Is it cellulose insulation falling through small holes in the fan housing? Is there an attic above?

I think the attic extends above it; if not, very close. Some electric work in the adjacent room was done through the attic. I don't know what cellulose insulation looks like. Is that what it looks like to you? If so, what is the remedy?

It does look like sawdust to me, but that would have stopped happening eventually. A fan housing in an attic should be spray foamed all around it to make it air tight and to stop loose fill insulation from going through the various holes in the housing. It would be good to make sure this fan vents to the outside too but I dont think insulation would make its way through the vent pipe, its probably coming from the small holes in the housing.

The strangest thing to me is that it happens without anyone being near that part of the house.

I did not suggest insulation was coming thru the vent pipe.I suggested the fan may not have been vented and sealed properly allowing insulation to enter the fan.

It would not surprise me in the least if the fan was not vented and sealed properly. In fact, the surprises are anything in this remodel that was done properly.

Given that our contractor is not responding to our messages regarding this problem, who would we contact to fix it (assuming he will not), and how much might this cost? Is it something we can do ourselves? I don't know if we can access the area we need to reach from below. Would someone have to crawl into the attic? Some work (not sure what) was done by cutting a hole in the ceiling in the next room, since the regular attic access isn't very close.

It will have to be checked from the attic.There should be a pipe or flex hose from the top of the fan going to a vent outside the house.It should be insulated and air sealed.

A handyman can crawl up there and check it, install roof vent cap and 4" vent if not vented properly, then spray the housing with fireblock.

The attic would have to be smaller than 30 s.f. and less than 30" in height to not be required to have an access hatch but the renovation might not have triggered that requirement although, if appropriate, it should have been added since it is for fire fighting

Unless the fan housing has been tested and rated for being covered with insulation it should be enclosed in an insulated box.

Could this be pollen and air is moving in the wrong direction?

I've never seen the attic myself, but I'm sure it exceeds those dimensions. There is access through a closet in another room, I'd guess 20 ft. from the bathroom fan. I don't think it's pollen, and the debris falls when the fan isn't on; the fan has hardly been on at all. There was previously a light/fan combo in the bathroom, but I don't think it was in the exact same location. Or, if it was, perhaps it also was installed improperly, but we never had the debris problem before.

My contractor finally responded, saying that it's insulation and "I can examine the fan to see why insulation is coming in, and how to stop it from doing so." He has done a lot of things improperly and has been deceptive, so I want to be prepared to tell him what has to be done as specifically as possible. From the replies above, it seems that he not only has to stop the debris from falling, but also has to meet certain code criteria. Is that correct? I'm in Maryland, if that helps.

The relevant code requirement is that the exhaust terminate at the exterior of the house not inside the attic. It would be nice if the duct was metal with the joints secured with screws rather than a flexible plastic one but that is probably too much to hope for.

IMO the most likely cause of the debris is a disconnected or torn flex duct. I can't believe those things are still allowed in houses.

could be sheetrock dust and/or insulation coming
from oversized cut in the sheetrock ceiling.
take the cover back off & take some pics.

you say: "We removed the fan cover, but all we see is a cylinder covered in this stuff. It seems too fine to be sawdust,"

I have no idea what this could be...spray foam in the gap?
backing of some sort?

are you removing the cover by taking out the lightbulb, unscrewing the acorn nut & taking out light fixture/reflector by unplugging the light
from inside the housing of the fan?

this will expose the opening around the housing in
the sheetrock.

take that picture & post it.

personally, I'd start in the easiest spot to investigate &
save any attic investigation for early morning.

best of luck.

I've already said that and sent photos. I have no plan to explore the attic myself; my husband just removed the outer cover and looked up, hoping he'd see a minor issue he could fix himself. Since that wasn't the case, it is the contractor's responsibility to fix it, either himself or by paying for someone else to do it. I just want to make sure I understand what needs to be fixed so that he does it properly, and so that he knows I know what "properly" means. It sounds like shortcuts were taken when the fixture was installed.

If you don't get on a ladder yourself and explore what the issue might be, then you'll never actually know the appropriate fix for the problem, or if the actual problem gets fixed by whomever. You're overly concerned about the symptom that isn't the issue. Find out the issue. Explore the attic and look at the duct from the attic and with the housing removed from below.

Post pictures with the vent fan removed.

why remove the vent fan?
just share the pics taken with the cover
off. that would tell us more than pics
of debris on toilet.

oh well...

Hi i'm having the same problem. Did you fix yours and what was it?

same problem with our bathroom.. we just moved in and wondering what was that falling from the fan in the bathroom.. i vaccumed everyday the vent and floor.. should we contact out agent or the preveuws owner?

I am having the same problem...anyone ever find out the problem? Prior responses say that it is insulation...but I am smart enough to know that insulation is not like powder. And yes, my unit exhausts to the outside, not in my attic.

I have this same problem!!! I live in a mobile home and just bought this place.

Anyone from this chat get a definite answer on what this was and a solution? Thanks!

@feddup What was the resolution on this? Thanks!

@robert wood did you ever figure out what was causing this? Thanks!

Yassin Ata did you ever find out what was causing this? Thanks!

That looks like “frass” from carpenter ants. They’ve been establishing a nest in your ceiling, chewing into the insulation to do it. Whatever material they find up there, the frass will resemble that. You can try tapping the ceiling to find a void and spraying some foam into it. Then spread a lot of ant bait around so they don’t survive as they move to a new spot.