# Topping up Attic Insulation:  Blown Fiberglass or Cellulose?



## velvetfoot (Nov 16, 2009)

I've got fiberglass batts now.
I have a pre-disposition against blowing cellulose on top but so far haven't found a contractor that does fiberglass (just started calling though).

Anybody out there that could give me some guidence?
A contractor recommendation for Albany, NY area would also be awesome.

Thanks.


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## NEDLAX (Nov 16, 2009)

Cellulose will preform better in attic. It will settle so blow more than what you desire for depth.  we blow both but im in Syracuse I dont know anyone out there.  I have found if you go up and feel in the insulation you will feel the heat in the blown fiberglass much higher than the cellulose almost near sheetrock.  Also when it dips under 10 degrees the r-value of fiberglass drops significantly more than cellulose does. Walls are a totally different subject though.


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## Highbeam (Nov 16, 2009)

I had blown in fiberglass placed above the old R-9 batts in my attic about a year and a half ago. The nicer blown in FG doesn't itch and is much less dusty than I remember the cellulose being. It's white too. I chose FG because cellulose is food for lots of animals, food for fire, and seems like somebody's grand idea to recycle more than an innovation. It is also heavier and settles more than FG. My old sheetrock doesn't need more weight on it. FG and cellulose are the same R value per inch so no benefit there. 

I couldn't see any reason to use cellulose but plenty reasons not to. 

I spent lots of time before the blow in going around and sealing all penetrations and installing baffles along the eaves to prevent blocking the ventilation. The old FG batts are super itchy. Your old FG batts include the Vapor barrier so the only benefit I've heard of for cellulose, better air sealing, doesn't matter.

Be sure to take the time and seal the air gaps around likght boxes, wire penetrations, plumbing penetrations etc. Also, after the blowing, go up there and be sure that they didn't fill your insulation guard around the chimney with insulation. Even though it won't burn like cellullose, you want that clearance to combustibles.


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## 00Buck (Nov 16, 2009)

A local fire in a house started from blow in cellulose insulation. But it was also next to the flue. 

http://www.ksl.com/index.php?nid=148&sid=8683892


Fire raises concerns over home insulation
November 15th, 2009 @ 9:45pm
By Nicole Gonzales

LAYTON -- A house fire in Layton displaced a family and caused thousands of dollars in damage Saturday.

Fire investigators said it started near the chimney flue in the attic. They said the insulation was too close to the hot pipe and caught fire -- a problem that could become more common as the winter sets in.

The house, located near 1500 North and Cherry Lane, was declared unlivable. The cost of the damage to the home was estimated at $85,000.

"The past two days we've had two fires -- chimney fire-related -- so this is a concern to us right now," said Doug Bitton with the Layton City Fire Department.

The concern was the fire's origin.

"This vent pipe has a lot of white impingement marks right here," Bitton said.

Bitton investigated for Layton City Fire and said the white marks show where the insulation ignited.

The homeowner had cellulose insulation blown in this spring, thinking it would save energy and money. Just the opposite happened, however.

The family lit their wood burning stove around 4 p.m. Saturday. By 8:00, they knew something was wrong.

"First the electrical went off in the family room, which surprised them, and then they saw a different haze -- color of light -- out the rear of their home," said Bitton.

They evacuated just in time for crews to start their work on the attic. The fire spread through the insulation, so they had to remove most of it.

An hour later the fire was out, and the family was forced out as well.

Bitton said all families need to check the clearance between their flues and the insulation. Most building codes recommend 1 to 2 inches of space, depending on the pipe.

The U.S. Department of Energy suggests putting in a clearance dam or a protective sleeve.

"We don't want any radiant heat hitting this type of cellulose insulation that could cause a possible combustion," said Bitton.

Bitton said local code officials can help people make the right adjustments.


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## szmaine (Nov 16, 2009)

Food for thought...

Cellulose has been given a bad rap and had improved greatly through the years: it's treated w/ borates that make it very fire retardant as well as a deterrent the mice, vermin and mold. Any insulating material if installed improperly can cause fire (ie around old light fixtures etc). If the chimney runs through the attic then you need to build up a dam of fiberglass batts around it. 

One problem that loose FG has that cellulose doesn't is air washing that can dramatically reduce r-value: As the temperature difference between the living space and attic increases, the R-value of blown fiberglass diminishes. In extreme situations, such as the upper Midwest, this reduction in R-value approaches 50 percent.
This phenomena seems to occur as a result of thermal convection. The trapped air molecules in the insulation are pulled up through the insulation into the colder attic air. This problem is apparently solved by installing fiberglass batt insulation over the top of loose fill or blown insulation.


