Which Vents Should Be Open In Summer?

The basic law of convection tells us that hot air is light while cold air is denser. Therefore, during natural convection, hot air rises while cold air sinks. 

To this end, you must seasonally adjust your air vents to correspond with the changing outdoor temperatures. For instance, you should make it easier for hot indoor air to escape the home and reenter the AC by placing return vents close to the ceiling. The opposite is true for winter. 

However, that’s just the first part. Read on to learn which vents should be open in the summer and which ones should be shut and how to close your vents and adjust your dampers to control airflow in the home. 

Should All HVAC Air Vents be Open?

Ideally, yes. You should always keep your air vents open if you want a healthy air conditioner, a comfortable home, and reasonable power bills.

Moreover, closing the air vents can cause issues such as frozen condenser coils. A frozen condenser coil, ultimately destroying the AC outdoor unit. It costs $3,500 or more to replace the outdoor unit. 

That said, though, keeping the vents open all the time only works perfectly if the vents are located correctly. Otherwise, keeping them open can only worsen your energy inefficiency issues by allowing conditioned air to escape from the house.

Additionally, closing some vents may prevent stale air from leaving the house, thus reversing your air conditioning gains. 

As a result, it makes the most sense to shut some vents while keeping others open, depending on the year. 

Why you should Switch your Vents Seasonally

Seasonal switching is the best approach because it allows you to capitalize on Charles’s Law on the relationship between temperature and density in gases.

The law states that hot air is less dense because the same mass of air acquires a larger volume as it expands. Thus, hot air is less dense than standard-temperature air.

However, the opposite is true for colder-than-standard air. For this reason, hot rises to the ceiling while cold air settles to the floor. 

Therefore, indoor air generally rises during the summer while cold air from the air conditioner falls. Opening or closing various air vents in the home to capitalize on the air movements can help you keep your home more comfortable without necessarily spending more on energy. 

When to Switch your Vents

The best time to switch the vents is on the first day of heating or cooling, though you can always do it a few days earlier, so you don’t forget.

The bottom line is that the vents should be appropriately adjusted before turning on the air conditioner or furnace for the summer or winter. 

Should Vents be Open or Closed in the Summer?

Ideally, you want the vents open in the summer, as we’ve already mentioned. However, it depends on the vent location. Leaving open vents that would allow conditioned air to escape the house doesnt make much sense, does it? 

To this end, it’s best to leave open all the vents that promote maximum airflow and energy utilization while closing those that don’t. 

Which Vents Should be Open in the Summer?

Your lower return air vents should be closed in the summer while the upper vents remain open. However, the roles are switched in winter; keep the lower vents open and the upper vents closed. 

Al high vents should be open during the summer. The reason is that hot air rises, and summer is a hot season. So, you need a way to let the hot indoor air naturally escape from the house while retaining cold, conditioned air. 

So, begin by closing all ceiling vents. Then assess the wall vents too. First, you want to close all the wall vents to the ceiling. This shouldn’t be a big problem as return vents are typically very high, close to the ceiling, or very low, close to the floor. 

Should Upper Vents be Open or Closed? 

Yes, upper return vents should be open to allow the rising warm air out of the house. Remember that cold air is dense and thus remains close to the floor. Therefore, you don’t have to worry about losing the conditioned air via the upper vents. 

However, be careful not to mistake supply air vents for return air vents. Return vents bring hot air back into the air conditioner while supply air provides your rooms with cool, conditioned air. 

Should Low Vents Be Open or Closed in the Summer?

Low return air vents should be closed for the summer season. The reason is that cold air is denser than standard-temperature air. Thus, cold air falls naturally to around the floor level. 

Now imagine if the vents on or near the floor level are open! All the cold, conditioned air would flow out of the house back into the AC. This negates all the air conditioning gains while adding to energy bills. Closing the lower vents helps to retain cold air. 

Which Return Vents Should be Open in the Summer?

The upper return vents should be open throughout the summer. This allows the rising warm air to exit the house, promoting the indoor cooling process while enhancing energy efficiency. It also allows the naturally rising airborne particles to exit the house. 

