My basement shop area currently has open floor joists above it, with insulation batting between them. (Yes, I know current theory says insulating there is of minimum value, but for sake of discussion ...)

Hand tools, and even small power tools, don't throw enough dust that I've had to worry about this. But as I scale up and start to get more serious about dust collection, it occurs to me to wonder...

How much risk is there of enough sawdust settling in that insulation to compromise its non-flammability? Do I need to speed up the decision about whether to install a ceiling or remove that batting?

(I suppose I should note that the insulation in this case is a fireproofed cellulose -- the batting equivalent of blown-in. Much more pleasant to work with than fiberglass.)


I don't believe anyone actually tested how sawdust contamination affects flammability of glass-wool or cellulose insulation.

Just installing a vapor barrier on the bottom will help prevent dust accumulation on the insulation.

  • It'll also affect how vapor escapes a potentially damp basement, which could result in condensation and mold. Putting up sheetrock would be a safer, though more expensive and intensive, option. – coreyward May 10 '15 at 18:54
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    @coreyward Adding a vapor barrier will only affect the basement moisture noticeably if the homeowner already has very significant moisture problems. Mitigating the moisture issues should be first on the list - not worrying about getting sawdust in the insulation. In other words, if they are not already dealing with bad moisture problems, then adding a vapor barrier will do little to change the situation, and they probably won't have to worry about them after the vapor barrier either. – Adam Davis May 11 '15 at 12:39
  • @AdamDavis buildingscience.com/documents/digests/… – coreyward May 11 '15 at 15:37

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