAC system is on. Surprisingly, studies and research have revealed that the simple act of closing the interior door can trigger serious health and safety problems in the house, not to mention affect the comfort of the occupants in a big way too. What’s more, this does not bode well for energy efficiency. Thus, it is always recommended to keep the interior doors of a home open while the HVAC system is being used, be it for heating or cooling.
The reason why it is necessary to keep these doors open is because the fans in an air conditioning or furnace system typically move large volumes of air inside the house, about 1000 to 2000 cubic feet of air every sixty seconds. By closing the door, one would be directly blocking the pathway of the air, and this gives rise to numerous problems. When an interior door is closed, the air flow through the HVAC system and into the room is reduced significantly. Thus, the air that is put into the room by the system gets trapped, which in turn pressurizes the room.
Due to this increased pressure, the cool or conditioned air is forced out of the room through any opening possible. To fill up the vacuum created after the conditioned air is forcefully eliminated from the room, an equal amount of outside air is drawn in. Thus, the more doors you close, the greater the rate of the outside air being drawn into the house. In fact, the rate can increase from 300 to 900 percent if too many interior doors are left closed.
Because of this, the energy efficiency feature of the HVAC system would no longer be valid and energy bills would go up while increasing the discomfort inside the house. Thus, it is advisable to always leave your interior doors open as long as possible when heating or cooling your house.