This is a question that a lot of homeowners ask us when we are at their homes. Should you close vents in unused rooms?

There is an assumption that closing vents in unused rooms will redirect heat within the home. Or that shutting the vents saves energy. This is not entirely true. While shutting off vents can increase airflow elsewhere in the HVAC duct system, it’s not as much as you may think.

Closing off vents, however, is extremely easy to do. Reach up towards the vent in the ceiling and turn the knob clockwise. That closes off round ceiling registers. Have floor or wall-mounted registers instead? Most of those square vents have a thin piece of metal you can close them with that moves the damper inside of the register.

Given how easy it is for the homeowner to close a vent, there is a common misconception that doing so can be beneficial to the AC or the Heating in the home.

Back to increasing airflow, say you have 10 registers in your home, and the total CFM of your HVAC system is 1400cfm. That means, on average, each register puts out 140cfm. Closing off one of those vents will redistribute that air across your ductwork system. You are increasing each vent to 155cfm on average. This is not enough of an increase to make a noticeable difference within the area of the home that doesn’t have a vent closed.

By closing off the vent in the unused room, you did change the airflow in the home. But you also caused several problems that you weren’t aware of.

First, you stopped conditioning the unused space 

This doesn’t seem like it has a significant impact, but having a room in your home within the building envelope and not being fed by your home HVAC system creates a more considerable energy loss than having air go into that space. In the winter, that room will get colder than usual. That cold will absorb heat through the walls of your home and slowly pull the heat out. In the summertime, that room will be hot and radiate within the house towards the areas you are continuing to cool.

Second, you’ve decreased the life of your fan

Closing off vents will also increase the pressure in the ductwork system of the home. This increase in pressure in the ductwork puts extra strain on the fan motor. This additional strain on the motor will cause it to wear more quickly and decrease your fan’s lifespan. Without a working fan to move the air, your system won’t work at all.

Third, you can create air leaks

The increased pressure in the ductwork from closing vents can damage weak connections in your ductwork. Creating air leaks in your ductwork means that you’re putting air in places it’s not designed to be, behind walls, under floors, or even in your attic. You are lessening the effectiveness of your HVAC system.

Summary

In closing, should you close vents in unused rooms? The answer is no. Keeping all of your vents open is the most efficient means of operating your HVAC system in your home. This allows you to have less repair and maintenance costs and energy savings compared to closed vents.

If you found this information useful, you can read more energy-saving articles in our Blog. Also, our Online Energy Audit is the easiest way to find more energy-saving methods in your home. Calculating the annual energy savings for insulation, HVAC, windows, and more.