Blown Fiberglass or Cellulose?

[leeklm]

Going to blow insulation for the 1300ft garage ceiling... I have worked with cellulose in the past, but not fiberglass.

Any thoughts from guys that have used both?

Thanks!

 

[rlitman]

Cellulose. It insulates better, it's more fire retardant and insect repellent, and none of those nasty fibers. Also, it allows for less air infiltration, and settles less.

Just one thing they don't tell you. You may get an ammonia smell for a couple of weeks after spraying it.

 

[haugy]

Weight is the only advantage fiberglass has over cellulose. It's lighter. Which for me with the way my ceiling was designed is why I have to use fiberglass. Whee.

 

[Ittledoo]

I am biased considering I work for an Insulation manufacturer. But I would have to disagree with the earlier post. Now, I have not dealt with insulation before I came to work for Knauf Insulation so what I know has been from this company, but there is an awful lot of studies to say that actually fiberglass is better and safer product for the money. Cellulose settles down 1/3 the rate of blown fiberglass, at least our product. Also both have the same element in it for fire retardation, but considering our binder content, we do not need to add the same amount that cellulose needs to. Which that chemical is toxic, contrar to the advertisements. I would also suggest, if this is a new build, run sealant around all of your cracks to drastically increase air protection.

Regardless who/what you go with definitively check out a sealant!

Here are a few links...

http://www.knaufinsulation.us/

http://www.knaufusa.com/products/bu...insulation/knauf_insulati_jet_stream_733.aspx

http://www.knaufusa.com/products/building_insulation/residential_insulation/ecoseal™_sealant.aspx

Knauf is only sold to distributors and contractors, but if your interested let me know and I'd be happy to send you the sales rep info for the Minneapolis area.

 

[54FordPanel]

....Cellulose settles down 1/3 the rate of blown fiberglass, at least our product. .........

Even if it settles down, does that change it's R rating?

I use cellulose, strictly for the reason of working in it later (I tend to get up in my attic alot for some reason) and the comfort of putting it in. I've gotten the rental machine from Home Depot (free with 20 bag purchase) and put in 20-30 bags 4 times in the last 10 years in various houses. I've put 30 bags in this house already, and will be putting 20 more bags in soon.

I hate, hate HATE working in fiberglass insulation.

 

[csp]

Even if it settles down, does that change it's R rating?

Yes it does. Less loft or dead air space means less R-value.

 

[The Outlaw]

Cellulose is actually a slightly better insulator than fiberglass. But It settles a lot more and than fiberglass. Celulose requires a lot more material to achieve the same R value. It does weigh more and since you need more of it to accomplish the same R value that even more added weight.

Both are equally fire retardant as they HAVE to meet certain expectations to meet codes. Fiber glass will catch on fire but at a higher temp than cellulose and will not sustain a flame where as cellulose will. Remember it is pretty much news paper.

Blown in insulation is only intended for areas that will not be access again. Both only work when they are applied as intended. Meaning blown in and not compressed. If you pack it down you actually loose R value. This goes for fiberglass bats as well. Crunching them up and shoving them behind pipes and wires looses R value. Craming fiberglass into cracks will stop air flow but is not a insulator.

But if it is tightly compressed in an area you can build R value. Thus why it is used in retro fitting houses with insulation from the outside. The more you stuff in and tigher packed it is the greater the R value. But for attics this is very expensive as it takes alot more material.

If you plan to use your attic for storage your best bet it to lay down plywood first and then build some wall dams around that area. Compress the blown in material under those areas and do the standard blown-in in the other areas.

The trouble with both these solutions is that they do compress and loose R value over time and as dirty air flows through it and clogs it. Dirty fiberglass does not insulate.

My recommendation has always been to insulate your ceiling is. First foam all cracks and openings like electrical boxes. Then install an R19 bat. I prefer non paper faced bats and then using a poly plastic after for your vapor barrier. Then have a layer of blown in applied on top of that to bring you to R30.

 

[Ittledoo]

I hate, hate HATE working in fiberglass insulation.

One more thing about our product and I will get off the box......we came out w/ a new binder that is eco friendly. Simply eliminated formaldehyde, it is a lot softer and half as irritating as insulation has been in the past. I wouldn't suggest rolling around in it in your shorts, but it makes a heck of a difference.

