I believe I have an issue with blown in cellulose insulation infiltrating into the house from the attic.  We have very high level of dust that is noticeable again within several days after dusting.  When you brush it into a pile it has the same consistency and color as fine cellulose. I also noticed in the attic that there is very little insulation remaining around the can lights that are installed in the ceiling. Is it likely that the source of the dust is cellulose insulation infiltration via the can lights?  What is the best way to seal/prevent insulation from leaking through the can lights?  Can I pull the cellulose away and insulate around the lights with foam?  will that cause them to overheat or will the foam migrate into the light? I also have blown in cellulose in the walls but it seems less likely to me that this could much of a contributor to the problem.

Yes, blown in cellulose can infiltrate through canned ceiling lights if the lights were not properly sealed around the drywall area. If your attic has ridge and gable vents, you are getting air flow through there and can create blowing cellulose particles to infiltrate into the home via the canned lights.

As I said before, canned lighting is of the devil.


Cellulose dust is probably something you don't want to be breathing in on a constant basis. The borates and other chemicals they put in it is probably not a good idea to be getting into your lungs and bloodstream.

Seal up the lights and your problem should be solved.

Also check your typical and peak pressure balances. You don't want to be pulling air through the walls or ceiling.

Seriously- you insulated without air sealing first? If this was a DIY, chock it up to newie error, but from a pro that would be practically criminal, especially for lighting fixtures not rated for insulation contact!

Scoop the insulation away from the fixtures, and used housewrap tape to seal up some cardboard boxes big enough to fit over the fixtures with 3" of clearance (both top & sides), then foam-seal the box to the ceiling gypsum and around where the wiring passed through the box for an air-tight fit. You can then put the cellulose back, even mounding it up a bit over the box.

If you are getting dust throughout the house, then also check the return ducts for sealing.

Posted By Dana1 on 11 Oct 2013 11:07 AM
Seriously- you insulated without air sealing first? If this was a DIY, chock it up to newie error, but from a pro that would be practically criminal, especially for lighting fixtures not rated for insulation contact!

No, I did not build this house.  I am going to determine if the the lights are IC or not. If they are, I am going to foam around the lights then bury in insulation.  If not, I will build a box and put around them. In any case, I will replace the incandescent bulbs with LEDs to cut down on heat generated. I have been putting off changing the bulbs because I have 13 can lights and most are on dimmers and I was avoiding the expense until the price came down to a more reasonable level.

If there is big enough air leakage through them that cellulose or fire retardent is coming through, it's highly unlikely that they're IC rated. When air-sealing them it's worth pressurizing the house with a large window fan or something to hel find any leaking seams/holes.

Maybe get a smoke pen too.

I doubt that the cans are the source of enough air movement to make the cellulose migrate that much unless you have the doors and windows open on a windy day. I'm think from my past insulation jobs that it is either continuous soffit vents or gable end vents or both. Either way seal the cans and get a garden pump sprayer and lighlty coat the surface of the celly so that it just turns a little darker gray. This will glue the paper pieces together. Used this trick for years and never had a problem with migration.

I found these recessed lighting covers made by Tenmat which look fairly simple to install and will probably go this route.  You put them over the light and seal the bottom with insulating spray foam.  It looks like you can order them online at Amazon or Home Depot for around $15 - $18 depending on the size.

http://www.recessedlightcover.com

Posted By smartwall on 16 Oct 2013 09:23 AM
I doubt that the cans are the source of enough air movement to make the cellulose migrate that much unless you have the doors and windows open on a windy day. I'm think from my past insulation jobs that it is either continuous soffit vents or gable end vents or both. Either way seal the cans and get a garden pump sprayer and lighlty coat the surface of the celly so that it just turns a little darker gray. This will glue the paper pieces together. Used this trick for years and never had a problem with migration.

Houses with leaky ducts and air handler in the attic can easily provide enough air flow to drive insulation and fire retardent through leaky recessed lighting cans.  (That would also be a condition worth remediating.)

In otherwise pretty tight houses, running exhaust ventilation or clothes dryers can suck in a substantial fraction of the exhaust air volume through the fixtures too.

These scenarios are pretty common causes of irritant aerosol glass particles showing up in the indoor air when fiberglass insulation is in the attic. While the cellulose & borates won't hang in the air the way glass micro-fibers can,  it can an does get moved this way.

Sorry misread the post, but try the water spray it will keep the stuff from moving. As far as covers try jrproductsinc.com it's where I buy my insulation related goodies