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Central Florida’s Choice


Facemyer Air Conditioning and Heating Blog

This Common Piece of AC Advice Is Totally Wrong


We live in an information-packed society, where we can access a world of data from professionals with only a few keystrokes.

We can also access a world of rumor, hearsay, and urban legends with those same keystrokes, and telling apart legitimate information from “stuff somebody wrote on the internet” can be tricky.

The experts have a place to speak, but false information also has room to continue to propagate.

This battle of Expert vs. Unfounded Ideas often affect us in the HVAC world. Far too many pieces of incorrect advice about cooling and heating homes and how HVAC systems operate circulate around the internet and can appear as they’re coming from knowledgeable sources.

We can list numerous examples of erroneous “facts,” but in this post we’ll focus on one extremely common bit of AC advice that is utterly incorrect. Following it can lead to AC troubles, higher cooling costs, and even the need to call us for AC repair in Orlando, FL.

Here it is:

You can save money on your cooling costs by shutting the vents in unused rooms.

Here’s our answer:

No, you cannot. In fact, you may waste money and create other problems.

What’s the Story Here? 

We can understand why this piece of incorrect advice has immediately appeal. It sounds like it could be true. You think about the ductwork in your house that transports the cooled air from the AC to the rooms. The rooms vents have louvers in them that you could potentially use to shut the vent. Why wouldn’t closing the vents in an unoccupied room mean the AC would work less because it has fewer rooms to cool?

Let’s break it down:

  • The louvers in vents are designed to help direct air as it comes into a room. They don’t make much of an effective seal if closed all the way, since that isn’t what they’re supposed to do. 
  • Closing off any vents (or using objects to block them) doesn’t make the air conditioning system do any less work. The air conditioner’s blower and compressor don’t sense there are closed vents and therefore lower their capacity. They both continue to operate at the same power as they work to lower the temperature to the thermostat setting. Not as much cool air will get to the places to closed vents, but the AC is still generating the same amount of cooling.
  • Closed vents create an increase in pressure within the ventilation system that will make the HVAC system’s work more difficult. The blower is now working against pressure, and this strain will cause it to waste power. Instead of paying less to cool the house, you might end up paying more when vents are closed off.
  • The rise in pressure can cause damage to the rest of the HVAC system. One of the main causes of air leaks in ducts comes from pressure rising too high in the ventilation system. Blocked vents can also cause the AC to freeze over because the air pressure drop will lead to a decline in airflow over the evaporator coil, leaving it too cold from the refrigerant. 

There are many ways you can lower your summer cooling costs, but this isn’t one of them. If you want to control which rooms do or don’t receive cooling, ask our technicians about installing zone controls. 

Rely on Facemyer Air Conditioning and Heating: Exceeding Your Expectations With Comfort.

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