Excessive HVAC Condensation and How to Fix It
Have you noticed condensation on your air vents? Wondering why there’s condensation on your windows? Learn why it’s happening and what you can do about it.
By Anne Fonda
Your HVAC system naturally produces condensation during the cooling (and sometimes heating) process. When you run your AC system, it removes moisture from the air while it cools. This moisture condenses into water and moves into the external condensate drain line. The condensate line, condensate pan, and condensate drain all play a part in removing normal condensation from your home.
The problem arrives when the condensation becomes excessive. Learn all about HVAC condensation, high humidity, and how to prevent and fix condensation problems.
What is condensation?
Condensation is the conversion of water vapor to water droplets. Water droplets form on a cold surface when it comes in contact with warm or humid air. A couple of everyday examples - think of a cold beverage on a hot summer day—condensation forms on the outside of the glass, bottle, or can.
Similarly, on a humid summer morning, condensation on the outside of your windows and patio door may form. This condensation is harmless. However, condensation on the inside of your home can indicate a problem.
Indoor condensation - When to worry
Indoor condensation on your windows, walls, or air vents that is persistent means you have high indoor humidity levels. You need to get to the root of the problem and fix it before it causes big problems.
Occasional condensation after a hot shower may mean you need a better bathroom exhaust fan, which is an easy fix. Likewise, condensation on your toilet tank just means it’s time to close the windows and turn on the air conditioner.
This article will discuss HVAC condensation as well as condensation due to high humidity, and how to fix the issue.
What causes condensation in HVAC systems?
Before we get into the causes, let’s tell you what the signs of excessive condensation in your HVAC system look and smell like.
Signs of excessive HVAC condensation
- Exposed ductwork in your attic, crawlspace, or basement may look like the AC ducts are sweating.
- Condensation on AC vents.
- There’s a musty smell when the AC is running.
- Your HVAC air filter is damp.
- There’s a puddle on the floor by the indoor unit.
Causes of HVAC condensation
- Leaky ductwork lets moist humid air into the air duct system.
- Inadequate ductwork insulation - Remember what happens when warm air meets a cold surface?
- Poor ventilation can allow humidity levels to climb.
- A clogged or dirty air filter can hamper proper airflow.
- Clogged condensate drain lines or drain pan problems can lead to stagnant water and overflow.
- A frozen evaporator coil can create a lot of condensation as it thaws, potentially overwhelming the drainage system.
- High humidity levels can cause condensation on your ductwork, on your windows, and your walls.
Problems resulting from HVAC condensation
Excessive HVAC condensation along with high humidity can cause a variety of problems, including:
Damage to HVAC components
Excess moisture in your HVAC system can cause early corrosion or rusting of the drain pan or air vents.
Indoor air quality issues
High humidity and HVAC condensation on ductwork can cause indoor air quality (IAQ) issues. You may also notice that your HVAC system smells musty when the air conditioning turns on.
Mold and mildew growth
How can condensation in HVAC systems lead to mold growth? Simple - by providing a warm, moist environment. Mold and mildew thrive in dark, damp, and warm areas. Learn more about how to protect your HVAC system from mold growth.
Water damage
Much of your HVAC ductwork is hidden from sight. That means you may not know there is condensation on the air ducts until you have wet drywall or a wet ceiling. Constant dripping can result in puddling which can do serious damage to your ceiling, walls, insulation, flooring, furniture, and appliances.
Increased energy consumption
How does condensation affect HVAC performance? Negatively. Clogged filters, leaky ducts, and poorly insulated ductwork can all cause your HVAC system to work harder, leading to increased energy usage and decreased efficiency.
How to fix HVAC condensation
If you’re searching for how to stop condensation on air vents, this is the part you’ve been waiting for. To resolve the excessive condensation issue in your HVAC system and restore comfort to your home, you need to fix the HVAC issues and control the humidity levels.
With the help of an HVAC professional, do the following.
- Duct sealing or fixing leaky air ducts. This includes different methods for sealing exposed ductwork as opposed to sealing hidden ductwork.
- Insulate ductwork.
- Schedule regular HVAC maintenance and inspections.
- Clean and unclog condensate drain lines.
- Improve ventilation.
- Install a whole-house dehumidifier if you live in a humid area.
- Replace old, oversized, or inefficient HVAC systems.
A note about oversized systems - while your system may have been sized correctly when it was installed if you have recently completed any improvements in or on your home to insulate it better, it could reduce the HVAC load in the house. That could now cause the unit to be oversized where it was initially sized correctly. You’ll want to talk to an HVAC professional about changing out your system to a smaller size.
By taking care of problems in your ductwork system, performing regular maintenance, and maintaining proper humidity levels, you can prevent HVAC condensation problems in the future. You can also increase your comfort.
Consult with an HVAC expert
If you have high humidity in your home, condensation around air vents, or a musty smell when the AC turns on, you need expert help from a trained HVAC professional. Consult with your local Trane Comfort Specialist to get to the bottom of the issue.
After a home visit and reviewing your HVAC system, they’ll recommend a permanent fix to your condensation issues.
Anne Fonda, Content Writer
A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.
She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism.
When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.
Expert review by Kimberly Sexton, Senior Systems Engineer
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