A man working on insulation in the wall, with a water symbol and question marks to the right of him.

Insulation, when installed properly, is a fantastic luxury that keeps us warm in the winter and cool in the summer. However, if that insulation gets wet, it could be a different story. Is wet insulation a risk and if so, what can be done about it?

Wet insulation can become a health risk. If insulation is left wet for long enough, mold and bacteria will start to grow in it. This severely decreases air quality and can lead to major health risks. The longer wet insulation is left alone, the more bacteria grows and the greater the risk to your health and home becomes.

There are many different kinds of insulation, and each brings its own pros, cons, and risks. Read on to learn more about each of them, as well as what to do when dealing with wet insulation!

Wet Insulation: The Risks

Wet insulation is usually found in the roof where leaks and water exposure is more likely and possible to occur. Replacing insulation can be an expensive, time-consuming, and labor-intensive process, but it is also an issue that cannot be ignored. The moment you suspect your insulation is wet, you should check it out. Here’s why:

Higher Energy Bills

Believe it or not, wet insulation might actually cause your energy bills to go up. Insulation is supposed to repel electricity, not conduct it, but that’s exactly what will happen if the insulation gets wet. Wet insulation also becomes less efficient at its job, so it will take twice as much heat in the winter and twice as much air conditioning in the summer to keep your home at a comfortable temperature. If your electrical bills have suddenly gone through the roof, you may want to check your insulation.

Air Quality

One of the more commonly known issues with wet insulation is that it is an air quality reducer. If mold and bacteria start to grow on your insulation, spores and particles that are detrimental to your health will start escaping into the air. If you have wet, moldy insulation, you may start to experience things like eye irritation, respiratory irritation, pulmonary effects, and possibly even things as severe as pneumonia—yet another reason why you should not leave the problem unattended.

Off-Gassing Chemicals

Insulation made with minerals, fiberglass, or wool often contains a chemical called formaldehyde, which becomes another liability if the insulation gets wet. When formaldehyde is wet or starts to experience a lot of humidity, it starts off-gassing. This is not only extremely detrimental to your health, but it will also start to corrode your roof structures from the inside out, including rusting studs and bolts. The levels of gas will decrease in time, but it won’t ever go away on its own unless fixed.

On a similar topic, we covered a lot more on whether or not insulation can cause you to get sick as well. Check out this article to read more on that.

Odors and Smells

If you have wet insulation inside your wall cavity, you might start to notice it giving off an odor. You might not necessarily know where it’s coming from, but you will definitely notice it there. If the wetness is left unattended for long enough, you might even start to see dark mold spots growing on your wall, or ceiling, or both. If possible, you should try to get it checked out by a professional once you start noting a mildewy smell. You will definitely know something is wrong the moment mold starts growing on the wall.

Roof Leaks Lead to All Kinds of Issues

Water that has accessed your insulation will likely have accessed beams and rafters, causing mold and rot on your wood. That, too, will compromise your safety. If the rotting spreads, you may end up having to replace more than just the insulation, so get on it as soon as possible!

A picture of the ceiling of a home with ripples in the plaster, indicating water damage and roof leaks from above.
If water is getting to the underside of your ceiling, there’s a good chance it’s gone through the insulation on the floor of your attic, or in the insulation in your roof structure.

Causes/Fixes of Wet Insulation

Now you know why wet insulation is bad, so next, you need to learn how to fix it. Here are a few common culprits that might be getting your insulation wet:

Air Gaps and Condensation

One of the most common causes of wet insulation in a wall cavity is air gaps and condensation. When cold air gets trapped inside a wall, the warm air will cause it to condensate, thus getting the insulation wet. Cold air usually gets in through siding or window and door framing/casing. If there are too many air gaps, this problem will grow steadily worse, so definitely check for those if your mission is to minimize condensation, and if you find any, make sure to seal up those gaps.

Overhead Drips

Overhead drips are also a common problem, and these can affect wall insulation as well as attic insulation. If your attic is not properly vented, moisture and condensation will form and drip onto the insulation (lack of air circulation). This can seep all the way down through the walls, sometimes soaking the drywall (you will be able to tell if this happens). Fortunately, overhead drips are also a tad easier to identify because they leave telltale signs (like puddles forming on the floor of your attic). You should take immediate action if you notice this occurring. Try to install proper ventilation to promote better air circulation.

Leaky Pipes

Another issue you will likely encounter is a leaky pipe. Most copper plumbing pipes are pretty secure, but every once in a while one of them is bound to develop pinhole leaks that will spray enough water to cause a problem. Uninsulated copper pipes that carry cold water are hotspots for condensation, which often drips either down the walls or onto the floor. Again, however, this is usually a pretty diagnosable cause, so just keep a sharp eye out for this. You can patch any holes you find, but it is probably a better idea to replace any leaky pipes.

A picture of the bathroom plumbing pipes leaking water from the bottom.
If you have leaky pipes, especially on high floors of the house, it can start finding insulation in the walls.

You may also be facing a problem with your upstairs plumbing. If your toilet, sink, or shower is having issues and leaking, this could very well be contributing to the conundrum with your insulation. If you are starting to notice drips from a leaky toilet or poorly sealed shower drain, get it fixed as soon as possible. This is definitely not something you should let slide because it can lead to a whole slew of problems. Wet insulation is just the beginning!

Insulation Types: Pros and Cons for Each

Now that we’ve talked about risks and causes, let’s talk about different types of insulation. Each one has its own strengths and weaknesses and pros and cons to consider. So, without further ado, here’s some info about the three most common types of insulation:

Spray foam insulation is applied in a home
Spray foam insulation going on the surface of an attic floor.