Outlaw-couldn't have said it better, thank you for the clarification!

 

[JackB]

Can't you get rock-based insulation blow in ? No itching or any of the issues with fiberglass.

 

[Bronson]

I have installed a lot of cellulose in My and My Friends and Families homes. I prefer it just for the fact of later access in the attic means not dealing with that itchy fibreglass.....

 

[leeklm]

Thanks for the replies. Contractor guy at Menards also mentioned that fiberglass settles less, and requires about 1/2 as many bags as cellulose to reach an R38 value. My garage has a hip roof with gable, so does not work well for storage anyway (that part kind of stinks), which means I should have no reason to be up in the attic going forward (at least I hope not). I think my plan is to put up a 6mil vapor barrier, 5/8 rock, and fill it up with fiberglass...

 

[jvitez]

Search the net about R-value loss in cold temps with fiberglass. Modern versions are supposed to be better, but this was still enough for me to spec blown in cellulose for the attic of our house (R-60). I blew around a bit for the first while but the top layer settles and gets a bit of a crust so-to-speak, which then means it's sealed and doesn't blow around anymore.

Cellulose is a great use for recycling newsprint, is equally fire retardant once treated, and probably performs better in cold climates. Making fiberglass uses much more energy, though many have recycled glass in them now. If I had my way I'd have zero fiberglass in my house. Our basement is fiberglass batts, but the main wall are high density spray foam. Mineral wool insulation is far better for walls.

Do the cellulose.

 

[jumpingryan]

My recommendation has always been to insulate your ceiling is. First foam all cracks and openings like electrical boxes. Then install an R19 bat. I prefer non paper faced bats and then using a poly plastic after for your vapor barrier. Then have a layer of blown in applied on top of that to bring you to R30.

I agree with you in the spray foaming of cracks and openings...... and don't forget the baffles for vented attics while you are up there.... every 3rd 24 "inch rafter should do as a min.

For electrical boxes, spray foaming around them isn't always the greatest idea... it can be messy & it can seep in through the small holes in metal boxes, and the stuff isn't 100% fireproof. A lot of spray foam would be required for pod lights that are insulation compatible (and I only install pod lights that are compatible with insulation, even if there is no insulation)

I much prefer those pre-made plastic enclosures for electrical (both boxes and pod lights) on outside walls/ceilings. Tie it into the vapour barrier with tuck tape and you are done.

I have the fibreglass with a layer of blown in on top in both the house and 30?40 garage, and I think that it doesn't really matter what you choose myself. Blown in with batts really makes sealing the gaps in the batts easy.... but for new home stuff.... Get your wiring & plumbing plan right (so you rarely have to go up there again), and just blow it all in and be done with it.

Any batts insulation I put in after renovations is usually mineral wool based, as I like the slightly higher R-value, that bugs, insects & mice avoid it, and it is slightly easier to cut and install (use a bread knife or even a drywall saw)

In Canada (in my area where we see temperatures of -40 C during winter to +30 C in summer) we put the vapour barrier on the warm side, but in certain situations it goes on the cold side if a proper vapour barrier can be achieved. Situations like this include when the building is structured for exterior insulated sheathing rather than wood, and with spray foam applications. Wood sheathing must be allowed to breathe, so in certain buildings, they bump up the structure, omit the outside wall sheathing, and use closed cell foam.

As to attics, R32 is really considered the min these days.... R40 seems to be the standard in my area, with premium homes coming in at R 50 & 60 with really deep blown in heights.

Spray foam & ICF walls are really upping wall insulation in this area as well.

I don't know how vapour barrier would work in the middle of insulation..... mainly because the vapour barrier stops condensation from hot meeting cold, and any air-movement just dirties insulation and reduces it's r-value.

Good

Ryan

 

[Steevo]

I went with cellulose simply because I have a bad reaction to fiberglass dust, and no matter how carefully you plan, a trip into the attic to run a wire, mount a brace, tie in a support or pipe, or something will be necessary. When I do a job in an attic with fiberglass insulation, even with a respirator, for days I feel like my throat is coated with steel wool.

I just had my 24x40 attic blown 18" deep with cellulose.

I paid someone else to do it. That and sheet rock are two things I prefer to have others do.

