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Don’t Close or Block HVAC Vents and Registers!

Don’t Close or Block HVAC Vents and Registers!

July 27, 2018

Dont Close Block Vents and Registers Fix It

You may think it’s a good idea to close or block HVAC vents to prevent conditioned air from entering an unused space- but think again.

While it’s understandable and makes sense to want to keep your precious conditioned air from entering certain spaces, it can cause major problems with your HVAC system. If you want HVAC “zones,” there are better ways to do it, such as installing dampers inside the ducts or switching over to ductless mini splits.

Whether you are purposefully or accidentally blocking HVAC vents, spend some time to go around your home and make sure they are all open and unobstructed.

Why You Shouldn’t Block HVAC Vents

There are two different types of vents in your forced air system: supply vents and return vents.

  • Supply vents supply the conditioned air (typically smaller).
  • Return vents pull air out of your indoor space (typically larger).

Return vents don’t have louvers. Supply vents have louvers or slats, allowing you to direct the airflow. They aren’t there to close off airflow.

Both vents need to be completely free and clear for your HVAC system to work safely and efficiently.

There are many reasons why you shouldn’t block HVAC vents and registers, including:

  • Pressure buildup and increased duct leaks
  • Condensation and mold growth
  • Frozen AC coils
  • Refrigerant leaks
  • Blower motor problems
  • Increased energy use
  • Comfort and humidity problems
  • Dead compressor
  • Cracked heat exchanger (potentially sending carbon monoxide into home)

No matter how many vents and registers are blocked, your HVAC system outputs the same amount of air and pressure. Since your HVAC system is specifically designed for a specific amount of airflow, by messing with the supplies and returns, you will only cause problems with excessive pressure in the system.

In addition to excessive pressure, your indoor air handler won’t get the proper airflow it needs to work properly. This can lead to coil and heat exchanger problems in winter and frozen coils and compressor problems in summer.


There are many reasons why you shouldn’t close, block, or obstruct any of the HVAC vents in your home. Now that you are convinced, follow these rules:

  • Don’t block the supply or return vents in your home, such as placing clothes over it to dry, closing the louvers, or placing furniture in front.
  • Make sure there is enough clearance around all of your vents and registers.
  • While vents may be unsightly, they are there for a reason. Go around your home and check under area rugs, behind furniture, and paintings. Someone may have covered them up.

If you have any questions or want HVAC zoning in your building, speak with the professional heating and cooling technicians at Fix-It 24/7.

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