Closeup on the edge of a vapor barrier where it meets a wooden baseboard

Water vapor barriers are integral to many homes, especially in humid climates. They help keep moisture from seeping into walls and ceilings, which can lead to mold and mildew. 

However, one huge concern that baffles many homeowners is whether or not these vapor barriers can cause mold.

In this guide, we’ll go in-depth about vapor barriers, including what they are, how they work, how they can cause mold, and what to look out for to ensure your home is mold-free.

So, let’s get into it!

Do Vapor Barriers Cause Mold? 

Vapor barriers do not cause mold, provided they are installed correctly with no gaps or holes. Moisture will only become trapped if the vapor barrier is installed incorrectly, creating ideal mold growth conditions. Mold requires food, water, oxygen, and warmth to grow and thrive.

If you’re concerned about the potential for mold growth, it’s vital to have your vapor barrier installed by a professional. 

What Is a Vapor Barrier, and How Does It Work?

Mainly installed in crawlspaces, attics, and basements, a vapor barrier is a heavy-duty material typically made of plastic or foil sheet that helps prevent moisture and water vapor from seeping through walls, ceilings, and floors. 

A moisture barrier installed on a basement floor in a home

Normally, air and water vapor can move freely through building materials like drywall, insulation, and flooring. However, when these vapors come into contact with a cold surface, like a window or an exterior wall, they condense and turn into liquid water. If this happens often enough, it can effectuate mold growth.

Vapor barriers work by creating a barrier that water vapor cannot penetrate. This way, when the air inside your home comes into contact with cold surfaces, the water vapor will condense on the vapor barrier instead of the surface. 

This application prevents moisture from diffusing into your walls, ceilings, and floors and helps insulate your home. Damp areas are often cooler than dry areas, so by avoiding vapor entering your home, you can help keep it warm.

How Vapor Barriers Can Cause Mold

While this seems counterintuitive, it is possible for a vapor barrier to actually cause mold. Since these barriers are impermeable to water vapor, they can trap moisture inside your walls if not installed correctly. 

If there are gaps or holes in the vapor barrier, water vapor will seep through and condense on the cold surfaces inside your walls or ceilings. Over time, this can lead to mold and mildew growth.

Additionally, moisture can enter through cracks and crevices if the vapor barrier is not properly sealed at the edges. After the water vapor condenses on the cold surface, it causes dampness, which is the perfect environment for mold to thrive.

It is crucial to have your vapor barrier installed by a professional to avoid these problems. They have the expertise to ensure the barrier is installed correctly without any gaps or holes. Additionally, they will offer tips on properly maintaining it to prevent mold growth.

What To Look Out for if You Suspect Mold Growth

While vapor barriers are an effective way to prevent mold growth, there are a few things you should look out for to ensure your home remains mold-free. 

Mold exposure can lead to health problems such as allergic reactions, eye irritation, and respiratory issues, so it’s essential to take the necessary precautions to prevent its growth.

A few things to look out for include:

1.) Musty Odors

A telltale sign of mold is a putrid smell from your walls, ceilings, or crawl space. Microbial volatile organic compounds (mVOCs) give mold its characteristic musty stench. 

If you notice this kind of smell in your home, it’s vital to investigate further to see if there is mold growth. Otherwise, mold can quickly spread through your home and cause significant damage. Not only will this take a long time to repair, but it can also leave you with extremely high repair fees. 

2.) Visible Mold Growth

A picture of a corner of a room showing black mold growing on white walls and ceiling.

Of course, one of the most obvious signs of mold is visible growth on your walls, ceilings, or floors. Mold can appear as green, black, or white growths and often be fuzzy or slimy. Check for mold in damp or dark areas of your home, as this is where it is most likely to grow. 

If you see any mold growth, it’s crucial to take action immediately to prevent the problem from worsening. Hire a professional to immediately get rid of the mold and find out the source of the problem.

3.) Water Stains or Discoloration on Walls and Ceilings

Mold often appears as minor water stains on your home’s walls and other structural surfaces. These stains are usually dark and may be accompanied by mold growth. Bubbling, peeling, or damaged paint can also indicate mold, as the mold is causing the paint to separate from the wall. 

Water leakage from plumbing fixtures or appliances can also lead to mold growth, so check for any leaks in your home and have them repaired as soon as possible.

4.) Allergy Flare-Ups

Mold spores are a common allergen, so if you or someone in your family starts to experience allergy symptoms such as sneezing, coughing, a runny nose, or watery eyes, it could be due to mold exposure. 

Mold can cause an allergic reaction in many people. So, if you start to experience allergy symptoms and there is no other explanation, you may have a mold problem in your home.

