# OK to fill this lowered ceiling cavity with cellulose?



## MikeMKE (Mar 13, 2014)

This is a lowered bathroom ceiling. I've popped up all of the floorboards & moved them out of the way. My thought was to blow cellulose into this area, up to the top of the joists, then replace the floorboards & roll fiberglass over top. The deepest part of this lowered area is 18" from the top of the joists. That seems like a lot of cellulose & I'm concerned about the weight on the ceiling. The drywall is 1/2", and the framing members that run parallel to the joists are 1x1s. The vent fan is IC-rated. There is also a recessed light not shown in the picture that is IC-rated and stamped airtight. Would it be ok to just fill this cavity with cellulose and be done with it (after I add soffit vents & rafter baffles)? Any advice or other suggestions would be greatly appreciated!!


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## Windows on Wash (Aug 30, 2011)

Should be okay but why do you need 18"

I would still box out the can light regardless of rating. You have done a great job by the looks of it with everything else.


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## joecaption (Nov 30, 2011)

You can do that but by the looks of it those joist are not even close to being wide enough to be used as floor joist.


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## MikeMKE (Mar 13, 2014)

Windows on Wash said:


> Should be okay but why do you need 18"


Good point. Would it be ok to have a gap between the top of the cellulose & the bottom of the floorboards if I'm rolling fiberglass over the top of the floorboards?


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## MikeMKE (Mar 13, 2014)

joecaption said:


> You can do that but by the looks of it those joist are not even close to being wide enough to be used as floor joist.


Nothing will be stored in the attic, so I don't know if you can really consider it a floor. Other than the fact that it has floorboards on it...


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## Windows on Wash (Aug 30, 2011)

If you got 13-14" of insulation, skip the insulation on top of the floor boards completely.


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## MikeMKE (Mar 13, 2014)

Windows on Wash said:


> If you got 13-14" of insulation, skip the insulation on top of the floor boards completely.


In the majority of the attic there's only a 4" gap beneath the floor boards, so I'll have to insulate on top there. Seems weird to have insulation rolled over the floor boards everywhere except one small area, but oh well. I think I'm just over-thinking things now


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## Gary in WA (Mar 11, 2009)

Cellulose can add up quickly; https://docs.google.com/viewer?a=v&...xf51fE&sig=AHIEtbQixCH3AO0RugCGh3VLQNBaXp54rA

OTOH, depends on the brand, if topping for settling (so no air gap to deck boards for currents) you may be at the ceiling drywall limit (check #s of your brand) eg.; http://www.greenfiber.com/step_one_-_calculate_your_need_how_to_install.html

Air seal the attic first, especially at the wall/ceiling drywall joints- as you did fan housing- canned foam; http://www.google.com/url?sa=t&sour...sg=AFQjCNHwd56o0AxLi8-V03E5cMUmwWATQw&cad=rja

IMO, change the flex duct from fan to rigid pipe, insulate around it, have positive drain (slope) to exterior hood. May find existing with water in it as uninsulated now... fire-block the gable studs (at joist level) as appear balloon framed, if adding R-19 (low-density) batts, add a housewrap to prevent wind-washing from inherent gabled attic air convective loops.

Gary


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## Fix'n it (Mar 12, 2012)

i bought air tight cans. they ARE NOT air tight. there are little holes all through them.
i used automotive high temp silicone to seal them up. and i didn't box them, though i only use LED's in them. any other bulbs i would have boxed them.


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