Is Fiberglass Insulation Mold Resistant?

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When you're looking for the best insulation, you're likely to hear experts suggest fiberglass. But even with all its benefits, there's one question most people tend to ask: is it mold-resistant? If you're a homeowner who worries about this concern, we're glad to let you know we've got the answers you need in this post!

The materials in fiberglass are inorganic and resist mold, so it's an excellent solution for insulating and moisture issues. However, mold can grow behind fiberglass insulation and turn it into a food source. So, most would recommend getting fiberglass insulation without backing to prevent mold growth.

Although fiberglass doesn't feed mold, there are situations where bacteria spreads within it, even without passing through the insulation. Keep reading as we explain why and when this happens and what you should do to remove it.

Fiberglass insulation installed on a basement roofing, Is Fiberglass Insulation Mold Resistant?

Can Mold Grow On Fiberglass Insulation?

Yes, mold can grow on fiberglass insulation, particularly if it has paper backing. The primary materials used by fiberglass are inorganic. Therefore, it cannot support mold growth, so it becomes resistant.

Instead, mold will grow on the paper backing of fiberglass insulation, especially under the right conditions. While fiberglass tests prove the material to be a good counter for mold, it may still attach itself to the insulation with enough moisture and the right temperature.

If you own cellulose, read this post to know how it works with mold: Is Cellulose Insulation Mold-Resistant?

One way to go around this is by purchasing fiberglass insulation rolls that don't come with a backing. Fiberglass also comes with foil backing, which mold is less likely to stick on.

Check out the Frost King Foil Backed Fiberglass Wrap on Amazon.

Does Fiberglass Insulation Need A Vapor Barrier?

vapor barrier is necessary when installing fiberglass insulation in most locations. Adding it helps prevent moisture from reaching spaces that water vapor may harm, damage, or grow bacteria.

A close up vapor barrier in installing roofing and fiberglass insulation on the bottom

Fiberglass insulation bought without a backing may still effectively insulate, but it won't be able to hold off mold as much as fiberglass with a paper or foil backing. Vapor barriers serve as an alternative for these circumstances.

Keep in mind that a vapor barrier won't always be mold-resistant. But because of its moisture-reducing properties, a vapor barrier can hinder the spread of mold and mildew.

Click here to see the Blue Summit Vapor Barrier Tape on Amazon.

Signs Of Mold In Fiberglass Insulation

Even if fiberglass insulation can resist mold, look out for any symptoms that indicate your fiberglass insulation may be growing bacteria. These include the following signs:

  1. Insulated walls or spaces give off a strong musty smell.
  2. You experience allergy symptoms and colds more frequently in the suspected room.
  3. There are patches of discoloration on your insulation, either in black, gray, green, or brown.

Once any of these seem evident, check the status of your insulation to avoid further problems.

What Type Of Mold Can Grow On Insulation?

Fiberglass insulation in a crawlspace

Next to the signs, it helps to identify the different molds you may find to understand how to counter them. Here are the types of mold that could grow on your insulation:

White Mold

It's the hardest to identify because of its color, especially when it's directly on fiberglass. Observe your insulation for any unusually fuzzy or powdery textures and unpleasant odor.

Because it's challenging to detect, it can become a big problem for your health and your home's structure.

Black Mold

Black mold is one of the quickest types of mold to identify since it comes in the colors black or dark green. Most refer to this as the most toxic mold, but it's just as harmful as other variants.

Green Mold

Like black mold, green mold also comes in a distinct and easily identifiable color. It is more common on food like bread and fruits, but it tends to grow on damp surfaces or poorly ventilated locations.

How To Get Rid Of Mold-Infested Insulation

One way or another, you're bound to encounter mold around your home, including in your insulation. For complicated issues, it's best to have a professional assist you to ensure safety.

But with smaller jobs, you can remove them yourself with the following steps:

1. Put On Your Protective Gear

Safety is essential when coming in close contact with mold. As much as possible, make sure you have your whole body covered or use disposable clothing with safety goggles and gloves.

Experts recommend using a half-face respirator since dust masks may still allow mold spores to pass through the edges of the cover.

Click here to check the Kischers Half Facepiece And Safety Goggles Set on Amazon.

2. Cover The Floor In Cloth

Cover the floor with a cloth and tape the edges to the wall. It will keep the mold spores from falling off or escaping once it's time to gather the cloth.

Take note, you will dispose of the cloth afterward. So, use any piece you want to trash or plastic options.

3. Take Out The Drywall

Cutting a square hole for installing a switch rough in

Start cutting the drywall around the mold-infested insulation in small sections, placing each cut section into a contractor trash bag. Even when you don't see the mold on your drywall, it feeds off this material, so disposing of and replacing it is ideal.

Get the Tough Bag Large Industrial Black Trash Bags on Amazon.

4. Roll Up The Insulation

Technician unrolling a huge roll of fiberglass insulation

Take the bottom edge of the insulation and slowly roll it upward. If it gets stuck on wood, gently tug or carefully free it from the studs.

It's crucial to work with extra care when rolling the insulation to prevent the mold spores from spreading outside. Place each roll into a trash bag and seal it immediately.

Repeat these steps until you take off all the moldy insulation.

5. Secure The Cloth

After bagging and sealing all the moldy insulation, carefully remove the tape from the cloth and fold it inward. Start from the outer edges, then fold the new edges the same way. Doing this will keep any mold spores inside the cloth.

Keep folding the cloth until it's small enough to fit in a contractor bag. Seal it and take it outside with the rest of the bags.

6. Disinfect Your Gear And Space

Take off your protective equipment and immediately launder anything that needs washing in hot water and color-safe bleach. If you are throwing out disposable items, be sure to seal the bags.

Cleanse and disinfect the materials and tools you used with a mixture of 1 cup bleach and a gallon of warm water. Wipe down contaminated and surrounding surfaces as well.

Be sure to shower after cleaning up to eliminate mold spores on your skin.

Does Insulation Prevent Mold Growth?

Mold accumulating and spreading on the wall

Generally, insulation can prevent mold growth because of lowered humidity and condensation levels. The reason is that most of them can hinder the transfer and spread of water vapor to different spaces around a home.

Some insulating materials have mold-resisting properties, like fiberglass, that add to the ability of the insulation to hinder condensation and moisture collection.

Is It OK For Fiberglass Insulation To Get Wet?

Although fiberglass insulation properties may be compromised when wet, it can usually retain these properties after properly drying out without getting compacted.

There are cases where the water goes in-between spaces in the walls and reaches your insulation, causing the insulation to be wet or moist. So, you must check for any gaps or leaks in your foundation.

If you find any cracks or holes, seal them as soon as possible before water infiltration. That way, you can maintain the efficiency of its thermal and insulating properties.

However, remember that dirt and moisture can deposit in your insulation, which may later cause bacteria growth. So, it's best to dry out the insulation at the soonest time.

Read this post to know how long fiberglass insulation can stand: How Long Does Fiberglass Insulation Last?

The Verdict

Fiberglass insulation installed on a basement roofing

Fiberglass insulation is naturally inorganic, making it a mold-resistant material. Despite this, there may be instances where it comes in contact with mold, typically when its backing grows the bacteria.

Identifying if you have mold-infested insulation as soon as you notice one of the signs will lower the chances of its spread and reduces any potential health complications and structural damages. You can also add vapor barriers or choose different fiberglass insulation options to further prevent water vapor from getting through.

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