Does Shutting Furnace Vents Improve Energy Efficiency?

Ben Kissam
Written by Ben Kissam
Updated October 5, 2021
 opening/closing floor vent hear
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You may think closing furnace vents will help your system run better, but think again

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Logically, it makes sense that closing vents in unused rooms could be a good thing. If you’re not using those rooms, after all, why should you heat or cool them? What a good way to lower energy bills and even preserve your HVAC system, right?

Unfortunately, that isn’t the case. In fact, for those wondering if they should close vents in unused rooms, the answer is almost always a resounding “no.” Below, we explain why—plus what you should be doing instead.

Why You Shouldn’t Be Closing Vents in Unused Rooms

Conventional wisdom might suggest that closing vents could save you money on heating and cooling costs. Fewer rooms, less energy, right?

However, your home’s heating and cooling systems were designed with your home’s size in mind (which, if you’re building a home, is one reason you should make sure you figure out which size furnace you need). Even if you close the vents, the system still generates the same amount of hot or cold air. 

When you start closing vents, you essentially put more heat or cold air into less space than the system was designed to handle. This change can cause your HVAC system to overwork, resulting in higher energy bills and damage over time.

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5 Issues Caused by Closing Vents in Your Home

Closing vents is a simple mistake that could have big consequences.

1. Damaged Ductwork

When you close vents in unused rooms in your home, this air gets backed up, causing pressure to build up in your ducts. Over time, this can lead to holes, leaks, and other issues that require repairs. 

Along with regular furnace checkups, you should also get your ducts cleaned and inspected every three to five years.

2. More Wear and Tear on Your System

HVAC systems are typically rated to last 15 to 25 years. While you can replace parts to preserve the life of your unit, general wear and tear will eventually necessitate a total replacement by a local HVAC technician.

Closing vents in unused rooms can cause your system to overheat and increase wear and tear. Excess hot or cold air can damage parts of your system and can speed up the need for replacement.

3. Frozen or Overheated Coils

Evaporator coils absorb heat from the air in your home’s furnace, and the most common reason coils overheat or freeze is due to restricted airflow. Along with keeping your vents open in your home, you should also replace filters regularly to help prevent air from getting trapped in your system. (This can also reduce noise in your AC or heating vents.)

Over time, frozen or overheated coils can lead to serious downstream damage to your HVAC system.

4. Reduced Energy Efficiency

Lowering heating or cooling costs is the primary reason you might close vents in the first place. Unfortunately, you’re likely doing more harm than good in this regard (and might even be harming your health with all your green efforts). 

Because closed vents wear down your unit, any money you theoretically would save on cooling or heating will likely wind up going to paying a local HVAC repair person.

For savvy spenders and eco-conscious homeowners, zoned HVAC systems may be a good solution. Depending on your budget and home size, you can have a system that cools two, three, or even four areas of your home at a time.

5. Carbon Monoxide

The other issues mentioned above are definitely nuisances, but a carbon monoxide leak is a serious, potentially life-threatening matter. 

Closed vents put extra pressure on your heating system. This stress can cause the heat exchanger to crack, emitting dangerous carbon monoxide gas into the air. 

Regularly inspect carbon monoxide detectors in your home. If your detector goes off or you suspect there is an issue, leave your home and call 911 right away.

However, Partially Closing Vents May Be Okay

Fully closing vents isn’t recommended for all the reasons mentioned. However, partially closing them (50 to 75%) in rooms you aren’t using could help pump more warm or cool air into the rooms or areas that need it most. This measure prevents air from getting trapped and pressure from building up in your ductwork.

It’s best to close vents that are furthest away from your home’s HVAC system. The further downstream they are, the less likely your unit is to overheat or freeze.

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