3 Nasty Consequences of Closing Air Vents in Unused Rooms

August 27, 2014

Everyone hates wasting money. 

That’s why some Kansas homeowners think, “Why bother cooling a room in my home I barely use? I’m going to shut the air vents so I don’t waste energy!” 
 
That sounds nice in theory. I mean, those vents blowing out air have little levers. So you should be able to use them, right?
 
But closing those vents can actually:

  • Make you uncomfortable in other parts of your home
  • Cost you money
  • Damage your heating/cooling system

We’ll explain why in this nifty article. 

How closing vents makes you uncomfortable

To understand why closing vents can make you uncomfortable, let’s back up for a second and describe how your cooling/heating system distributes air in your home: 

  1. The inside unit has a blower that pulls in air from your home via return grilles. 
  2. The AC or furnace cools or heats that air. 
  3. The blower pushes that cooled or heated air out the supply vents (the thing homeowners try to close).

Keep in mind: That blower is designed to push against air up to a maximum pressure. But if you close a vent, you’re increasing pressure in your duct system.
 
This causes the blower to keep running but at a lower speed. So now you have less air coming out supply vents in rooms you are using, leaving you uncomfortable.
 
In addition, the increased pressure in the duct system will make the blower work harder, decreasing its efficiency.

How closing vents increases air duct leaks and wastes money

You probably don’t know this, but your home’s air duct system probably leaks air.   

According to ENERGY STAR, the average home’s duct system loses 20-30% of the air blowing through it thanks to leaks.
 
Closing the vents increases pressure in your duct system, increasing the amount of air coming out of those leaks. It may even create more leaks. More duct leakage=money wasted and less comfort for you.
 
So closing supply vents in a leaky duct system is like jumping on a leaky air mattress.
 
(Side noteContact us to see if your air ducts need sealing so you can stop wasting money.)

How closing vents can damage your cooling or heating system

Remember how we said closing vents reduces airflow coming out your vents?

That means it also reduces the amount of air flowing over your:

  • Air conditioner’s evaporator coil (the part that cools the air)
  • Furnace’s heat exchanger (the part that heats the air)

That’s dangerous because now they’re not absorbing enough heat (in the case of the evaporator coil) or giving up enough heat (in the case of the heat exchanger). 
 
Here’s how that can cause costly damage:

  • In the summer, the AC’s evaporator coil will get too cold and turn into a block of ice (reducing airflow). Eventually liquid refrigerant flows back to the AC compressor, destroying it
  • In the winter, the furnace’s heat exchanger will get too hot, crack and possibly distribute poisonous carbon monoxide throughout your home. 

For the love of your system, don’t close air vents

Now we’re not saying closing one vent will cause all of these problems. But closing multiple vents and keeping them that way certainly can.

Have any other questions about the dos and don’ts of cooling and heating your home? 
 
Contact us with your questions. We’d love to help!

Santa Fe Air Conditioning and Heating serves the Kansas City area. For more information, contact us online. 


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