One of the biggest pros to using fiberglass insulation is its easy installation. Fiberglass insulation most commonly comes in rolls or batts and is incredibly easy to set up within the joists of your wall. Additionally, fiberglass is fairly moisture resistant, making it a great choice for homeowners who live in higher humidity regions. In comparison to several other types of insulation, fiberglass has been tested to be fairly sturdy against moisture.

To top it all off, fiberglass is incombustible! That’s right, fiberglass insulation is fire and heat-resistant. This also makes it an incredibly safe choice for insulation in your home. Having an incombustible material snugly fit next to the wooden supports of your home is great protection against fire hazards. Also, fiberglass is renewable, making it an environmentally-friendly choice. Nearly half of fiberglass’ materials are recycled, and the other portions are made from sand, which is completely renewable.

A picture of pink fiberglass in the wall, with a man installing it on the right side.

On the downside, fiberglass insulation is incredibly easy to install incorrectly. If it has been installed incorrectly, it will not be nearly as efficient as other types might be. It might be easy to install, but don’t let that fool you. You still need to take the time to do it right. Additionally, fiberglass insulation does not rate as high as other types as far as resistance is concerned (meaning it is less efficient and less durable).

Cleaning Up: when fiberglass insulation gets wet, it won’t just immediately soak up the water. Fiberglass doesn’t absorb water, so no instant damage will be done to your home’s structure. However, if the problem goes unfixed, that will do damage and seriously decrease the insulation’s functionality. To dry fiberglass insulation out, use a dehumidifier and some fans. If needed, you can even remove the bats from the wall and put them in the sun to dry.

Once you have dried the insulation out properly, put it back and check up on it over the next several weeks. If all is well, you won’t need to replace it at all. However, if you start to notice a musty or mildewy smell around the house, that means the insulation was undoubtedly contaminated and will need to be fully replaced.


Cellulose is loose-fill insulation made from recycled paper and cardboard (newspaper primarily). It can be installed either dry or wet. Many people consider cellulose to be the most environmentally friendly type of insulation since its creation is mostly brought on by recycling. This is one of the most prominent perks of using cellulose to insulate your home. It also tends to be much cheaper than fiberglass insulation.

Additionally, cellulose is treated with boric acid before it is installed. This means it is fire-resistant, mold-resistant, and unpalatable to insects. In some cases, it is also treated with an acrylic binder, making it far less likely to experience a decrease in R-value (which simply refers to an insulating material’s capacity to resist heat flow). Cellulose has been shown to present fewer concerns and risks to the homeowner’s health if it gets wet.

Unfortunately, because cellulose is made primarily of paper, this makes it far more susceptible to moisture absorption than fiberglass or foam. Additionally, while it has been proven to be cheaper than fiberglass and foam, the installation costs can be pretty high. Plus, when installed, it creates a significant amount of dust. If you are installing cellulose, you can’t afford to not have a breathing mask. Dust inhalation can be severely detrimental to your health.

A picture of grey loose-fill cellulose insulation in a big yellow bag with a scoop in it. Having paper properties however, means getting it wet will cause issues.
Loose-fill cellulose insulation can be very economical and energy efficient. Due to being made of some paper materials, this makes it susceptible to absorbing moisture.

Cleaning Up: While it is possible to remove and dry out cellulose bats, likely, it won’t work. If you are lucky enough, you may be able to remove the batting and lay it out in the sun or under a fan to dry. However, as mentioned above, cellulose is a high paper-content material, making it extremely easy to get damp and grow mold. If the leak you are experiencing is significant enough, chances are you will have to totally replace everything. It might sound like a pain, but it’s a small price to pay when dealing with potential health hazards.

Spray Foam

Foam insulation is growing rapidly in popularity. One of the biggest reasons to invest in spray foam insulation is its incredible capability to seal cracks and gaps. It provides an air-tight seal and can add some pretty strong support to the support system of your home. Quite possibly one of the best things about foam insulation is its water resistance. Because it expands and hardens, it doesn’t allow water to permeate the surface. This makes it a fairly ideal insulation choice.

Foam insulation also deters mold and mildew buildup and often has a much longer lifespan than either fiberglass or cellulose. Unlike fiberglass and cellulose, spray foam insulation will not lose its R-value over time. It can if it has been installed improperly, but as long as the installer knows what they’re doing, it shouldn’t be that big of an issue.

A man in full protective gear is sitting on the attic floor while he sprays spray foam insulation on the underside of the attic ceiling.
Perhaps the most water-resistant type of insulation, spray foam is also excellent for energy efficiency.

One of the biggest cons that come with using spray foam insulation is the possibility it has of shrinking. While it is pretty sturdy for the most part, any shrinking that occurs will greatly lessen its insulative capabilities. This is most likely to happen in areas where extreme temperatures and temperature changes happen frequently. Additionally, if you want to install your own foam insulation, significant experience is required to get it right. Don’t attempt it unless you know what you’re doing!

You can check out some more warnings about spray foam here as well if you want to dig in further.

Cleaning Up: Luckily, as said before, foam insulation repels water and provides a moisture barrier. This means that water cannot usually penetrate the surface and it will usually evaporate after a little while. If you do discover water on your foam insulation, all you have to do is mop it up or wipe it off. The only time you will have a problem is if water has somehow gotten between the insulation and the wall—it might be causing the wood to rot. Even if this does not appear to have happened, you will probably want to check just in case.

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