Is it OK to Close Air Vents in Your House to Redirect Airflow?

We hear the question a lot. Is it OK to close vents in my house?

The quick answer is, Yes, it is OK to close air vents. But it’s not recommended, especially if you close multiple vents all of the way and keep them closed.

And there are caveats. How many? For how long? Why? Is there a better solution?

This article will explore these questions, address some of the situations in which closing a vent causes more harm than good, and the underlying issues of closed vents.

Consequences of Closing Air Vents

Closing an air vent (or two) may solve problems. For instance, if you’re dumping heat into a room that no one is using, it makes sense to cut off that room’s source of heat. After all, isn’t it a waste of money to heat something that no one can enjoy?

If you close the vent for that room, that forces the air - at least some of it - to another room that might be a little chilly.

But let us consider traffic patterns. After all, your ducts are very similar to roads. The highway is the supply plenum coming out of the top. Then, surface roads such as High Street are the trunk lines. So you take the largest volume of air and split it in two directions. Off of the main streets, you have neighborhood streets. Those neighborhood streets are the supply runs that have the dampers in them.

If you start closing off all of the neighborhood streets, the traffic gets congested. If you try to turn down one road, and it’s closed, then try to turn onto another road, and that one is closed, you can understand what happens to the traffic on the main road. Is it getting stuck? Is it going down another neighborhood road? Is it where it’s trying to go?

So now there’s more traffic in that neighborhood. And the main street is jammed with traffic. It’s the same with airflow.

The main detriment is that it causes high static pressure. High static pressure can lead to other issues. It puts stress on the blower motor because it’s trying to move air that isn’t moving as freely.

High static pressure also means you’re not getting enough return air to the furnace. The furnace has to overwork to compensate for that. It’s like putting a mask on your face. You can breathe through that mask. High static pressure is like running a marathon while wearing a mask. You can breathe, but it’s much easier to breathe without the mask.

Closing Vents to Create Zoning

I don’t even know that I would say that it’s bad to close vents. Most modern homes have dampers, which are located inside the duct. They’re designed to adjust airflow. Even if you close a damper, you’re not closing 100% of the air. It’s not an airtight seal. Air will go around that metal.

You can create zones upstairs and downstairs to combat the heat of summer and the cold of winter. Heat rises. Zones can be set up for a variety of reasons, but the main thing they do is to create a different temperature from the rest of the house.

So in the winter, homeowners can close the upstairs vents halfway, and let the heat from downstairs rise to the second story. And vice versa in the summer; if you want all of the cold air going upstairs, you close the downstairs vents.

Most people close dampers because they want more airflow to a specific area. Empty nesters, for example. It’s not that big a deal if you close dampers in rooms that are used only three weekends a year, when family or friends come to visit. Close the damper halfway or three quarters so a little bit of air is going in there.

If your home is built for zoning, you might have two trunks coming off of the front of the furnace, and two off of the back. One of the trunks feeds upstairs, and the others feed downstairs. Two trunks are controlled by the thermostat upstairs, the others are controlled by the thermostat downstairs. When these open, these close. That is the traditional zoned system.

Do You Know How Your HVAC System Works?

Most people don’t understand the way their HVAC works. Part of our job is educating people. I ask people “How much do you know about your system?” More often than not, the answer is “I don’t know anything.”

They go to their thermostat and set it at whatever temperature is comfortable for them, and that’s the extent of their knowledge. You can be living in a house and have a zoned system and never actually know how or why it’s set up the way it is.

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The house might have belonged to empty nesters. Once the children moved out, they never used two rooms, so they closed the vents or dampers. If you don’t realize that, you might feel that two rooms are too cold (or too hot) because that’s the way the house is. So you use a space heater. It may never occur to the homeowner to go down and figure out their ductwork, to figure out which vents go to which room. Most people don’t even know what a damper is.

That’s one of the questions the salespeople always ask: “Do you have hot and cold spots?” If half of their house is closed off, I ask why. Maybe it’s a true zoned system.

Using Automatic Ductwork Dampers

If you want to take a step up in technology, you can have automatic dampers installed on your ducts. You need a smart thermostat to control automatic dampers. They require communicating thermostats.

If you take a house that wasn’t built for zoning and you want to control the airflow, you would take round dampers and put them in the supply lines. You’d have to isolate them to figure out which go upstairs, and which go downstairs. The more zoning you’re trying to do, the more dampers you’ll need. More dampers mean more wiring, more work that has to be done, so that can be a large investment.

You can have the automatic dampers when you set up something called a “dump zone,” a room that nobody uses, such as an attic or crawl space. If the system is getting too much static pressure, the dampers automatically open into the dump zone.

You can zone a system with automatic dampers, and have a thermostat upstairs and a thermostat downstairs, and then you can have two different climate-controlled sections.

Closing Your Air Vents Isn’t Addressing the Bigger Problem

Your HVAC system is designed to move a certain amount of conditioned air, to heat and cool the entire home.

Opening and closing your vents all of the time might be in vain because you might not have the right-sized air conditioner or furnace for your home. You might not have the right capacity of a blower motor to move the air. The ductwork could be mis-sized.

If you feel like you need to close vents, you have an airflow issue, and the best solution may not be adjusting vents. Perhaps your system wasn’t designed correctly to begin with. You could have poor airflow because you fell victim to a sloppy HVAC contractor. According to energy.gov, 90% of HVAC systems are incorrectly sized.

If you’re opening and closing vents and the process is still not doing what it should, it probably is time to consult with an HVAC professional who will give you an evaluation of what’s going on with your system.

If you want to upgrade and get a unit that can deal more effectively with uneven temperatures, you can look into multi-stage equipment, modulating gas valves, two-stage gas valves, variable-speed outdoor units, and two-stage outdoor units. They can deliver a smaller volume of air and run longer while using less energy. This will help solve the issue of restricted airflow, and the hot and cold air will have more time to mix.

Read more: HVAC Buyer’s Guide

Will Closing Ductwork Dampers or Air Vents Lower Your Fuel Bill?

No. It’s the same amount of energy being used to air through the ducts. It may be being directed to different areas, or, like the traffic analogy, it might be backed up. Your blower wheel in your furnace may have a difficult time moving air, but the power used to push it remains the same.

Managing Air Vents and Zones in Columbus, Ohio

If we consider the main HVAC to represent your organs (thermostat = brain, furnace = heart), your ductwork is the circulatory system that connects everything and allows the organs to do their job.

Vents and dampers can be closed for a reason. You know your home best, and you know where some additional airflow could make a difference. Your comfort level can increase with some alterations.

But it's up to you - and possibly an HVAC expert - to weigh the risks. And there aren’t easy answers. The comfort level in your home is a complicated equation that includes ducts, a furnace, an air conditioner, and accessories (humidifiers, dehumidifiers, etc.).

The first step you can take is simple: Be aware, be informed, and talk to your HVAC partner when it comes time for either maintenance visits or to replace a major component of your system. You won’t be sorry that you did.

Need to get in touch with an HVAC contractor? Are you in Columbus, Ohio, or Central Ohio? Contact us to get started.