If a roof leak has soaked the insulation in your attic, fix the roof first, then look at what kind of insulation you have. Blown-in insulation that got wet should come out and be replaced. Fiberglass batts can sometimes be dried and put back, if the water was clean and the batts aren't flattened or moldy.
That's the short version. The rest of this post is how to tell which situation you're in.
Stop the water before you touch the insulation
Drying insulation under a roof that still leaks just sets you up for the next storm. The EPA's guide to mold and moisture is plain that if you clean up mold but don't fix the water problem, the mold is likely to come back. The same goes for wet insulation.
So the order is: find where the water gets in, repair it, then deal with what's under it. If the leak is still active, start with what to do while your roof is leaking. If all you have so far is a brown ring on the ceiling, check whether the stain is really the roof before you pull anything up.
Find out what kind of insulation is up there
If you go up, pick a cooler part of the day, take a flashlight, and keep your feet on the joists. Look at the insulation around the wet spot and away from it.
- Blown-in (loose-fill): a loose, fluffy layer poured over the attic floor, covering the joists. It may be gray and papery (cellulose) or made of loose fibers.
- Batts: blankets or rolls laid in strips between the joists, sometimes with a paper facing.
- Vermiculite: small pebble-like pieces, gray-brown or silver-gold. If that's what you see, stop there.
The EPA tells homeowners to assume vermiculite insulation contains asbestos and not disturb it. Don't remove it yourself, don't store boxes on it, and keep any trips into the attic short. Work that would disturb it is for a professional asbestos contractor.
Why wet blown-in insulation comes out
The North American Insulation Manufacturers Association says all loose-fill insulation of any kind that gets wet should be removed and replaced, because it can lose its insulating value (its R-value) when wet. It adds that cellulose treated with fire retardants can also lose its ability to resist fire after it's been soaked.
So with blown-in insulation, the job is to take out the wet section, let the area underneath dry, and put new insulation back to the right depth.
When fiberglass batts can be dried
Batts have more room for a judgment call. The same manufacturers' association says fiberglass and rock or slag wool batts that get wet from a clean water source, such as a drinking water pipe, can be removed, dried out and reused.
Rain coming through a roof isn't water from a drinking water pipe. It has run over shingles and the roof deck before it reached the attic. Whether that counts as clean is something to ask whoever inspects it, and you should expect them to look at the batts themselves before deciding.
The EPA is stricter. Its water damage table, which comes from its guide for schools and commercial buildings and is written for clean water damage, lists cellulose and fiberglass insulation alike as "discard and replace". So the sources don't fully agree on batts. Replacing them is the cautious choice, and drying them is only worth trying when every sign below is clear.
Signs the insulation is past saving
Whatever type you have, plan on replacing the insulation if you see any of these:
- it's matted down or flattened where the water hit, since insulation a leak has flattened doesn't insulate as well
- there are dark spots of mold on it, or on the wood around it
The EPA says absorbent materials may have to be thrown away if they become moldy, because mold can grow into the spaces and crevices inside them.
The ceiling below gets its own decision. The EPA's table says drywall may be dried in place if there's no obvious swelling and the seams are intact. If not, it gets cut out and replaced. That's worth knowing before you paint.
What you can do today
If you can get into the attic safely:
- Take photos of the wet area, the insulation and the roof deck above it.
- Move anything stored on or near the wet spot so it can't soak up more water.
- If you see mold and decide to handle the insulation yourself, wear what the EPA suggests for mold cleanup: a well-fitted respirator, long gloves and goggles without vent holes.
- Leave it alone and call someone if the ceiling is sagging, the insulation is vermiculite, or you think mold is hiding where you can't see it. For hidden mold, the EPA suggests hiring an experienced professional.
Don't leave soaked insulation lying on the ceiling and hope it dries by itself. Wet insulation can keep moisture pressed against the drywall below it.
How we handle wet insulation after a leak
We start on the roof. Roof repair at Fit Roofing & Construction covers leak detection and flashing repair, so the water stops before anything goes back in the attic.
Then we look at the insulation. Our attic insulation work includes removing insulation that is wet, flattened or damaged and replacing it. We replace the insulation the leak damaged and bring it back to the level your attic needs. While we're up there, we check for air leaks around the hatch, light fixtures and pipes, and we plan the insulation together with your attic ventilation so the vents still move air when the new insulation is in.
Before any work starts, you get a proposal showing the material options, the timeline and the price, and we answer your questions first.
If a leak has soaked your attic, book an attic insulation inspection and find out what can be dried and what needs to come out.