sealing up ceiling from attic

What kind of material would one use to seal off a lowered ceiling area, used to fill in the area between the top of kitchen cabinets and the ceiling, also used for housing a recessed can light for the room,,,it needs to be sealed inside the attic so blown in cellulose won't leak through the can light back into the house.
Preferably a fireproof or retardant material (no foamboard etc.).
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<< What kind of material would one use to seal off a lowered ceiling area, >>
How about a spray foam? There is a choice of rigid or flexible depending on whether the expansion could cause any problems. HTH
Joe
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They should have used a scrap of drywall when they boxed in the soffit. Since they didn't, the easiest thing to do is get in the attic and lay a piece of 1/4" Luan or other light floor underlayment on top of the ceiling joists and then box the open ends of the joist cavities with pieces the same stuff and use duct tape or light brads to hold it in place. There are commercial foam applicators that work more like caulking than the cheap foam crap you buy at the store, but since you probably don't have one I'd just use painter's caulk to seal the joints to keep out drafts. Unless you have an applicator, foam just makes a huge mess in this application. Have them blow a little extra insulation in this area to accomodate the loss of depth.
The other option if your canned lights can handle close contact with insulation is to cut "bricks" of 6" insulation (where a brick is like 10 feet long and 18" wide) and fill the soffit cavity from above up to the height of the ceiling. If you do this make sure you check requirements on the cans for clearance.
Sam wrote:

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