In many homes, the HVAC vents have fins that can be adjusted with a sliding switch. These fins can be used to direct airflow at a particular angle, but if you push the switch all the way to the side, they can be used to close off the vent entirely. You might think that you can save energy by closing off the vents in unused rooms, but that’s not the case -- not only can this cost you more on your utility bills, but it can also cost you more in repairs over the long haul.
A Counterproductive Strategy
It’s not an unreasonable hypothesis -- if cooled or heated air isn’t escaping through the vents into one or two rooms, it should take less energy to produce the amount of treated air needed for the remaining rooms. But HVAC systems just aren’t designed to work that way.
An HVAC system is somewhat like the respiratory system in the human body -- in order for it to work as it’s designed, there must be adequate airflow. Most systems are calibrated in such a way that a change in airflow can choke out energy efficiency and put excess strain on system components.
Closing vents increases the pressure in your ductwork, and that pressure increase backs all the way up to your HVAC systems, forcing them to work harder. This causes the same types of problems as having a dirty air filter -- your furnace or air conditioner uses more energy to produce the same level of treated air, driving up your monthly bills. It also stresses out fans, motors, and other equipment, reducing maintenance intervals and leading to more frequent repairs.
Excessive duct pressure also creates another problem -- duct leaks. Weak spots in your ductwork can turn into open gaps, allowing treated air to escape and forcing your system to work even harder.
Get In the Zone
Fortunately, the concept behind closing vents in unused rooms can be safely put to work with the right HVAC equipment. Certain systems called “zone HVAC systems” give you unprecedented control over which rooms receive treated air. Using a more sophisticated interface than an ordinary thermostat, zone systems allow you to assign different temperatures to different zones, which can be as small as a single room.
This is especially handy when you want to save energy by treating a room to a higher or lower temperature without shutting off the flow of air to those rooms completely. While there’s no need for an unoccupied room to receive the same level of comfort, a total lack of HVAC can lead to mold and humidity damage in the summer or frozen pipes in the winter.
If you’re interested in learning more about HVAC zone control and what it would take to upgrade your home system, get in touch with your local HVAC professionals.