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Remove or cover over old insulation

pizza's picture

Hi. A friend of mine was wondering whether he should remove the old fluffy gray loose insulation in his attic before blowing in new insulation. Or can the old stuff be allowed to stay and just blow in the new stuff right on top of it. He says he believes that old stuff is original to the house which was built in the 50's.

I thought I'd ask the experts here. Thanks to everyone in advance!

So long as you are confident (post #184096, reply #1 of 5)

So long as you are confident that there are no airspaces below the old insulation(black blown-in....probably rock-wool) blow the new right on top...However, great care should be taken to airseal before you add anymore insulation...fill all penetrations with foam or caulk or tremco(acoustical sealant). If you skip this step, you almost shouldn't bother with more insulation...

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If that fluffy grey stuff is (post #184096, reply #2 of 5)

If that fluffy grey stuff is vermiculite, you might want to get it tested for asbestos.

Otherwise you should seal all holes leading to the attic (wiring, vents, etc) with spray foam, then cover with new insulation.

Adding new insulation without sealing the holes first will lessen it's effectiveness. You might as well just throw 25% of the new insulation in the dumpster.

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>>If that fluffy grey stuff (post #184096, reply #3 of 5)

>>If that fluffy grey stuff is vermiculite, you might want to get it tested for asbestos.

So far as I know, EPA is still recommending encapsulating/covering vermiculite attic insulation.

And recommending against such testing: "Currently, there are specific technical issues involving vermiculite sampling that can complicate testing for the presence of asbestos fibers and interpreting the risk from exposure. EPA and ATSDR are not recommending at this time that homeowners have vermiculite attic insulation tested for asbestos. As testing techniques are refined, EPA and ATSDR will provide information to the public on the benefits of testing that produce more definitive and accurate test results."

I've been following this issue for a long time.

Reading between the lines, I get the impression that the levels in "contaminated" VermIns are so low they are really hard to detect.

NOTE: that isn't much more than an impression and barely rises to the level of a 'tentative opinion.'

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Good to know - thanks! (post #184096, reply #4 of 5)

Good to know - thanks!

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Generally you'll do fine (post #184096, reply #5 of 5)

Generally you'll do fine putting new insulation over the old. The old stuff may compress somewhat, but it still provides insulating value.

If the "fluffy gray loose" stuff is really fluffy and soft then it's likely cellulose. If it's a bit gritty then one of the vermiculite varieties, probably, or possibly rock wool.

The danger with old insulation, as stated, is that it might contain asbestos, and by covering over you could compound problems should it need to be removed in the future. But even if it does contain asbestos, if it's covered and left undisturbed then it's not going to hurt anyone and there should be no need to remove it -- it's more hazardous to remove it than to leave it be.

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