You can distinguish return vents from supply vents by holding a piece of paper against the vent grille. Return vents will “attract” the paper, while a supply vent will “repel” it. 

Should Foundation Vents Be Open in the Summer?

You should keep foundation vents open during the summer as they draw fresh air critical in preventing moisture build-up. 

However, don’t confuse foundation vents for basement vents. Foundation vents are typically rectangular metal vents in the crawlspace. They often have a small lever that allows you to pull the vent closed or open. Meanwhile, basement vents are found in the basement. 

Allowing the free flow of air throughout the crawlspace during the summer helps prevent mold, mildew, and other moisture-related issues. However, keep it completely shut in winter. 

Should Basement Air Vents be Open or Closed in the Summer?

Generally, you should switch basement vents open and closed intermittently during the summer to keep the area cool and comfortable without losing too much cold air. For instance, you should consider closing half the vents while leaving the others open for two days and then switching.  

Alternatively, if you have just one vent in the basement, keep it open during the day and closed at night for the summer. 

The bottom line is that you neither want to keep the basement vents open or closed permanently as both extremes present massive challenges. So, you can even open the vents for a few hours during the day and then close them. The choice is yours. 

How to Close Return Air Vents

Modern return air vents have a lever on the side of the vent that you can move back and forth to open or close the vent. Alternatively, you can purchase vent blockers off Amazon and install them over the vent opening. 

However, avoid DIY vent blockers as they rarely completely seal the vent. Moreover, you don’t want to damage the surfaces around the vent. 

How to Adjust the HVAC System Damper

You can also adjust the HVAC damper instead of closing the vent altogether. Adjusting the position of the damper allows you to partially block airflow into or out of the air conditioner to control the heating and cooling process. 

  1. Begin by identifying where the vent branches. This is most often in the basement, crawlspace, or attic. 
  2. You will find the damper leaver attached to the duct at the branching. 
  3. Turn the lever opposite to the duct direction to close the damper or in the direction of the duct to open it. 
  4. You can also adjust the damper so that it’s partially closed. 

What about the Supply Vent/Supply Vents?

Supply vents should also remain open in the summer to bring cool, conditioned air into the room. However, it comes down to the vent location.

Lower supply vents should be closed as leaving them open provides an escape route for cool, conditioned air. Meanwhile, upper supply vents should remain open for the summer as there’s no risk of losing cold air. 

Other Tips to Keep Your Home Cool in the Summer

  • Adjust the dampers
  • Use your ceiling fans wisely
  • Maintain proper air pressure
  • Ensure proper air conditioning system maintenance
  • Check for and fix air vent leaks


Does Closing Air Vents Redirect Air?

Yes, closing air vents can redirect air, but rarely where you want it. The common misconception is that closing the vents in one room redirects conditioned air to the other rooms. Unfortunately, it isn’t so simple. Instead, the first that happens when you close some vents is pressure build-up in the ducts, often leading to air leaks. 

Should Air Vents be High or Low?

Ideally, return air vents should be high (on or close to the ceiling), while supply air vents should be low, close to, or on the floor. This enables natural indoor circulation of warm and cold air through convection, enhancing indoor air conditions while reducing air conditioning costs.  

Should you Close the Heat Vents in the Summer?

In the short term, yes. Closing the heat vents during the summer will help you save on energy bills during the year’s hottest months. However, don’t close the vents permanently. Otherwise, you may cause air blockages that damage the ductwork or AC. Instead, we recommend opening them for a few hours daily or several hours every two days. 

Which Direction should Return Vents Face?

All high return vents should face down so that the rising hot air naturally rises into the ductwork. Floor return vents usually point upward to capture the hot air. However, all floor vents should be closed during the summer, as we’ve mentioned, to avoid losing cold, conditioned air. 


Generally, it would help if you kept HVAC vents open for the better part of the summer season. However, since air density changes as the air temperature with season changes, it makes even more sense to close lower return vents in the summer and only keep the upper return vents open.

Meanwhile, keep the lower supply vents open and the upper supply vents closed. Finally, speak to a professional HVAC technician if you still feel lost.