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## Shari (Nov 16, 2009)

Highbeam said:
			
		

> Also, after the blowing, go up there and be sure that they didn't fill your insulation guard around the chimney with insulation. Even though it won't burn like cellullose, you want that clearance to combustibles.



HB, 

Could you explain what you mean by "insulation guard"?

Shari


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## matt701 (Nov 17, 2009)

I know for my double wall stainless chimney, the chimney guard is just a piece of metal that goes over the outside of the pipe making a 2" air gap between the pipe and the insulation and you can then pack your insulation around the guard safely.  A few months ago, I was unbiased and read and read the benefits of both cellulose and fiberglass and went with cellulose as the hands down winner.  I read contractor forums, safety information, reviews and specs for both because it''s a big investment and I wanted to use the best product.  Just do a lot of research and pick what you think is right for you.   I love the youtube video of the guy "proving' that cellulose burns by taking a blowtorch to it for several seconds.


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## closer9 (Nov 17, 2009)

I've got cellulose in the entire house (interior and exterior walls and attic).  The guys that did the walls did a great job, however the guy that came back to do my attic was apparently trying to save some time and insulation.  I didn't bother to check behind all the ductwork closely until several months afterwards.  So, a month or so ago I rented the equipment from Lowes and put an additional 17 bags in the attic (and 3 in my garage, but still need more there).  I never even considered fiberglass of any kind.  I use my attic for storage, and the air handler is up there.  So, didn't want FG blowing around, and getting me all itchy...  I have taken a torch to the cellulose just to see, it will burn, but goes out as soon as you pull the torch away.  It is flame retardant, not proof.  I bet a torch on blown FG would do something similar...  I've had no trouble with pests in the attic, and can't say that I've really even seen any insects (now I'll probably be flooded with bugs, and rodents since I said this)...

Just my $.02, but I prefer cellulose...  very easy to do yourself too...  I'll be finishing the ceiling and walls of my garage with it sometime this winter or next spring...  It works GREAT for sound insulation...


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## Highbeam (Nov 17, 2009)

Shari said:
			
		

> Highbeam said:
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It is the metal shield around your chimney that provides the 2" required clearance to combustibles which can be the wood framing or the insulation. The "ceiling support box" on my simpson system extends into the room about 2 inches but runs into the attic about two feet. The support box is the insulation shield. 

Back to chemistry class guys. Things that end in "ose" are sugars. Things about sucrose, lactose, fructose, and ..... cellulose. Hmmm, do you really want to fill your attic with cotton candy? What happens when you pour a pepsi out on the concrete in the summer? Ants eat it, bees eat it, all kinds of bugs that I don't want in my attic. Have you ever started a sugar cube on fire? Just light it. And yes, that sugar feeds all sorts of microorganisms too for mold and who knows what else. What happens when cotton candy gets wet? Just imagine the syrup pouring through your sheetrock. 

I don't trust for a minute, much less bet my life on it, that the proper amounts of some additive were sprinkled into the cotton candy to make it less tasty to bugs, fire, or mold. That is like them saying that they added lubricity back into the new diesel (per fed regulations) to make it equal to the old diesel when we all know that they didn't and now we have to add lubricity additives. 

So I know that the above cellulose trash talk may be on the extreme end but there are no negatives to the FG which is an inert product and not a sugar.


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## szmaine (Nov 17, 2009)

Highbeam said:
			
		

> Back to chemistry class guys. Things that end in "ose" are sugars. Things about sucrose, lactose, fructose, and ..... cellulose. Hmmm, do you really want to fill your attic with cotton candy? What happens when you pour a pepsi out on the concrete in the summer? Ants eat it, bees eat it, all kinds of bugs that I don't want in my attic. Have you ever started a sugar cube on fire? Just light it. And yes, that sugar feeds all sorts of microorganisms too for mold and who knows what else. What happens when cotton candy gets wet? Just imagine the syrup pouring through your sheetrock.
> 
> I don't trust for a minute, much less bet my life on it, that the proper amounts of some additive were sprinkled into the cotton candy to make it less tasty to bugs, fire, or mold. That is like them saying that they added lubricity back into the new diesel (per fed regulations) to make it equal to the old diesel when we all know that they didn't and now we have to add lubricity additives.
> 
> So I know that the above cellulose trash talk may be on the extreme end but there are no negatives to the FG which is an inert product and not a sugar.



