Should You Close Vents in Unused Rooms During Summer? An Experienced HVAC Professional Explains

​This seemingly smart summer habit could be harming your HVAC system. With another record-setting summer underway and AC units working around the clock, many of us are looking for ways to cut down on our electricity bills. 

While closing vents in individual rooms or spaces might seem like a reasonable way to save money this summer, it’s actually not quite that simple. Despite what you might have heard, HVAC professionals say that closing vents in unused rooms is not an effective cost-saving measure. In fact, it might be doing more harm than good to your HVAC system. 
Should You Close AC Vents In Unused Rooms In Summer?
“No, you should never close vents in individual rooms,” says Brad Martin, Field Service Manager for Boer Brothers Heating & Cooling in Chapel Hill, North Carolina. 
HVAC systems are designed to maintain a specific and balanced airflow known as CFM, or cubic feet per minute, throughout a home. Closing vents can increase pressure in the ductwork, potentially causing leaks or damage to the system. As a result, the system will not work properly or efficiently.
What Role Do Vents Play In Heating And Cooling A Home?     
Vents act as exit and entry points for warm and/or cool air to lower or raise the temperature in your house. As the return removes the cool or hot air, Martin says, the supply vents replace this air with the opposite of what it is removing. 
In most homes, the furnace (forced air) and air conditioner (central air) utilize the same vents. Proper air flow is essential to the function of both systems. 
What Are The Risks Of Closing Vents In Unused Rooms?
It might help to think of your HVAC system like your body’s cardiovascular system, and a closed vent like a blocked artery.  
“Closing vents in the individual rooms can cause the static pressure of the system to rise, causing issues like your blower motor failing, causing the compressor to fail,” Martin explains. “When individual vents are closed, the air still travels down that duct. Once it travels down the duct it has nowhere to go and then puts positive pressure back on the system.” 
Are There Any Energy Savings From Closing Vents In Unused Rooms During Summer?
Closing vents in individual rooms will not help your cooling costs but actually hurt your system. 
“Closing vents puts a strain on the system, which in turn causes the system to work harder,” Martin says. “HVAC systems are designed for a certain CFM, so when the system’s vents are closed, the air that is still traveling through the ducts puts pressure on the system. This causes both the motor and compressor to get hot. When mechanical parts get hot, they pull higher amperage causing electricity bills to be higher and not perform at top energy efficiency.” 
The Correct Way To Adjust Air Flow To Different Rooms 
Instead of closing individual vents during the summer, Marin recommends installing (or adjusting) butterfly dampers at the main duct line. These dampers act as a block at the main duct trunk line, causing your system to function like there isn’t a vent in that particular room at all. Unless you’re experienced working with HVAC systems, it’s best to enlist a local HVAC technician to handle this for you.
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