# fiberglass batts vs. cellulose insulation



## rmcfall (Oct 28, 2007)

Does any body know which has a higher R value when placed inside exterior walls?  Blown-in cellulose, or fiberglass batts?

The reason I am asking is because I recently realized that not ALL of my exterior walls are block and brick.  Most of them area, but there are a couple that are made up of stud walls.  Actually, those with stud walls are in areas of the house where siding was used instead of brick.  To insulate the majority of my walls, however, I will have to build new stud walls because most of my walls are solid masonry.  I am just debating whether I should blow in insulation in those fews walls where I can, or whether I should remove the plaster and insert fiberglass bats and hang drywall over top (since I will have to hang new drywall just about everywhere else anyway).


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## TMonter (Oct 29, 2007)

I wouldn't put the cellulose in outside walls because of mildew problems I experienced once. Maybe the new stuff is better but I prefer fiberglass and there are also some other options now.


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## KeithO (Oct 29, 2007)

Just consider that cellulose is the stuff that rodents dream of making their nests out of.   Not quite the same thing with fiberglass, but at the same time it will not block their passage.  The fiberglass is certainly an irritant, so if you get any "friends" they will not be "happy friends" the way they would be if you had cellulose in there.

Another point is fire safety.  Cellulose is treated with a fire retardent, but that doesn't change the fact that it is paper based.    Fiberglass may have a coating (very very thin) that may be combustible, but I would say there is several orders of magnitude difference between the 2 materials on combustion, which would favor fiberglass every time.   And finally, fiberglass is pretty durable.  paper based material is really biodegradeable even though I bet it is treated with some sort of preservative to delay this effect.    I personally have not heard of too many health friendly flame retardents and preservatives and consequently I would rather have neither.    There are enough people running around with cancer for me to re-consider my priorities.


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## jklingel (Oct 29, 2007)

I would not put cellulose in a wall, as it settles, leaving you with a crack in your insulation. I blew it over the 'glass in my lid in 1980, and it seems to have made a nice blanket, maybe 6" deep. I may "update" it some day, too; hard to have too much insulation, IMO.


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## Hogwildz (Oct 29, 2007)

Blown in good is great for attics, sucks for walls. As previously stated, it settles, and there goes you r value to the floor.


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## thephotohound (Oct 29, 2007)

The R-value difference between fiberglass batts and blown-in cellulose is negligible. I agree with the rest of the posts... fiberglass in walls.


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## Nofossil (Oct 29, 2007)

One other consideration - if fiberglass gets wet, it's fine as soon as it dries out again, and it dries pretty easily. Not so for cellulose.


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## eba1225 (Oct 29, 2007)

I have looked into fiberglass and cellulose and came up with alot of the same issues that are lised here.  Cellulose settles and in doing so looses some of it insulation value, fiberglass does not settle nearly as much.


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## rmcfall (Oct 29, 2007)

Thanks for all the response...they make my decision easy.


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## gssteve (Nov 13, 2007)

FACT:  fiberglass batts and/or loose-fill blown fiberglass loses R-value as temps vary from 75 F, significantly below freezing, as much as 50% down to -18 F.  Proven by Oak Ridge National Lab and Brookhaven National Lab.  Due to convective air current problem due to high air infiltration design.  Cellulose R-value stays constant.
FACT:  fiberglass has difficulty dissipating excess condensation and does not have mold-fungii retardant.  Cellulose manages moisture by wicking moisture to its exterior surface allowing surrounding air movement to pull moisture out.  Cellulose actually does not require a vapor barrier.
FACT:  fiberglass has definite health issues.  Cellulose is considered nothing more than a nuisance dust by EPA.
FACT:  fiberglass does not burn....IT MELTS.  Cannot provide a barrier against flame spread in the event of a fire.  99% of the homes burnt recently in CA had fiberglass in the walls and most in the attics.  TO THE GROUND!  I've seen homes side by side, one with f/g and other with cellulose.  Trust me anyone would appreciate the end results of the home insulated with cellulose.  Fiberglass is toxic when burning.  Cellulose is not.  BREATH THAT!
FACT:  the issue of settling is acceptable in an attic area.  If settling occurs in a wall it was not blown correctly.  The required wt. of cellulose in a wall is over 2 times that of an attic blow.  With the proper amount you will not have settling.  If you don't prime before painting the paint doesn't last near as long.  Do it Right!
FACT:  With a monolithic seal of cellulose insulation surrounding the living area of a home, the # of air turns will be reduced from 20% to 40%.  An airturn is when conditioned air escapes a home and is replaced with unconditioned air from the outside, thus the thermostat kicks your furnace on.  Anyone for saving utility costs. 
FACT:  on a hot summer's day measure the temp of f/g in your attic and compare temp with attic filled with cellulose.  Where do you think the heat that lingers at the ceiling of a f/g home comes from.   A cellulose home will keep the ac from kicking on as often.
FACT:  the chemicals used in cellulose do not seperate from the cellulose pulp fibers.  They remain permanently together.....we're talking last 20 yr. technology folks.
The US fiberglass companies have a real niche for using their own drummed up propoganda as well as lobbying Washington to stay out front as the #1 insulation supplier.  Other countries heavily concerned about energy consumption (China, Canada, New Zealand, Australia, Russia) cellulose is in great demand.  Go figure!


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## gssteve (Nov 13, 2007)

rmcfall said:
			
		

> Does any body know which has a higher R value when placed inside exterior walls?  Blown-in cellulose, or fiberglass batts?
> 
> The reason I am asking is because I recently realized that not ALL of my exterior walls are block and brick.  Most of them area, but there are a couple that are made up of stud walls.  Actually, those with stud walls are in areas of the house where siding was used instead of brick.  To insulate the majority of my walls, however, I will have to build new stud walls because most of my walls are solid masonry.  I am just debating whether I should blow in insulation in those fews walls where I can, or whether I should remove the plaster and insert fiberglass bats and hang drywall over top (since I will have to hang new drywall just about everywhere else anyway).