 

[paullie]

my thoughts on it is the fiberglass type is less dusty and there is no "itch" (at least the pink panther kind i used) it takes more depth of fiber glass to get the same R rating compared to the cellulose and the pink stuff is lighter, over all i liked working with the pink better compared to cellulose , i have really sensitive eyes and had no reaction to blowing pink at all, just my 2cents

 

[Highbeam]

What do you think cellulose is? Do you notice that it iends in "ose". This tells you it is a sugar like lactose, sucrose, fructose, etc. I don't know about you but I don't want an attic full of cotton candy. The bugs love it and it burns despite what chemical sprays may or may not have been applied. Ask a fireman how the sellulose burns, they tell us stories about smoldering cellulose starting fires, called rekindles or something like that.

Fiberglass does not burn. Just try and light it. It doesn't take an additive, it just doesn't burn.

The modern fiberglass is not itchy.

Either one is pretty good, plusses and minuses. You would be a fool to do anything but blown in insulation in an attic these days. Batts are for walls. Really, there is absolutely no reason to waste your time and effort messing around with batts when blowing in is cheaper, easier and will always be superior due to the flowing characteristics.

 

[suprvee]

Cellulose hand down.

It's a natural product (mostly newspaper / paper products mulched with a fire suppressant added), most bugs hate it, mold doesn't grow well on it, and it's safe/easy to work with. You still need to use a good respirator, as it's a very messy product to spray.

 

[richtersrodz]

On my new house build, we wanted to use spray foam. The cost was like $11K, compared
to like ~$2K, blow in. So I guess we will be getting the blown in, since that is what the
budget will allow for.. Haven't asked about what product it will be yet..

 

[BadgerBoilerMN]

Cotton candy, that's a good one. Cellulose is the best value and will not lose up to half of its R-value when temperature dip below zero in a ventilated attic. If you have fiberglass add a foot of cellulose to make it right. All will settle, so put more in!

 

[NUTTSGT]

Use what you want, some hate one and love the other while it's complete opposite for the rest.

Fiberglass, get anything hot enough, it will burn. I can guarantee that if a house ever burned down, which they sometimes can't be stopped, you will not find the fiberglass insulation afterwards.

Cellulose, even with the fire retarders, it will burn/smolder. Every rekindle that we have had, with the exception of one, had cellulose insulation in it. The one exception was one that was started for insurance money.

 

[70chevellegsp]

Fire needs air to burn. Dense packed cellulose doesn't provide the oxygen, while fiberglass is installed loose. There have been tests done on mockup homes with fiberglass and cellulose, and burn times are drastically in favor of the cellulose. It gives you additional time to get out unlike the fiberglass. Cellulose also gets you excellent sound control and less air infiltration. Think about it this way, hot pizza comes in cardboard boxes and furnace filters are made with fiberglass.

 

[NUTTSGT]

Cellulose will also sit and smolder for hours and flare up 4-5 hours later.

Do you know how they test a batch of cellulose for fire retardation ? They take a cup full (off the production line) and stick a lit cigarette in it, filter first. It's only allowed to burn out so far to pass the test.

 

[dlenkewich]

I used to insulate attics for a living.

My opinion - Fibreglass. Light weight, less dust. Contract the job or wear long sleeves, pant's and a dust mask to prevent irritation. I also noted Cellulose being more expensive then fibreglass, the bundle of cellulose was a little bit cheaper but had way less coverage. Your research may vary.

Just to touch on other things that have been said, Fibreglass doesn't loose have it's value in a ventilated attic. It's designed to be in a ventilated attic.

Fibreglass really doesn't like to burn, I know this from 'farm burns'. I'm sure it will burn eventually but it'd be the least of my concerns.

And vapour barrier never goes on the cold side.

"Modern" fibreglass still carry's an itch to it, but it's irritation level depends on the brand. "Old school" insulation is just as itchy as the cheap insulation you can buy today. My recommendation is Johnsmanville and second would be Owens Corning. You can find cheaper product, but you'll pay for it when you're skin's on fire.

 

[54FordPanel]

Has anybody had any real world experience with blown in cellulose causing the drywall to sag?
I've blown in cellulose on all my previous homes, and in this one too. I've been up in my attic enough that I don't have a nice flat blanket of 14" insulation anymore. So I'd like to put in more, to get from about a r-38 to an r-48 or so. So I'd like to add more cellulose, but I've searched on the web and it's recommended that cellulose only be up to an r-38 when used on 1/2" drywall on 24" rafters.
I'd rather put in more cellulose, but don't want my drywall sagging. Can fiberglass be blown in on top of cellulose? And what if I crawl around in it, and mixed all the fiberglass with the cellulose? Does that mess up the r values?