5.) Eyes, Nose, or Throat Irritation

Mold exposure can also irritate the eyes, nose, or throat due to the mVOCs emitted from the mold spores. mVOCs can cause a burning sensation in the eyes, nose, or throat and difficulty breathing. 

A homeowner sitting on her living room couch blows her nose

The discomfort is usually worse in a room with high mold growth. If you experience these symptoms, you must leave the area and get some fresh air. Have an expert inspect your home for mold and take the necessary steps to remove it.

6.) Funky Smell From Your HVAC System

Common in standalone air conditioners, central air conditioners, and furnaces, a funky smell from your HVAC system could signify mold growth. The dampness, darkness, and constant exposure to warmth make the perfect environment for mold to grow. 

When the system is turned on, the mold spores are circulated through the house, causing the musty smell. Be on the lookout for mold growth on or near the vents. 

To rule out the mold as the source of the smell, have a professional inspect and clean your HVAC system. Alternatively, you can invest in a HEPA air filter to remove the tiny mold spores from the air and help improve indoor air quality.

7.) A Stubborn Cough That Won’t Go Away

Prolonged mold exposure can cause several respiratory problems, including pneumonia, recurring bronchitis, and asthma. If you’ve had a chronic cough for a few weeks or months, perhaps mold could be to blame. 

If you experience shortness of breath, chest pain, or difficulty breathing, it’s essential to schedule a doctor’s appointment immediately, as these could be signs of a more serious respiratory problem.

How To Prevent Mold Growth

Besides installing a vapor barrier, it’s crucial to be vigilant in preventing mold growth. Sometimes, the vapor barrier might fail, so taking the necessary precautions is always good. 

Follow these tips to prevent mold growth:

1.)  Promptly Fix Any Leaks

Moisture is the main culprit in mold growth, so fixing any leaks in your home ASAP is essential. 

This includes leaks from:

  • Plumbing fixtures like toilets, sinks, and showers
  • Appliances like washing machines and dishwashers
  • Windows and doors
  • The roof
A plumber sits on a bathroom floor as he repairs a leaky faucet

You can fix some of these leaks if you have handy skills. However, hiring a professional for more complex repairs is always best.

2.) Control Humidity Levels

Keep your home’s humidity levels below 60% to prevent mold growth. You can do this by using a dehumidifier, properly ventilating your home, using your exhaust fans when cooking or showering, and not allowing water to accumulate inside your home. When using a dehumidifier, make sure to empty the water reservoir regularly.

A homeowner emptying the tray of a dehumidifier

3.) Check the Seals Around Your Windows and Doors

If the seals around your windows and doors are damaged, water can seep in and lead to mold growth. Inspect the seals around your doors and windows habitually and repair any damage immediately. You can also install weather stripping and door sweeps to help prevent water from entering your home.

4.) Regularly Clean and Maintain Your HVAC System

Your HVAC system is responsible for circulating air throughout your home, so keeping it clean and well-maintained is essential. 

This upkeep includes regularly changing the air filter every 2–3 months during the cooling months and having a professional inspect and clean the system at least once a year.

A profession using a brush for air duct cleaning

5.) Divert Stagnant Water Away From Your Home

Stagnant water is a breeding ground for mold. 

To prevent mold growth, divert any standing water away from your home, including water from:

  • Downspouts
  • Gutters
  • French drains
  • Sump pumps

This water can also find its way to your basement or crawl space if your home is not sloped correctly. If you have a basement or crawl space, regularly check for water accumulation and take measures to dry the area immediately if water is present.

6.) Monitor Your Home for Mold

You can’t prevent mold growth if you don’t know where it’s growing. Therefore, it’s essential to check your home for mold periodically. Inspection is especially crucial if you live in an area with high humidity levels or if you’ve had recent flooding.

Be on the lookout for:

  • Discoloration on walls, ceilings, or floors
  • A musty smell
  • Peeling paint
  • Water stains

If you notice any of these developments, it’s time to do a more thorough inspection. Use a flashlight to check dark and hard-to-reach areas, like crawl spaces, attics, and basements. If you see mold or suspect mold growth, immediately contact a mold remediation specialist.

A homeowner laying on his side inspects his crawl space with a flashlight

Final Thoughts

When properly installed and maintained, vapor barriers effectively keep off moisture and prevent mold growth. However, if not installed correctly or if they fail, vapor barriers can actually cause mold. 

If you suspect mold growth, it’s crucial to take action immediately to prevent the problem from worse

ning. You can also be proactive and vigilant in preventing mold by regularly checking for leaks, fixing any damage promptly, and monitoring your home for mold growth. 

In addition, you can invest in a dehumidifier to help control moisture levels and ensure your HVAC system is clean and well-maintained.

Best of luck!


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