Living Smart: Does shutting furnace vents improve energy efficiency?
The Charlotte Observer, November 19, 2015. Image credit: Georges Grondin
Closing vents to a bedroom or bathroom that you’re not using seems like a sensible way to increase energy efficiency. With the door and vents shut, no heat should pump into the room, freeing your heating, ventilation and air conditioning system (HVAC) to heat the rest of your house. At first glance, there’s nothing fundamentally wrong with this idea: The forced air has to go somewhere, so why not redirect it rather than using it to heat rooms you don’t use as much? But a 2003 study by the Lawrence Berkley National Laboratory, cited by the Consumer Energy Center, found that “register closing led to increased energy use.”
Because the rooms in your home have cold-air returns as well as heating vents, shutting the vents doesn’t prevent air movement. Just like closing doors to prevent air flow, it interferes with your home’s energy efficiency. It creates pressure in the closed-off room, which causes the return duct to pull in cold air from any cracks in windows or doors.
In addition, the warm air still trying to push up through closed vents will start to leak out any ducts that aren’t sealed properly, or it will be forced back down into your basement or into floor cavities. So you’ll still be paying energy costs for heat, just in places you can’t use.