 

[Freefall_Doug]

Brining this back to the top. Does anyone know if blown in cellulose repells rodents.

Previous owner had some fiberglass bats and then some stapled up plastic VB in my detatched three car. The ceiling wasn't finished beyond that point. The top of the ceiling is all decked out as a storage loft, so the bats are in the undersides of the 2x4 joists.

The mice loved the setup, they lived on top of the plastic and under the fiberglass. I bet it was warm and cozy for them. I ripped the plastic down for now because watching the mice scurry was driving me crazy. I have a feeling that if I put drywall up it would be the same situation. The mice don't mind the fiberglass so they would nest on the top of the drywall.

 

[DustynF]

Yep, the stuff I got from Lowes had borax in it to prevent rodents. If you go to the manufactures website they should list if it does.

 

[NUTTSGT]

Yep, the stuff I got from Lowes had borax in it to prevent rodents. If you go to the manufactures website they should list if it does.

Not entirely true, from Wikipedia.

Mold and pest control The borates in cellulose insulation provide superior control against mold. Installations have shown that even several months of water-saturation and improper installation did not result in mold.

It is a common misconception that the mere presence of crude borates in cellulose insulation provides pest control properties to the product. While boric acid itself does kill self-grooming insects if ingested, it must be presented to an insect in both sufficient concentration and in an ingestible form in order to achieve insect fatality. Proper testing of products containing borates must be performed in order to determine whether dosage and presentation are sufficient to kill insects. Once tested, registration with the EPA as a pesticide is required before a product may be touted as having pesticidal capabilities.

Fire retardation The borate treatment also gives cellulose the highest (Class I) fire safety rating. Many cellulose companies use a blend of ammonium sulfate and borate. Although ammonium sulfate is normally odorless, unexplained emission of ammonia and a resulting ammonia smell has been found in some cases.

 

[NUTTSGT]

On a side note for you cellulose insulation users, I'd expect it to start going up in price in the next few years. Since the internet is getting bigger and more media is used online vs. the printed text, newspaper use is going down. This is starting to create a shortage for cellulose manufacturers. Not only is it getting scarce but what they once got for free as a recycleable, they are starting to have to pay for or out pay someone else.

 

[Bent Valve]

R Value?
The fiberglass people invented the test. It is in a sealed box where all products test the same but put it in a place that air can pass through then the R value changes. Foam and cellulose both block air and stay the same R value. Fiberglass lets air flow through(think furnace filter) and reduces R value. Could be only 1/3 of the R value.

 

[wfopete]

R Value?
The fiberglass people invented the test. It is in a sealed box where all products test the same but put it in a place that air can pass through then the R value changes. Foam and cellulose both block air and stay the same R value. Fiberglass lets air flow through(think furnace filter) and reduces R value. Could be only 1/3 of the R value.

AGREED. R Value is a myth. There is more misinformation out there about fiberglass and HVAC in general then almost any other industry (except from your goverment).

But what do contractors say? "That's the way we always done it around here".

 

[Rixter58]

Well, I see nothing has changed since I asked this very same question on this very same forum a couple years back. Evenly divided down the middle. There seems to be no clear answer. Each has its own positives and negatives. In the end I used fiberglass. To the guys complaining about itchyness, I call ********. Insulated the whole damn building, took a shower afterward and never scratched once. To be sure, there are still ways that I would have preferred cellulose. For me, what ended up carrying the day was A. The fact that I am in a pole building and if the roof should sweat from the inside for some reason, fiberglass doesnt turn to paper mache. B. just happened to be at the right place at the right time and scored a great price on the fiberglass. I'm sure either will be fine. Dont overthink it.

 

[BadgerBoilerMN]

My garage has two inches of high density 2# foam covered by 1 foot of blown cellulose. The first thing is controlling infiltration, nothing is better than foam for this critical detail, but you don't have to buy a foot of it.

Thank you for your service Nutts.

