blown-in cellulose vs. blown-in fiberglass

[chomeur]

I'm thinking of insulating my 1850's house with blown-in cellulose -- dense-packed in the walls and loose to R-50 in the attic floor. I've been getting estimates and most people I've talked to think my plan is fine. But one guy says he would recommend blown-in fiberglass rather than cellulose, because he has "had good experience with it". Can anyone tell me the pros and cons of blown-in cellulose vs. blown-in fiberglass?

[Jackofalltrades]

Blown Fiberglass
R=2.2
does not stop air flow
does not seal tiny gaps and holes
possible carcinogen - per manufacturers required labeling
decreased R value by almost 50% as temperature drops to -40 degrees F (when you need it most)

Dense Pack Cellulose
R=3.7
greatly reduces air flow
seals all tiny gaps and holes
boric acid fire retardant is harmless - has been used to treat pink eye for decades
maintains R-value to -40 degrees F

[robhelms]

One thing to be careful about when posting information like this is to make sure that you are accurate. I say this not to be argumentive, but to be clear. I to am a fan of cellulose and we install a lot of it, but to claim that fiberglass is lower in value on a dense pack it to go against published information. The following is from a published document from the industry. The organization is the NAIMA, and while that is fiberglass industries association, the information and test data is well documented.

Thermal performance Blown in Ranges:

Fiberglass Cellulose
2x4 walls R 13 to 15 R 12 to 13
2x6 walls R 20 to 23 R 19 to 20

I have been in the industry for 35 years, and i have alway thought that overall Cellulose does a better job, but it is important to be correct. I also know that fiberglass by nature is a very good insulation when installed properly. Cellulose according to it's own test data does not begin to exceed fiberglass until the depth of it reaches in the R 22 to 25 range, and in fact in attics at lower depths like R 11 to 19 it has a tad lower effective range. It is the density of the fiber that grows expotentially as more is applied that causes the product to outperform fiberglass.

There is a lot of talk on the internet about a batt have very low R value. That is true when old school install methods are used. and the new energy star method is not invoked. Spliting around pipes and wires, and making sure that the batt is installed to touch all air barriers in vital. Once that is done the R value is far more in range with the tested norms. This does not come into play with the project in question above, but i mention it for information purposes.

The real area where Cellulose excels is that it is somewhat easier to install in a closed wall blow situation due to the smaller nature of it's fiber. And it's high air flow qualities as was mentioned above.

[SIM]

Rob, I appreciate the tone and detail in your post.

Do you have any sources besides NAIMA that support these reported R values in real life situations for blown in fiberglass? I'm curious to know how glass could insulate so well when being blown into a cavity that is literally out of sight of the installer.

[robhelms]

rhi, Thank you for your response. I appreciate the opportunity to enter the dialog. I have been in the industry for many years, and have been active in both the fiberglass and cellulose fields. I always try to present to the customer a fair and true evaluation of their needs. The NAIMA website lists the studies completed to support the data presented in detail, the list is long. I am in no way trying to argue against Cellulose, as I truely believe it is a very solid product. I am trying to eliminate bias from the discussion. I would ask in return for data that disproves my comments. Your question implies that there is a problem since fiberglass is blown out of sight, or blind was we say, but in reality ALL insulation that is dense packed in a closed wall is blown out of sight, not just fiberglass. I have seen both blown on many occasions, and one process our company does is dense packing behind mesh on new construction, both fiberglass and cellulose, This is a process that allows one to study the charactaristics of the materials being used to a reasonable degree, since they are more visable. While the cellulose tends to go in a tad easier the fiberglass has less tendancy to settle, and actually goes in and packs right nicely.

To me this shows both products have some very positive qualities. In a dry dense pack situation the Cellulose industry itself only claims to reach a R 12.6 in a 2X4 wall, but the fiberglass industry can attain an between a R 13 and an R 15 in the same application. These ratings for both products were attained by third party testing, and are standards of the industry. In recent talks with one of the major cellulose manufactors i was told they are striving to attain a true R 13 in that application. The fact that they publish this data themselves add credence to the rating system.

I want to stress that i offer this information, fully believing that cellulose is the answer to many problems in field especially the retrofit market. But i find it to be the responsible path to make sure that the data is presented as fair as possible, so the consumer can make a choice based on fact not propaganda. There is enough of that in the building trades already. Again thanks for the open forum dialog, i appreciate the opportunity to talk with other professionals in our field that care about the end results.

[Jason Stoller]

NAIMA is not a good source of information as it is an arm of the fiberglass insulation industry. Their web site states

A quick glance at their web site reveals a most incomplete set of articles. They leave out pertinent information related to their fiberglass products to keep the consumer from making the best choice, even though they repeatedly address the supposed deficiencies of cellulose and other insulation products.

For example, I can find no reference in NAIMA's installation explaining the pressure at which it should be installed in a wall cavity. I can only guess that the reason is because fiberglass is a poor material for this type of application.

