I'm currently deciding between either using blown fiberglass or blown cellulose and have been told very different things concerning which is the best to use. The cellulose apparently has a moisture activated glue that helps it adhere to the walls when it's blown. Which is best in terms of R-factor and longevity?

There are two type of cellulose. One being a kind that is wet sprayed on the wall and the other requires putting a vapor barrier up first then pressure blowing it into the wall. If you don't pressure blow it(the dry cellulose), it will settle.

-Cellulose is more fire resistant that fiberglass. Fiberglass also melts which leaves a nice hole for a fire to extend through.
-Fiberglass is known to cause cancer. The dust from the cellulose is known as a nucience dust and isn't known to have any health concerns.
-Most cellulose is a insect repelent because it contains boric acid(used as a insecticide). I've also *heard* it repels rodents too because it hurts their eyes but I don't have anything to back that up.
-The R-value of cellulose is about 3.8. The R-value of fiberglass batts isabout 3.4
-Cellulose controls air infiltration about 40% better than fiberglass. It will also fill up all the nooks and crannies. If you've ever seen fiberglass installed, they can never get a tight fit around outlet boxes(or even on the smooth wall surface!) so there are lots of leaks with fiberglass.
-Cellulose will retain its R-value to as low as -40F. Fiberglass will retain 60% of is R-value at that temperture.

There is a lot more information about cellulose on our website listed below. Yeah, it sounds like I'm promoting cellulose because thats what we install and as far as im concerned its a much better investment. There are some benifits to using fiberglass like if you ever have to remove a ceiling, the fiberglass won't fall out at you BUT you can put the cellulose in bags and reuse it. Cellulose is more expensive but you can save up to 40% on energy cost vs. using fiberglass so it will pay for itself pretty quickly. Like I said, there is a lot of information on our site.

Thanks for the information. I spoke with a contractor last night who swore by it also. The individual who would be installing it for me uses a wet-sprayed method. Sounds like this is the best way of installing it.

How does one achieve a vapor retarder with blown-in cellulose? How does fiberglass insulation which is contained within a wall cause cancer? The difference between R-3.4 and R-3.8 is about 10 percent...how does that equate to a 40 percent savings? How often does it get to -40F, and what is the difference between cellulose and fiberglass in the normal temperature range of use? There are simple steps that can and should be taken to control air infiltration and insulate around electrical boxes, etc., no matter what insulation is used, no?

The answers to these questions are vital in making a true comparison, and a sound decision.

This message has been edited. Last edited by: Richard Hetzel,

All my information is from studies that have been done and not my own assumption of what I think. The fiberglass is know to cause cancer(primarly when being installed?). Cellulose isn't. Just stating a fact.
I also said it controls air infilration 40% better than fiberglass, not saves 40% more energy cost. It, however, will save up to 26% on energy cost vs. fiberglass. We use a poly plastic called parPac which is the vapor barrier which also contains a cord running through it like chicken wire so when you pressure pack it, it won't bow too much. When you blow the cellulose, it fills up all the holes(everything!) so it doesn't leave air leaks like fiberglass. Why go through the extra hassle of adding extra stuff to help seal leaks when you could have taken care of it in the first place? I'm not sure if you have seen blown in cellulose installed but if not perhaps you should call a local installer and ask to watch them(don't mean that to be a rude comment if it seems that way).

As for the fiberglass losing its R-value, that was for blown in fiberglass, my mistake. But heres the info on that: Performance and Safety

In reference to Adam B comment above, fiberglass insulation used for home insulation is not known to cause cancer. Since 1988, it has been listed on the International Agency for Research on Cancer (IARC) as a POTENTIAL carcinogen (Group 2B), then recently downgraded in 2005 to Group 3 (not classifiable as to carcinogenicity to humans)-- in other words, it is nothing more than an irritant. More information is available at http://monographs.iarc.fr. Most fiberglass manufacturers post asbestos litigation closely monitor biopersistence of their product so as not to endanger humans.

It's best to get facts straight if you want to maintain credibility.

Credibility apparently doesn't sell cellulose.

quote:

Originally posted by Ken F:
In reference to Adam B comment above, fiberglass insulation used for home insulation is not known to cause cancer. Since 1988, it has been listed on the International Agency for Research on Cancer (IARC) as a POTENTIAL carcinogen (Group 2B), then recently downgraded in 2005 to Group 3 (not classifiable as to carcinogenicity to humans)-- in other words, it is nothing more than an irritant. More information is available at http://monographs.iarc.fr. Most fiberglass manufacturers post asbestos litigation closely monitor biopersistence of their product so as not to endanger humans.

It's best to get facts straight if you want to maintain credibility.

It appears you are right. But reports about things like that change all the time and I wasn't aware of it. Am I expected to go check them every time I want to post advice for someone? And credibility isn't an issue because I wasn't trying to mislead you. If you see someone make a error then go "Oh no! I don't want to take anything else s/he says into account!" then thats your choice but a stupid one. I'm only human, as the other people on this site who try to help people.

Chris - we also had the same question about doing our attic ... blow cellulose or blow fiberglass.

I did some research online and found too many "stories" about cellulose (and all the chemicals in it) making people sick. Airborne fiberglass "dust" can lodge in lungs and be an irritant, but this is only a concern during installation.

We ended up going with fiberglass for what it's worth.

Good luck with your decision!
(Incidently, if you're talking about walls, I'd recommend the spray foams - much better blockage of air infiltration.)