 

[cowboybob56]

I live in Red Rock, Az so heating isn't as bad of a problem. The 2012 new 2 car garage w/attached living quarters - 4BR, is finished dry wall but not insulated as usual, (the garage that is). I need to know the particulars of fire barrier boards mid way down and how many holes I will need to drill, more than the celulous/fiberglass dilema.

 

[cnc-me]

What do you think cellulose is? Do you notice that it iends in "ose". This tells you it is a sugar like lactose, sucrose, fructose, etc. I don't know about you but I don't want an attic full of cotton candy. The bugs love it and it burns despite what chemical sprays may or may not have been applied. Ask a fireman how the sellulose burns, they tell us stories about smoldering cellulose starting fires, called rekindles or something like that.

Fiberglass does not burn. Just try and light it. It doesn't take an additive, it just doesn't burn.

The modern fiberglass is not itchy.

Either one is pretty good, plusses and minuses. You would be a fool to do anything but blown in insulation in an attic these days. Batts are for walls. Really, there is absolutely no reason to waste your time and effort messing around with batts when blowing in is cheaper, easier and will always be superior due to the flowing characteristics.

I agree 100%.
After the cellulose has been installed a few years the flame
retardant breaks down and the stuff will burn.
The cellulose also settles much more than the fiberglass, and will
get so hard that you need to rake it to add air.
I personally would not use the cellulose, in an outhouse let alone
anything else.

 

[Falcon67]

Having lived in the country and not having regular trash service, I've tried to burn good size stacks of newspaper. They don't. So packed cellulose would not bother me. However - pricing it out leaves blown fiberglass the winner. Our attic is blown now and I've been up there a lot fixing things. No itch problem. It is easily trampled, so when we blow the garage we're going to blow more in the house. One thing I "figured out" - lol - to make the blow easier is to put 18" pieces of batt at ends of the joists at the walls. This leaves an air gap for flow from the eves and I can blow up to the batt without getting any in the eve areas.

 

[bullnerd]

My garage has two inches of high density 2# foam covered by 1 foot of blown cellulose. The first thing is controlling infiltration, nothing is better than foam for this critical detail, but you don't have to buy a foot of it.

Thank you for your service Nutts.

Was thinking of doing something similar.Not sure if using FG or Cell,will prolly depend on price.

But question is,do I use a vapor barrier under(heat side) of foam or not?

I've seen the comments on here about using foam to control air iniltration and insulation for heat retention.Atic will be full ridge vent and full eve vent.

Steel liner on inside,then foam then blown in?
or
Steel liner on inside,vapor barrier,foam,then blown in?

Thanks for any advice guys.

 

[midwestguy]

First off, Hello everyone! I've been around for a while now, and thought this would be as good as any for my first post. As I work for a State Energy Office for over 20 years now. I started off as an inspector, and now I do most of the training for our state.

One reason cellulose has such a bad rap for settling, is due to contractors and unskilled intallers "fluffing" the insulation. When they blow in the product, they turn the fan on high. Which "fluffs" the product, giving it the apperance that they have installed more insulation than what they really did. Then over the years, due to how the insulation was installed, you have a lot of settling.

Look at it this way. If your a contractor and you bid a job to install 100 bags of insulation. But you "fluff" the product and only install 70. You just saved yourself around $300, with the client not being any wiser as to what you have done.

In our testing, with the products that we have approved though our office, when installed right, settling is limited to about 15-20%. When pricing the two insulations, you need to look at the coverage charts on the bags and compare prices with reference to the coverage rates, not price per bag. While it's almost a wash in price between the two when looking at coverage rates. Cellulose does tend to cost more in the long run, due to the settling.

R value isn't the key, air sealing is. Like others have said, fiberglass is nothing but a filter, as air passes though it freely. This can be shown with a draft meter and blower door, and has been proven in many independent tests. If you have never had a blower door test done on your house, you really should. As it can tell you a lot about your home.

Far as if someone should use a vapor barrier with foam or not, you really should contact you local building inspector. In our state, most of the foams are rated as a class 3 barrier, so for us, it really depends if a class 3 barrier is approved by local codes or not. Many of our local codes require a barrier rated lower than a 3, so again, you really need to check with your local building inspector and see what is required in your area. Calling the foam manufacturer is alway a good thing as well.

Sorry for the long first post, and hope it helps.

