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Question DetailsAsked on 9/22/2012

Is it necessary to remove old fiberglass insulation in attic before blowing in new cellulose insulation?

I live in a colonial home that was built in 1967. Here in central Connecticut, we get warm summers and cold winters. Our attic has what looks like just a couple inches of old, settled blown-in fiberglass insulation. I was going to buy new insulation from Home Depot and rent a machine that blows in Atticat Loose Fill Blowing Insulation. I wanted to get it up to an R50-R60 with that product.

I am wondering if I should hire someone to come and remove the old insulation first (it could have mold in it, but I didn't want to rustle it around too much and release any pores if it was in there). Or, is it okay to just blow in the new insulation right on top? I suppose the other added bonus of removing the old is that I could ensure the vents are all free of clogs, etc.


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6 Answers

Voted Best Answer

Steve made a good point. Also, while it isn't required to remove the old insulation you can check the ductwork, wiring, etc. with the old stuff removed, You can also spray foam around all openings and holes in wall top plates to better seal your home as Steve was pointing out. My concern is the potential for mold spores you mentioned in your question. If you suspect there are any get a good company in to remove the old and clean the attic. Another concern is asbestos. Your home is old enough you could have it in there and that's worse than mold if released into the air.

Todd Shell
Todd's Home Services

Answered 8 years ago by Todd's Home Services


Remove the old. Go to and you will learn the importance of air sealing your home and attic. If you go outside on a cold and windy day with only a sweater, the cold air will eventually blow through the sweater and you will be cold and uncomfortable. If you put a wind breaker over the sweater, you'll stop the air infiltration and stay warm. That's the importance of air sealing and the only way to properly air seal your home is usually to remove the old insulation.
Steve Anderson, Progressive Insulation & Windows: Chatsworth, CA

Answered 8 years ago by Steve Anderson


Thanks, guys. I will plan to hire someone to remove the old, and then i'll spray around any of the openings prior to blowing in new.

Answered 8 years ago by AJRinCT


Be sure to check Angie's List for a highly rated company in your area to remove that old insulation.

Answered 8 years ago by HughV


Sorry I didn't reply sooner,use plastic rake to move existing insulation around so you can air seal the floor of the attic, Highly doubt any insulation you have would support mold. Put cellulose as a cap over old insulation. I was an energy auditior and weatherizer 20 years ago,, so I know from experience. Consider the new fashion radiant barriers when in the attic, see my blog for info.
Jim Casper
40 Year Home Improvement Contractor


Answered 8 years ago by jccasper


If the existing insulation is not contaminated with mold or animal xxxx /urine, it can be raked aside and blown over as mentioned above.

Definitely air seal along with the insulation.

Answered 6 years ago by WoWHomeSolutions



Answered 5 years ago by Guest_92612071

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