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What to Do When Your Insulation Gets Wet

Conditions are often rainy and humid in Chicago. While moisture has benefits, such as helping plants grow, high humidity does have side effects: The water can get inside your home and damage your insulation. Has this happened to you? Here’s what to do when your insulation gets wet.

What to Do About Different Types of Wet Insulation

Various types of insulation respond to moisture differently. Some aren’t damaged at all, while others must be dried out to prevent mold growth. Use the information here to act quickly once you realize your insulation is wet.

Wet Spray Foam Insulation

You know your home has spray foam insulation if wall and floor cavities are filled with hard white foam. Though spray foam doubles as a moisture barrier and creates an air-tight seal, the leak is still problematic because water can damage the wood surrounding the insulation. Find the hole and seal it to protect your home’s porous structures from moisture damage.

Wet Fiberglass Insulation

Do you see pink batts or loose-fill insulation in wall and floor cavities? If so, your home is insulated with fiberglass. This material is made of tiny strands of glass, so it doesn’t absorb water. However, when moisture fills the air pockets between the fibers, the insulation loses its ability to slow the transfer of heat. After all, water is a conductor, so wet fiberglass insulation is about as effective as no insulation at all.

To help fiberglass insulation dry out, place a dehumidifier or fan in the area. If possible, remove the affected batts and transfer them to a warm place to dry. Once dry, return the insulation to the wall or floor cavity where it came from. Inspect the fiberglass again in the next few weeks, and if it starts to smell funny, this means it was contaminated with dirty water. You should replace it to avoid affecting your indoor air quality.

As always, we do not recommend doing these tasks on your own. Call on your trusted insulation experts at ThermaSeal/Lakeside Insulation to get the job done properly and safely.

Wet Cellulose Insulation

You have cellulose insulation if you see loose, gray fibers in wall and floor cavities. Cellulose is made primarily of recycled newspaper, making it a plant-based product that can be difficult to restore after getting wet.

If the portion of wet cellulose insulation is small enough, you might be able to remove it, let it dry for a few days and then put it back. However, if the leak was more extensive, a more substantial portion of insulation may have gotten wet. Mold can begin growing within just a few days, so total removal and replacement may be necessary.

Keep Your Insulation Dry

After drying out or replacing your insulation, you probably feel relieved to have the incident over with. To ensure you never experience wet insulation again, follow these tips:

FAQs About Wet Insulation

Can insulation be “waterproofed”?

Yes; and basement insulation, especially, should be waterproofed.

Crawl spaces can also benefit from waterproofing. There’s a difference between “encapsulating” and “insulating” an area like a crawl space; what you need depends on plumbing, flooring and other variables. Whether you have a new build or renovation project, contact us about waterproofing services for your property.

Can mold dry out and die?

No. If a moisture source ends, mold can lie dormant for a while, but as soon as moisture is reintroduced, it begins to grow and spread. Mold is dangerous in any form; it must be eliminated and prevented.

How can insulation get wet?

Roof leaks are one of the leading causes of wet insulation. A roof leak can be quiet but deadly and do a great deal of damage before you discover it. Other wet insulation causes include:

  • Air seepage (windows, doors, siding gaps, exterior cracks)
  • Ground moisture (basement/crawl space insulation)
  • Plumbing leaks
  • Snow (it can literally blow into your insulation from an outside vent)

If you realize your home is at risk of wet insulation, talk to a professional about how to prevent a disaster. Live in a new build? If your home was built right, there shouldn’t be an issue. Conscientious contractors use insulation pros to ensure safe, dry insulation for new-home builds.

How do you dry out a damp attic? Does wet insulation have to be replaced?

If you have an attic problem and your insulation gets wet, put a fan on it to begin drying it out. If, after two days of nonstop fanning and drying attempts, there is still dampness on, in, or around the insulation, you’ve done all the DIY you can do. At that point, it’s time to contact your local insulation professionals. If there’s a safe way to salvage your insulation and save money, we’ll find it.

How long does it take for mold to grow on wet insulation?

Mold begins growing between 24-48 hours after your insulation gets wet.

How much will repair or replacement of wet insulation cost?

It’s not the most popular answer, but the truth is it depends. Variables include the amount of moisture, the length of time your insulation has been deteriorating from moisture, and the type of insulation you have.

Another unpopular answer is, “It doesn’t matter.” Whether it’s a $200 fix or a $5,000 repair, you have to address the problem of wet insulation. And you need to resolve it quickly before structural damages lead to even more expensive repairs.

Other things to know about wet insulation:

  • Closed-cell foam insulation provides a better defense to water and makes for better insulation near exterior walls and roofs.
  • Open-cell foam insulation is great for indoor use but acts like a sponge when exposed to exterior moisture.
  • Wood fiber insulation soaks up water like a sponge and compromises surrounding structures (like your roofing).

Is wet insulation dangerous?

Absolutely. Aside from the potential to cause expensive damage to your property, wet insulation poses serious health risks because it encourages mold growth, which reduces your indoor air quality. Good IAQ is critical for people suffering from asthma or the elderly.

What’s the best insulation?

Like any investment, insulation increases the value of your property. Insulation products have distinct advantages and disadvantages, so the “best” insulation for your property can include more than one type:

  • Cellulose – Made of 80% recycled materials, so the popular choice for environmental consciousness.
  • Fiberglass – Easy, energy-efficient, and popular. Fiberglass provides a good sound barrier and promotes healthier IAQ.
  • Radiant barrier – The best choice for soundproofing.
  • Spray foam – Creates a very tight seal.

Call on the Insulation Experts in Chicago

When your insulation gets wet, you need to act fast! Let ThermaSeal/Lakeside Insulation help you salvage as much insulation as possible. We’ll reinstall the amount we can and replace any moldy portions with new insulation to keep your home comfortable, clean and energy-efficient in all seasons.

Infographic explaining what to do if your insulation gets wet

Infographic explaining what to do if your insulation gets wet

If you live in the Chicago metro area, please contact us to learn more or to schedule the insulation services you need!

Products We Install

Our team installs both batt and blown-in fiberglass insulation.


Help prevent mold and excessive moisture infiltration in homes you build with our waterproofing services.


At Thermaseal / Lakeside Insulation, we understand the role a floor plays within a building system by controlling sound and fire.

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