 

[JakeKohl]

I chose cellulose for my recent construction project and absolutely LOVE it. I've installed fiberglass before and looked at cross sections of my work. Even though I was exceptionally careful to slit the fibers around plumbing and wiring, it was extremely difficult to get it to wrap around and fill the wall cavity. I seriously doubt many contractors will go to the same trouble I did when I installed it. The cellulose I had blown in was only slightly more expensive than the fiberglass quotes I received and I've found it to be a terrific insulator. I have a friend who is a builder of multi-million dollar homes and he also swears by it.

There is SO MUCH mis-information out there about insulation types and there are so many ways to tilt a test or result. I too was concerned about the fire retardant nature of the various options as well as the nasty chemicals that might be involved. I researched everything thoroughly and mostly discovered that you really need to do your homework to make sure whatever document you are reading is published by an independent party. 90% of everything out there is published by some group affiliated with a particular type of insulation and are skewing their results either through the type of testing method or interpretation of the results.

Someone mentioned that because the word cellulose ends in "ose" means it has sugars in it and they wouldn't want sugars in their walls...this is laughable...the use of the latin "ose" in this case means mostly "possessing" as in "like"....meaning that it is "like" "cells"....cellulose has a cellular structure. "Verbose" doesn't mean sugary language. A lot of sugar type names do end in "ose" but it's not because it defines a sugar....moving on.


With regards to fire retardation, there are a lot of factors that relate to the speed with which a fire travels through a structure. A lit cigarette on a piece of insulation is an indication of the insulation's ability to ignite but doesn't really capture the entire scenario. One of the big insulative advantages of cellulose is that the short misaligned fibers make a dense product that does not let air permeate it easily. Fiberglass, on the other hand, with many of it's fibers aligned in the same direction, will let air flow through it much more easily. Added to which, space around electrical wiring, plumbing, behind boxes, etc. also add to the available air flow. The blown in cellulose is both better at packing in around all of these in-wall features and preventing airflow within its fill. This means you not only get much better insulation value with cellulose, but it's ability to resist air flow within the fill gives you much better fire retardant benefits for the entire structure system. Yes, the charred area left from a blow torch held against cellulose is bigger - but I'm more concerned about how the fire reacts with the entire structure ... i.e., how quickly my entire structure will go up in flames rather than what my insulation looks like afterwards. Here's a neat video showing a real-world comparison of how a fire reacts with fiberglass bat and blown in cellulose (and without any insulation). This is what sold me on cellulose. Click the link to youtube:

The method used to measure R-value is established by the government and, much like the lit cigarette smolder test, the established measurement system really only measures part of the picture. We also know that Washington is full of lobbies that can probably affect how these measurement systems are updated/changed/modernized. Again, like is the case with measuring fire retardation, I don't believe the current method of establishing R-value really takes into account how the entire insulation system works together with regards to how the insulation is installed, how it reacts with in-wall structures and obstacles, or how likely it is to be installed in a different manner from it's testing, etc. I also believe cellulose has a huge advantage in this area that is not properly reflected in the number assigned by R-value. It is much easier to install and completely fill around in-wall obstructions, the corn starch in it makes it firm up and is not only non-toxic, but prevents it from settling, and it provides much better air flow resistance both through the wall and inside the insulation fill.

So, in short...I am really happy with my choice to put cellulose in my building. I can't say that it is helping provide me with smaller utility bills since I don't have an apples to apples comparison with fiberglass, but I can say that everyone that has worked in the building before I had the HVAC running was astonished at how stable the room temperature is throughout the day and night (noticeably cooler 2nd floor - 80 degrees inside on a 98 degree day with no HVAC). I also have only seen a slight bump in my utility bill since I started heating/cooling the upstairs full time.

 

[Steevo]

I am very happy with the insulating value and sound deadening qualities of the 18" of blown-in cellulose insulation I put in my shop attic.
It is very low cost to heat during the winter and doesn't get hot from above in summer.

I can't speak to the fire performance, as I haven't set my shop on fire.

I think the surveys will always go pretty close to 50/50 on the fiberglass/cellulose question, much like copper vs. black pipe, Ford vs. Chevy, sheet rock vs. OSB, 4-post vs. 2-post, etc. etc.

 

[bullnerd]

Steevo,I've seen some pics of your shop,I will be doing something similar.What did you use for a ceiling and did you use a vapor barrier?