How Do You Dry Wet Insulation in Walls?

The first step is to know what kind of insulation is inside your wall. Fiberglass batts can sometimes dry out if they are only damp and the wall cavity is opened to air. Loose-fill cellulose, spray foam, or mineral wool behave differently, and water can ruin their thermal performance.

If the insulation is wet enough to sag, hold water, or smell musty, drying may not be enough. In that case, the wet material usually needs to be removed and replaced. A water damage pro can help you identify the type and decide whether drying is worth trying.

• Fiberglass: may dry if opened and ventilated
• Cellulose: often clumps and loses R-value when wet
• Spray foam: can trap moisture against framing
• Mineral wool: more water-resistant but still needs drying
• Always check for mold growth before re-closing walls

Dehumidifiers help remove moisture from the air, which speeds up drying in the wall cavity. Place a dehumidifier near the open wall and keep the room sealed off from the rest of the house for efficiency. A temperature of around 70 to 80 degrees Fahrenheit helps air hold more moisture, so use a space heater if the room is cool.

Do not use high heat, as it can warp wood framing or damage the drywall. Run the dehumidifier for several days, checking the insulation's moisture level with your hand or a moisture meter. If you have a moisture meter, readings above 20 percent indicate the material is still wet.

For large areas, a water damage pro might use industrial dehumidifiers and air movers. That kind of setup can dry deeper into the wall structure, but it is not a quick fix.

• Set dehumidifier to 50 percent relative humidity
• Keep room closed to concentrate drying
• Use a fan to circulate air through the wall opening
• Check moisture with a meter if available
• Avoid heat above 80 degrees to prevent damage
• Run drying for at least 48 hours before reassessing

Drying wall insulation is not always straightforward, especially if the water came from a hidden leak or sewage backup. A water damage pro can use moisture mapping to find all wet spots and structural drying equipment to dry the framing. They can also tell you whether the insulation is salvageable or needs replacement.

Humid summers can slow natural drying, so a pro can set up equipment to manage that humidity and prevent mold from spreading. The cost depends on the size of the affected area, the type of insulation, and how long it has been wet.

Policies vary, and your insurer decides what is covered. Check your policy to see if insulation drying or replacement is included after a covered water loss.