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When it’s hot outside, your air conditioner has to work extra hard to keep your home at a comfortable temperature. During this time, you could find water droplets on your vents. 

It doesn’t necessarily mean that your AC unit is experiencing problems, but you should strive to find a solution. If moisture issues in the home are not identified and resolved, it can result in water damage, mildew, mold, and wood rot. 

Before we can tackle this issue, we need to answer the question: “What causes AC vents to sweat?” In this article, we will investigate why it happens, what could be causing it, and how you can fix the problem.  

Question - What causes AC vents to sweat

The Science Behind Condensation

When warm, moist air touches a cold surface, water droplets collect. This is known as condensation. You can see the same effect occur on your can of Coke on a hot day. 

If the supply vents for your HVAC system are sweating, it’s producing condensation. This is a telltale sign that the vent is ice cold, and is surrounded by humid air. 

The temperature of the cold surface needs to be lower than the dew point of the water vapor in the air for condensation to take place. The air also has to be holding a lot of water vapor, to begin with.

Deducing the Problem

When your AC vents are sweating there are one of two problems occurring:

  1. The supply vent temperature is too low. 
  2. The air is too humid. 

The solutions consist of either: 

  1. Increasing the temperature of the vent 
  2. Lowering the humidity in the air.

But how can you determine which solution to use? 

Measure the relative humidity and the supply vent temperature to find the dew point. There are websites that can calculate it for you. Once the reason for the sweating is discovered, steps can be taken to fix it.

Finding a Solution

Now that you know what is causing the problem, we need to decide how to address it. Does the temperature or the humidity level need to change?  This isn’t a simple answer; it depends on each individual and their preferences.  

A balance needs to be held and that balance has been conveniently provided by the Air Conditioning Contractors of America (ACCA). They recommend that temperature and relative humidity create a recipe for a dew point of 55 degrees Fahrenheit. That’s the key to sweat-free vents!

Let’s break it down for you.

Relative Humidity/Temperature:        

  • 42/80
  • 45/78
  • 50/75
  • 55/72
  • 63/68

Although it could be as simple as turning up or down your thermostat settings, sometimes getting this balance right needs expert intervention.

If Your Humidity is Too High

Most homes are leaky and let in the humidity from outside. Increasing your insulation and keeping doors and windows shut can reduce how much humid air seeps inside.

But even parts of your HVAC system can work against you. Ventilation systems like range hoods, driers, and bathroom fans will exchange indoor air with outdoor air. Energy recovery ventilators bring in less outdoor air than heat recovery ventilators, but ultimately, you will need a dehumidifier. 

Even houses with no leaks can have humidity problems due to an improperly sized AC. If your AC is too large for your home, it will run less and therefore remove less moisture. Again, in this situation, using a dehumidifier is the only method to keep vents from sweating.

If Your Vents are Too Cold

Some sources on the internet falsely claim that low refrigerant levels will cause vents to become wet. But this is completely untrue. 

When the refrigerant level is too low, the unit will freeze up and not be able to adequately cool. As a result of a frozen coil, the unit may begin to sweat, but never the vents.

Again, many sources also claim that reduced air flow or low air pressure is to blame, but we disagree. Vents will not sweat if the airflow is reduced. Sweating vents aren’t a side effect of clogged air filters or any other air pressure fluctuation.

It is possible for the vent to sweat if the air in the ducts is far too chilly. Occasionally, this is the result of a duct detaching and entering the house. Another possible explanation is that the ductwork is not properly sealed, allowing air from the attic to enter the house. Because of this, the vent begins to sweat because hot and cold air is mingling together.

If Your AC Needs Repair in Tampa Bay

When your AC vents sweat, and you can’t figure out why, call the experts! Our certified heating and cooling professionals will diagnose the problem. 

Although it’s less common, sweating vents can be a signal of an inefficient or improperly installed HVAC system. Sometimes, the compressor isn’t working right, or the ductwork needs to be better insulated. 

No matter what causes the condensation, if you wait to fix wet vents it can lead to bigger, more costly problems down the road. Make the safe choice and contact Action Air Conditioning to help you figure out what is causing your AC vents to sweat.