What Happens If My Insulation Gets Wet?

Insulation is designed to trap air pockets and create a barrier against heat transfer. When insulation gets wet, water replaces the air inside those pockets, drastically reducing its effectiveness. Whether from roof leaks, plumbing issues, or flooding, wet insulation can lead to bigger problems than just a loss of energy efficiency.

Fiberglass and Moisture

Fiberglass insulation does not absorb water but instead allows it to pool between the fibers. While it may dry out in some cases, once fiberglass is wet it tends to clump and lose its structure. This reduces its ability to insulate properly. In addition, damp fiberglass can harbor mold and mildew, which spreads quickly inside wall cavities.

Spray Foam and Moisture

Spray foam insulation is more resistant to water than most other types. Closed-cell spray foam in particular repels moisture and can even act as a vapor barrier. However, if water finds its way behind the foam, it can still damage wall materials and framing. For this reason, it’s critical to address the source of the water intrusion immediately.

Cellulose and Moisture

Cellulose insulation is highly vulnerable to water damage. Made from recycled paper, it can absorb and hold large amounts of moisture. Wet cellulose compresses and loses its insulating ability almost instantly. It also becomes a prime breeding ground for mold. In nearly all cases, wet cellulose needs to be replaced.

Mineral Wool and Moisture

Mineral wool is naturally resistant to moisture and dries faster than fiberglass or cellulose. It does not promote mold growth and generally maintains its insulating properties better than other options when exposed to water. That said, prolonged saturation can still cause performance issues.

Health and Structural Risks

Beyond energy efficiency, wet insulation creates health hazards. Mold and mildew can lead to respiratory issues, allergies, and unpleasant odors. Water-damaged insulation can also cause wood framing to rot, weakening the structural integrity of your home. Ignoring the problem only makes it worse over time.

What to Do if Your Insulation Gets Wet

If you suspect wet insulation, the first step is to identify and stop the source of the water. Next, inspect the damaged areas to determine whether the insulation can be dried or must be replaced. In most cases, removal and replacement are the safest solutions, especially with cellulose or heavily saturated fiberglass. Working with a professional insulation contractor ensures the problem is handled correctly and prevents long-term damage.

Conclusion

Wet insulation is more than an inconvenience—it compromises your home’s comfort, safety, and efficiency. Acting quickly to repair the damage and replace affected insulation protects your investment and ensures a healthy indoor environment.