Attic insulation - cellulose or fiberglass?


Old 01-11-09, 07:56 PM
Thread Starter
Join Date: Jan 2009
Location: Louisiana
Posts: 1
Attic insulation - cellulose or fiberglass?


Im new to this forum, this is my first post, and I apologize for the fact that its a long one.

My wife and I have a 35 year old, 2200 square foot, ranch style, single level house, with a hip roof, with a 6-12 pitch. We live in the south. We currently have about 4 to 5 inches of blown-in rock wool (I know, they no longer use that type) insulation in our attic. Wed like to add another 12 inches of blown-in insulation. We dont want to use batts, because no one in our area installs batts, and we dont want to do it ourselves.

Our question concerns the comparison of blown-in fiberglass versus blown-in cellulose. We have read (on the web) that cellulose has a lot of merit, and according to some things that weve read, is superior to fiberglass, but since we dont know anyone whos used cellulose, we have no way to compare it. The insulation contractors that weve spoken to in our area indicate that they can blow either cellulose or fiberglass, depending upon our choice.

Can any of you help us with this decision? Wed appreciate any input from those of you who have experience with either cellulose or fiberglass or both.

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Old 01-12-09, 04:14 AM
Join Date: Feb 2006
Location: New York
Posts: 174
Seeing as what we do is new construction, I don't get into blown in insulation at all. The insulation contractors you have spoken to said they will do whatever you want, I would ask them what they recommend and compare the prices. I can't see that one should cost much more than the other. Ask about how each holds up to moisture, etc.
Old 01-13-09, 06:26 PM
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Join Date: Feb 2006
Location: Williamsport
Posts: 713
First, I have to say is Cellulose is GREAT insulation!! You can do this yourself!! It is not hard at all!!!

We have a house that we bought in 2005, it had NO insulation anywhere!! So that was my first project. I was 25 yo then! I did it with the help from a friend. We rented the machine at lowes and I bought 15 bags of cellulose. So I went to the attic, cut about a 15inch wide strip of the floor up down the center, shoved the hose down each section between the joists and filled it up!! Since you just wanna add this, I take it there won't be any cutting or anything. Just becarefull not to block any vents(soffit). Trust me a monkey could do this. If the time is a factor in your lives then I understand.

I also did my exterior walls in 2006. I noticed a big difference in the temp and in sound proofing. When cars go by they aren't so loud. I live in North central PA! So it gets cold up here. Gonna be single digits here by the end of the week.

I did get a quote from one contractor up here and he recommended cellulose over fiberglass(blown in) and to do the attic and walls it was going to cost me about 2800 bucks!! I said thanks for stopping by!! I spent for both walls and attic just under 700 bucks. That includes the 2 cases of beer for my friends, and the rental of the machine!! You can also get it at Home depot!!

I hope this helps in your decision!! Good Luck and keep us all posted!!
Old 01-13-09, 06:43 PM
Join Date: Mar 2005
Location: USA
Posts: 6,126
Attic insulation - cellulose or fiberglass?

Cellulose is far superior to fiberglass in terms of insulation, fire and mold resistance.

Rock wool and it similar products is still used because of its superior peformance in certain applications in addition to insulation.

Addition - After looking at several hundred homes in MS and LA, after Katrina and Rita, I saw many homes that had collapsed interior ceilings due to the ability of the fiberglass to to hold (not absorb, but hold enough moisture/weight) - the moisture from being in 12" of water above the floor for a period of time. Fiberglass just never seems to dry out and will hold and permit the growth of mold. - the walls were automatically stripped and renailed and replaced with good insulation.


Last edited by Concretemasonry; 01-13-09 at 06:51 PM. Reason: Addition
Old 01-16-09, 07:46 AM
Join Date: Oct 2008
Location: St. George UT
Posts: 10
Cellulose is a superior insulation to fiberglass hands down!!

One thing I would suggest is to always buy insulation by R-Value, Not inches. For example if you specify you want 12 additional inches, Cellulose would have be about R-42 to R-45, where 12 inches of blown fiberglass is only about R-30. This is considering if 12 inches is the settled and not depth or what is initially blown.

Specify that you want at least the minimum amount of bags installed for the rated R-value. BAG COUNT IS IMPORTANT! and required by law to be stated on the certificate, along with sq. footage covered, depth, type, brand, signature of installer and date (get a copy of the bag chart printed on the bag before the job, do the math for the bag count*...and then ask the installers if they can tell you the sq. footage and the # of bags they are going to use, if they can't answer these questions...Get a different contractor or at the very least tell them they need to find out and give you the correct answer before they start.....don't be afraid to count the bags going into the machine, It's your money.

*easy formula for determining bag count
(SQ FT) X (pounds per sq.ft.) / (weight of bag) = correct # of bags.

for your house R-38, >> 2,200(sf) X 1.355 / 30 = 99.4 bags

Example is for the type we use, this info is found on each bag and/or the certificate (Attic Card)>> (Manufacturer: Green Fiber "Cocoon" Cellulose. Item # INS510LD 30 pound bags) these figures very from type and brand used.
Old 01-19-09, 02:59 PM
Join Date: Jun 2008
Location: Fort Worth,Texas
Posts: 36
Everyone here has the right idea about cellulose, it is a much better product for insulating attics. The other benefit is that much of the cellulose used for insulation is also made from recycled material, so you are being green also. Make sure that you keep your receipts for the materials that you buy because the government passed a law saying you can get a tax credit for adding insulation (among other things) to your home to make it more energy efficient.

Go to for more details but the basics are that you need to keep your receipt,and the manufacturers certification statement and you can get 10% of the cost of the insulation, up to 500.00 dollars, this does not include the cost of installation but still it is a tax credit, so it comes right off your taxes. It is a great way to save money and make your house more efficient.

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