Its not so much about whose is the highest.  The advertised R-value of fiberglass is not necessarily the working R-value of same.  All insulation types are tested at 75 F.  When temps vary from that f/g's R-value is subject to reduction, as much as 50% at a - 18 F.  Oak Ridge National Lab and Brookhaven National Lab did studies on this.  The variance is caused by a sceintific term called "convective air current".  Air flow thru the glass fibers are effected by the temp of the air.  Cellulose is 3.8 R-value per inch and will stay constant at all temps.


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## gssteve (Nov 13, 2007)

TMonter said:
			
		

> I wouldn't put the cellulose in outside walls because of mildew problems I experienced once. Maybe the new stuff is better but I prefer fiberglass and there are also some other options now.



If you had mildew problems in your walls, either you had water intrusion from a defectively designed wall assembly or you had someone blow it in a newly constructed home and they used too much water and no aeration before buttoning up the wall.  Brick sided home, if not properly vented behind brick, will transfer moisture into the wall assembly which can reach the insulation.


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## gssteve (Nov 13, 2007)

KeithO said:
			
		

> Just consider that cellulose is the stuff that rodents dream of making their nests out of.   Not quite the same thing with fiberglass, but at the same time it will not block their passage.  The fiberglass is certainly an irritant, so if you get any "friends" they will not be "happy friends" the way they would be if you had cellulose in there.
> 
> Another point is fire safety.  Cellulose is treated with a fire retardent, but that doesn't change the fact that it is paper based.    Fiberglass may have a coating (very very thin) that may be combustible, but I would say there is several orders of magnitude difference between the 2 materials on combustion, which would favor fiberglass every time.   And finally, fiberglass is pretty durable.  paper based material is really biodegradeable even though I bet it is treated with some sort of preservative to delay this effect.    I personally have not heard of too many health friendly flame retardents and preservatives and consequently I would rather have neither.    There are enough people running around with cancer for me to re-consider my priorities.



Place a section of batt insulation on a surface and place a 2x4 on top.  Create a mound of fluffed cellulose on a surface and place a 2x4 on top.  Apply a portable blow torch flame to either and watch.  You'll change your mind about cellulose.  Fiberglass is not durable in the event of a fire.  It doesn't burn, it melts and rather quickly.  It will certainly reduce the amount of time you would need to get your family out of the burning structure, including Fido.  Cellulose is treated with harmless commonly used chemicals found in lots of home products.  No preservatives are used.  Cellulose is not designed for pest control exclusively.


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## gssteve (Nov 13, 2007)

jklingel said:
			
		

> I would not put cellulose in a wall, as it settles, leaving you with a crack in your insulation. I blew it over the 'glass in my lid in 1980, and it seems to have made a nice blanket, maybe 6" deep. I may "update" it some day, too; hard to have too much insulation, IMO.



Cellulose must be blown in a wall cavity at approximately 3.0 lbs. per cu.ft. minimum to eliminate settling.  It's like anything else, if you don't do it right it wont end up right!  There are thousands of professional installers around the US that are blowing it correctly and the homeowners are living comfortably and saving on utility costs.


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## gssteve (Nov 13, 2007)

Hogwildz said:
			
		

> Blown in good is great for attics, sucks for walls. As previously stated, it settles, and there goes you r value to the floor.



Like anything else, if you don't do it right it won't end up right.  Takes 3 lbs. of cellulose per cu.ft. of wall area the keep from settling, about twice what it takes in an attic, although settling is an accepted characteristic in an attic.  If you had settling it wasn't blown correctly, simple as that.  If hiring it done you should get references on an installation contractor, though most don't.


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## gssteve (Nov 13, 2007)

ThePhotoHound said:
			
		

> The R-value difference between fiberglass batts and blown-in cellulose is negligible. I agree with the rest of the posts... fiberglass in walls.



You evaluate any thermal insulation on the basis of performance, health and safety.  Fiberglass loses R-value as temps vary away from 75 F,  has known health issues and has a low melting point in the event of a fire allowing rapid flame spread.  Cellulose's R-value stays constant,  has 0 health issues and does not burn putting up a barrier against flame spread.  Oh yeah, you'll save a nice chunk of bread over the life of the home due to its reduction of air infiltration saving energy.  Go fiberglass, you're kidding!


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## gssteve (Nov 13, 2007)

nofossil said:
			
		

> One other consideration - if fiberglass gets wet, it's fine as soon as it dries out again, and it dries pretty easily. Not so for cellulose.



Cellulose has a wicking action characteristic when it comes to managing moisture.  Place a paper towel over a puddle of water.  Watch it spread out, then leave it to set.  Come back to it a couple hrs. later and the paper towel has dried.  That's because it continuously wicked the moisture to the exterior surface of the towel allowing the surrounding air movement to pull out the water.  That's what cellulose does continuously.  Of course, if its fluent moisture your insulation and your home has got structural problems.  With fiberglass the moisture beads up on the strands and has to rely on the movement of air thru its interior.  Some of that air is what you paid for to have conditioned by your furnace or ac.  That's consuming more energy to condition the air in your home due to f/g's high air infiltration.  I'm not rich, how bout you?


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## TMonter (Nov 13, 2007)

Celluose is also treated with Borate who's health effects are questionable. As with all insulations proper installation is a must. If you're looking for the best insulating value, adding a minimum 1" of rigid foam on the exterior studs is by far the best value.


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