September 1st, 2016

Why Closing Air Vents can Do More Harm Than Good


Many people are under the impression that they can save money by closing their air vents in the rooms that they don’t use. But the truth is that it can actually cost them money. Let’s look at some of the things that can happen when you close your air vents.

Cause Problems With Your Blower

Depending on the kind of blower your air conditioner has, it can cause issues with your blower.

  • PSC Blower – When you have a permanent split capacitor or PSC blower, your blower will slow down when you have closed vents. This is because it cannot overcome the additional pressure that’s been put on it. It means that your system becomes ‘deprived of oxygen’.
  • ECM Blower – When you have an electronically commutated motor or ECM blower, this blower is able to adjust the speed to different conditions. When you have closed air vents, it is going to ramp up its speed so that it’s overcoming the additional pressure. This means that your energy bills will be higher.

How closing the air vents can damage an HVAC System

We have looked at how closing the air vents can affect your motor. But how will it hurt your system? Well, because PSC blowers slow down if your vents are closed, there is less air that’s being delivered over things like:

  • Your AC’s evaporator coil. This is the part in the AC which cools your air. When there is low airflow, your coil becomes too cold. This sometimes can make it freeze up. How closing air vents can hurt your HVAC system. Eventually, the liquid refrigerant will flow into your compressor and destroy it.
  • The heat exchanger on your furnace – This is what heats your air. When there is low airflow, your heat exchanger is going to overheat and may even crack.

If the parts aren’t covered under a warranty, you are going to have a costly bill since it’s better to replace your furnace or your AC since it’s a better option than replacing the expensive parts.

Other problems that closing vents cause

We have covered the biggest problem you’ll run into when you close your vents, which is a system that’s damaged. But there are also a few essential issues that closing your vents can cause

  • Issues with comfort – When you are closing up your vents, less iar will be delivered by your PSC blower. This means that your home won’t be as warm or cool.
  • Increased leakage from ducts – On the average, 20-30% of the air that is blowing through homes is lost because of leaks in air ducts. This means that you are paying anywhere from 20-30% more in bills than you should.

Closing the vents will worsen the problem with leakage since the additional pressure will force additional air from those leaks. A good analogy is jumping up and down on an air mattress that is leaking. The mattress already was losing air. But with the extra pressure on it, it’s losing more air.


As you can see, it’s a lot better if you are leaving your vents open even when you aren’t using a certain room. Otherwise you might find that you have costly bills and that you are paying out much more than if you had left them open in the first place.

Need Help? Talk to An Expert!

Our goal is to help educate our HVAC customers in the Port Charlotte and Charlotte County, Florida area about energy and home comfort issues (specific to HVAC, Heating and Air Conditioning systems).

If you are contemplating having your air conditioning repaired, Contact Dales Heating and Air Conditioning by calling (941) 629-1712 or by filling out our secure Contact Form.