Sometimes. Fiberglass that's only lightly damp at the edges can dry in place once the leak is fixed. Insulation that's soaked, matted down, stained or smells should be removed. Wet insulation holds water against the ceiling, loses most of its insulating value, and can grow mold. Cellulose, which is made of treated paper, holds even more water than fiberglass and rarely recovers.
| Insulation type | When wet | Usually |
|---|---|---|
| Blown-in fiberglass | Lightly damp at the edges | Can dry; fluff and monitor |
| Blown-in fiberglass | Soaked, matted or stained | Remove and replace |
| Blown-in cellulose | Any significant wetting | Remove and replace; it packs down and holds water |
| Fiberglass batts | Damp only on the surface | May dry |
| Fiberglass batts | Soaked through | Remove and replace |
| Any type with rust, sewage or a musty smell | Contaminated | Remove and replace |



