Why Is My Ductwork Sweating or Dripping Water? Causes and Fixes

In coastal Oregon, we often have humid air as the marine layer moves in. Because it happens every year, your ductwork is under stress each time. For many of our customers, this is when their ductwork and vents sweat, creating problems.

Additionally, factors like poor duct insulation, uninsulated crawlspaces, and oversized ACs can increase the likelihood of this symptom. Is condensation a problem, and why does ductwork sweat? Let’s take a look at why exactly this happens.

What Causes Ductwork To Sweat?

While poor duct insulation, poorly insulated crawlspaces, and oversized ACs are the causes of ductwork sweating, the science behind it is called the ‘dew point.’

Dew Point in Plain Language

Put simply, the dew point is the temperature the air must cool to before it is completely saturated. Once it reaches this point, water starts to condense. It’s the same process that happens when droplets of water start to develop on the outside of a cold glass. Because your duct or vent is colder than the surrounding air, it gets to the dew point much quicker than it would in regular weather conditions.

Most Common Causes in Coastal Oregon Homes

If you’ve ever wondered, “Why is my ductwork dripping water?”, here are a few potential reasons why that’s happening.

Uninsulated or Under-Insulated Crawlspace Ducts

Even if crawlspace ducts were originally correctly insulated, salt air corrosion can break down the insulation. When the humid, hot air meets the cold ducts, the result is extra sweating. This is common in older Bandon homes, especially the ones that have crawlspaces without air-conditioning. Our team can fix this problem by re-wrapping ducts and repairing the vapor barrier.

Damaged Duct Insulation

Over time, duct insulation can become damaged by moisture, pests, or normal wear. This is especially a problem for homes along the Oregon Coast because of the salt air that constantly drifts inward throughout the seasons.

High Indoor Humidity

When your indoor humidity increases, it doesn’t take as much weather interference to reach the dew-point threshold. Cooking, showering, and doing laundry can easily increase the humidity levels in your home. Choosing to install a dehumidifier or exhaust fans is one of the best ways to reduce indoor humidity.

An Oversized AC That Short-Cycles

Oversized ACs reach the chosen temperature too quickly, so they shut off before running long enough to remove sufficient humidity for your comfort. While your home might feel cool, it will be more humid than it should be. To fix this, homeowners need a load calculation performed when they get an AC replacement.

Simple Checks Before Calling a Technician

Before you reach out for professional diagnostics, there are a few things you can do to troubleshoot your ductwork and AC vents that are sweating.

• Use Your Exhaust Fans: Whenever you shower or cook, run your exhaust fans during and for 15 minutes afterward. This helps to remove excess humidity and prevent duct sweating.
• Unblock Your Return Grilles: For proper airflow, the return grilles should never be blocked by furniture or rugs.
• Change the Thermostat: On heavy marine-layer days, duct sweating is more likely to happen. During these days, try raising your thermostat a few degrees, so the temperature difference between the ducts and the surrounding air is smaller.

If you are unable to solve the problem with these tips, you likely have a structural issue that needs to be fixed by a heating, ventilation, and air conditioning (HVAC) technician.

Fixes That Usually Require a Professional

While some problems can be addressed on your own, more complex cooling repairs and replacements must be handled by a professional. It’s the only way to ensure that the problem gets fixed quickly and on the first try.

• Duct Inspection and Insulation Repair: During our duct inspection, we’ll look for air leaks, vapor barrier issues, and signs that the insulation has failed. Then, we can recommend the best course of action.
• Indoor Air Quality (IAQ) Assessment: With this assessment, we can evaluate your home’s IAQ to determine if a dehumidifier, air purifier, or ventilation upgrade is necessary.
• Correct System Sizing: When an air conditioner keeps short-cycling, it’s important to conduct a proper load calculation. This helps us determine the correct system size, so you don’t have to deal with an excessively humid home.
• Humidifier Adjustment: Sometimes, the real issue is your home’s humidifier. People sometimes leave the whole-home humidifier on its winter settings. If the humidifier is left on during spring and summer, it can add too much moisture to the air. By adjusting or disabling it seasonally, we can prevent this problem.

Frequently Asked Questions About Sweating Ductwork

To get a better understanding of this issue and what you can do about it, check out some of the questions we often hear from Bandon residents.

Is ductwork sweating dangerous?

While it isn’t healthy over the long run, ductwork sweating doesn’t pose an immediate danger. However, this issue still needs to be dealt with because the moisture can cause mold to grow and attract pests. Over time, it can result in wood rot, drywall damage, and damaged insulation.

Why are my AC vents dripping water in summer?

When the surface temperature of a duct or vent drops below the dew point, water condenses on the cold surface. High indoor humidity, poor duct insulation, a lack of crawlspace insulation, and oversized ACs can all increase the likelihood of this problem occurring.

Can a dehumidifier stop ductwork from sweating?

A dehumidifier helps with ductwork sweating by lowering the humidity level of the air. However, this doesn’t address the root cause, which is often poor duct insulation. To fix the problem, you need to have your ducts inspected and insulated properly.

Does an oversized AC cause ductwork condensation?

An oversized AC installation can contribute to ductwork condensation. Because the AC’s capacity is too high for your home’s needs, it reaches the chosen temperature before it has a chance to reduce your indoor humidity enough. As a result, your indoor air is more humid than it should be, so condensation will occur.

Schedule a Ductwork Inspection With Alpha Heating & Air

Why does ductwork sweat? And what can you do about it? At Alpha Heating & Air, we can answer all of your HVAC questions. Our trusted technicians can ensure your duct insulation, crawlspace moisture, and system sizing are set up to minimize indoor moisture.

Discover our same-day services and upfront pricing by reaching out to us at 541-216-4554.