Being glass fibers, you can't dense pack fiberglass into wall cavities because the R value is greatly reduced (solid glass is a terrible insulator), and there is little to no air sealing ewffect. Yet someone in the insulation business for only 1 month knows that you lose a lot of energy through exterior walls if the walls can't be air sealed before or during the installation of the insulation material. As a result, the appropriate material to install is cellulose at a density between 3.5 - 4.0 lbs-cu-ft with a tube that is inserted the entire length of the wall cavity. Using a dense pack tube assures that the insulation material won't get hung up in an irregular cavity such as those with electrical wires. Equally important, installing the insulation under pressure allows it to pack into small openings and seams that are inevitable and numerous in retrofit applications. Again, you can not achieve this with fiberglass - its just a poor insulation material for this important application.

Finally, the R-value of fiberglass is greatly reduced when there is air flow through it.

In summary, fiberglass is a poor material to use in wall cavities of existing homes because fiberglass cannot be adequately placed in the entire wall cavity, fiberglass does not stop air flow in the cavity, and the R-value of fiberglass is greatly reduced when air flow is present (all retrofit homes).

[Jackofalltrades]

Hey Rob, sounds like you know a lot about all types of cellulose. I am getting confused here so can you explain how blown in fiberglass compares with dense packing cellulose into an older homes exterior walls? I have an 80 year old duplex with nothing in the walls. I will be residing this spring and want to insulate walls ASAP. The local contractor says fiberglass is just as good but I just don't see how it can get everywhere and I do understand that you can't blow it in hard like you can cellulose. Also what about the tube that goes everywhere in the wall as opposed to these directional nozzles that simply point up or down? So if it were your house what would you do? Thanks in advance!!!

[robhelms]

Jason, i appreciate your comments, but still there are stats on this listed at that site, as well as research articles on the subjects. First, just because you say they are incomplete does not prove your point, since someone else could say the same about Cellulose. Most of the information from the cellulose industry comes from, ..... you guessed it the cellulose industry, so sure all of the industry is replete with propaganda. I would ask, why do they get a free pass on this, where the fiberglass industry does not? A couple times in your statements you said " My guess is" That is the problem with this type of discussion too much runs on guesswork and conjecture, or at the least personal viewpoint, and what product we are marketing our business for. Secondly, fiberglass has been densed packed for decades, ever heard of the BIBs system? We have a branch office in Washington State, and it uses this type of process with both fiberglass and cellulose, and the R-Values for both are well documented from studies done by third party testing facilities.

A good example of the challenges that the cellulose industry faces is in the area of wet or wall spray application. The manufactures claim this is the best application of their product. The rate it higher than dense pack. But it has many weaknesses. 1. if you don't have just the right water level, humidity, and pressure it will not stick and can fall out. During the day change temperature and humidity level can change the application dramatically. Moisture can be retained far longer than the maker admits. Chemicals can cause some corrosion, even more than they admit to. Anything over 2x6 walls and the problem begins to get worse. Add to that the fact that in an attic blow it is suggested that water be added to stabilize the material so as to limit settling after the fact. Many out there do not properly use the water, so settling does occur. This is an issue that cellulose has, but that does not make cellulose a bad product. It means it must be handled properly, and the installer must have the proper equipment to do it right.

As far as the idea that fiberglass will not resist airflow, keep in mind that many of these test devices that permiate the industry are marketing ploys, and are designed to exploit the weakness of the enemy, and magnify the hometeam. To take a air blowing device and blow air up in a wall thru a product is not a real world test. First airflow thru a wall is not under pressure it is usually a drafted air situation and has no real pressure behind it, so the test is not applicable to actual in home situations.

Lastly I am in no way an advocate for the fiberglass industry. In our branch, where we regualrly employe 10 to 12 installers even in these times we use both fiberglass and cellulose. In fact we are currently moving a large quantity of cellulose each month. In a dense pack retrofit wall i would suggest Cellulose for a few simple reasons, the No. 1 being i feel it is a bit easier to install, and gives a very good result.

Then main reason i posted in the first place is that i wanted to go on record as saying that it is not a good idea to make blanket statements that one type of material is no good when it has been proven to work over a long period time. I believe there is two sides to this discussion, and we should be fair to the whole industry, as it has been good to us.

[robhelms]

Interesting information to add to this discussion. http://www.specjm.com/products/sprayin2 ... ndfill.asp The information on this page is certainly from JM, however there is some very compelling information. Take a look at the third party testing PDF. It directly addresses the air flow testing done for JMs Spider product.

[Energy Man]

Geeezz, that is an interesting product and aggressive marketing by JM, but the supposed 3rd party independent research is just bad science. I mean come on, look at the cellulose in that test equipment. It looks like marbles, not cellulose!!! This is junk science and the entire informational brochure is unfortunately meaningless.

Quality cellulose appears much more uniform, almost a solid gray. Here's the pic - click to enlarge!