Should Air Vents In A Basement Be Open Or Closed?

Basements are prone to the growth of mildew and mold, the buildup of dust, and sometimes unpleasant odors, all of which can lead to respiratory problems. So does this mean that vents should be left open to let in the fresh air, or is it fine if they remain closed? We consulted with experts to provide insight into what should be done.

You should close your basement air vents during the summer and open them during the winter.

Continue reading to find out more about opening and closing the vents in your basement, how many vents you should have, where they should be located, and what to do when the AC is on. Without further ado, let's get into it!

A closeup shot of a ventilation cap on a yellow painted wall with dark wooden plank on top. Should Air Vents In A Basement Be Open Or Closed

When To Close And Open The Vents In Your Basement

The first thought in your mind as soon as summer sets in would be to open the vents in your basement to keep the house cool and to close them to keep your house warm during winter. However, the opposite is actually true.

Close Your Vents In Summer

You are better off closing your vents during summer, and instead, let your HVAC do the work. This is because it helps control the temperatures to the desired level and significantly reduces your energy bills. When your vents are open, your HVAC will need to do more work, causing the bill to go higher.

But also don't forget that you need to maintain a good flow of air in your basement. Thus, it's a good idea to open the vents every day or so.

If you keep them shut all the time, your basement will end up being damp, creating conditions that allow mold and mildew to thrive, which could damage your wood surfaces or even discolor them.

You may also want to install a dehumidifier to help combat the growth of mold.

How To Maximize Your Benefits When You Close The Vents

While you will benefit by saving your power bills when you close your vents during summer, you need to ensure the following are in good working condition:


Check and make sure your vents are properly shut; they should not leak any air. If they do, it will be a challenge to control the temperatures in your home, and also, you will not reap the benefits from lower energy costs.

As seen above, your HVAC will work harder to lower the temperature if the vents let in a lot of air.

Air Coils

As soon as temperatures begin to drop and there is low airflow because your vents are closed, your AC coils could end up being frozen. That is why they need regular maintenance to prevent this from happening.

Open Your Vents During Winter

The most reasonable thing to do during winter is to close your vents. However, did you know you should open them instead? Since hot air rises, when you open the vents, the basement and other rooms in the house will be warm. But if you shut them, the basement will remain cold.

Furthermore, if you close your vents, your HVAC system may end up working too hard to heat the basement, causing damage to it.

That notwithstanding, if the vents do not bring in airflow, the air pressure will increase, also causing damage to your ducts. Do not forget, you will also save on your utility bills.

As you open your vents during winter to save on energy, it would be a good idea to repair all air leaks in your basement and the rest of the house. This is because the air leaks will prevent your HVAC from successfully controlling the temperatures in your basement and your home as a whole.

Therefore, check your crawlspace, windows, doors, plumbing, or ductwork and fix any air leaks you find. For example, you could seal the cracks by adding caulk to doors and windows or weather-stripping your windows.

Where Do Basement Vents Go?

Depending on how your home and cooling and heating system are constructed, the vents in your basement can be located in several places, some of which include the floor, ceiling, under the window, and in the outer walls.

The Floor

To keep your basement continuously warm, heat ducts can be extended downward to the floor level. These blow warm air into the room. However, for the room to be warm enough, the air return vent should also be at the floor level but on the opposite side of the heat duct.

With this type of arrangement, the vent returns the air back to the heat duct to be heated again, and the cycle continues. This prevents cold air from stagnating near the floor.

The Ceiling

Since hot air rises and the cold air sinks, ceiling vents are predisposed to create a cooling effect in your basement, especially during summer.

Under The Window

The advantage of dryer vents under or on the side of a window is that other than having enough light entering your basement, you will still receive fresh air.

The Outer Wall

Having a heating vent on the outer wall of your basement is advantageous because it will reduce the condensation of moisture that takes place when the weather is cold outside.

How Many Vents Should Be In A Basement?

The number of vents in each room of your home, including your basement, depends on their size. Principally, a 100 square foot room should have two vents. This means if your basement is larger than 100 square feet, you will require more than two vents, and if it is smaller, then one will suffice.

There are two types of vents that you can have in your basement, and each has its function as shown below:

Ceiling Air Vent

Supply Air Vents

These vents remove air from your basement and into your cooling and heating system through the ducts and out of the vents again. You can actually feel the conditioned air coming out of them. They have slats that can be adjusted to blow air in the direction you wish.

Cold air return vent Inside residencial home, air vent on a white wall with carpet.

Air Return Vents

These do the exact opposite of supply vents. They draw in air into the system, which is conditioned, and then pumped back into your basement through the supply vents.

You can find out if it's a return air vent by holding a piece of paper in front of it; the paper will get sucked inwards into the vent.

Air return vents are larger than supply vents. They don’t have any slats because the air goes into the duct and not out of it, and that is why you will not feel the air being blown out from them. They are normally found on the ceiling, floor, or at the base of a wall.

Which Vents Should Be Open In Summer?

Ideally, none of the vents in your basement should be open during summer. As shown above, the reason for this is to save your energy bills.

But you can't keep them shut for long. Open them intermittently to prevent the growth of mold and mildew; if you close them for a day or two, also open them for an equal amount of time.

Also, by opening the air return vent occasionally, the air is pulled in, reducing the pressure on your HVAC.

Should Basement Vents Be Closed When AC Is On?

No, the vents should not be closed even when the AC is on. In fact, if you close them, the air conditioner could end up getting damaged because it is forced to work harder as a result of the air pressure that builds up in the basement. Subsequently, your energy bills will go up.

Should You Close Basement Vents In Winter?

As we have discussed above, the experts reiterate that opening the vents during winter will make it warmer than if it were closed.

Furthermore, opening your vents will prevent your HVAC from working harder and getting damaged.

Air vent or ventilation system in the basement. Should Air Vents In A Basement Be Open Or Closed

In Closing

Vents are very important for bringing fresh air into your basement. This prevents the build-up of mold, dust, and unpleasant odors, which can cause respiratory problems.

It is also important to open the vents during summer and close them during winter. By doing this, you save a lot on your energy costs.

Depending on the design of your house, your vents can be placed in strategic places for constant airflow in your basement. Therefore, they are usually found on the outer walls of your house, under the window, in the ceiling, and some on the floor.

Check out these posts below on how to air out your basement and cool it without an AC:

Should You Air Out Basement?

How To Cool Basement Without AC?

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