Better watch out, your house is framed with peppermint sticks.

You think you got it bad - my knitting needles are made with cheese. 
http://www.fibersden.com/casein-knitting-needles/


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## Highbeam (Nov 17, 2009)

I know, LOL,  but there is no easy alternative there and the wood isn't prechewed. You can bet I would love to have a house built with ICFs and steel trusses. There are some really cool ideas out there and in other countries that aren't obsessed with wood construction.


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## velvetfoot (Nov 17, 2009)

So far I have a quote over the phone for 1000 ft2 R30/$1600 and R40/$2350 blown cellulose.
FG batts at HD are R38: $.92/ft2, but then they require installation.


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## velvetfoot (Nov 17, 2009)

I just got another quote over the phone.  1000 ft2, $835 for fiberglass and $900 for cellulose.
I think we have a winner.
How can you beat cheaper than doing it yourself?


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## szmaine (Nov 17, 2009)

> I just got another quote over the phone.  1000 ft2, $835 for fiberglass and $900 for cellulose.
> I think we have a winner.




Which are you doing? House of glass or gingerbread?


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## velvetfoot (Nov 17, 2009)

I'm leaning towards glass.


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## szmaine (Nov 18, 2009)

Oddly enough, last night on the local news there was a piece about a house that burnt down in my home town yesterday.
They didn't say the cause of the fire but they interviewed a fireman who made some vague comments about  it being filled with cellulose, and having to "dig through it" for a long time". He didn't really say exactly what he meant - but I got the impression that it was a smoldering issue - which of course could re-ignite, I suppose.


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## peakbagger (Nov 18, 2009)

Back during the first energy crunch there was lots of federal money to insulate public buildings (sound familiar?). There was not a lot of money to fix roof leaks or install vapor barriers. The net result was more than a few buildings with collapsed interior ceilings when the blown in cellulose absorbed moisture from leaks or humidity. Granted fiberglass can absorb some water but nothing like Cellulose.


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## ohio woodburner (Nov 18, 2009)

I've always heard you should alternate types of insulation.  If you have batts then go with blown in then go with batts again if you add more and vice versa.  Just my .01 worth


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## Highbeam (Nov 18, 2009)

I don't know about that. I think you can blow in on top of blown in all day long. Trying to lay batts over blown-in would be difficult to do well. There will always be dips and rises with the blown-in and your batts are supposed to lay against something with no air gaps. The batts are no fun at all in the attic, ever. Blown in is just so easy and such a better product that I would rather blow in cellulose than lay FG batts.


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## velvetfoot (Nov 19, 2009)

I think it's hard to find impartial information on insulation.


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## Highbeam (Nov 19, 2009)

velvetfoot said:
			
		

> I think it's hard to find impartial information on insulation.



I found the same thing. I used blown in FG so I might be biased towards that since it's been great. At the end of the day, lots of people use both cellulose and fiberglass and most don't even know which they have. Since you asked for our opinions though.... 

Rolling out batts, that totally sucks. There's nothing fun about it and even if you hire it out you can be sure that they didn't lay it down as consistently as if it was blown in. They will leave gaps and cracks, or you will leave gaps and cracks. You just can't do it perfectly.


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## NEDLAX (Nov 19, 2009)

Fiberglass is safer in the case of a fire yes, but if your house is on fire and its in the attic is there anything to save? lets focus on not letting a fire happen.  Cellulose preforms better in the attic than fiberglass.... talk to any energy star or building performance institute (bpi) inspector.  I have also seen what cellulose turns into when its twenty years old....powder.  I do both applications personally. In my house i have an R60 bottom half blown fiberglass top half cellulose.  The main thing is get airsealing done its more important than adding more insulation. Look for contractor that usually does new construction they will have a better price than an insulator that does retrofit work.  They shouldnt be that busy not a lot of building happening. my company would blow r30 for $ .60sqft depending on your attic size, room, baffle installed or not.  Good luck


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## velvetfoot (Nov 19, 2009)

I had an estimator come by tonight.  
$1850 for R38 cellulose for 1000 ft2.

The lower price one I mentioned earlier is coming by tomorrow AM.
I'm hoping that works out.
I think the others are high.


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## Hakusan (Nov 19, 2009)

I suppose it would be rather pointless to warn members of this forum not to play with fire...


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## szmaine (Nov 19, 2009)

NEDLAX said:
			
		

> Fiberglass is safer in the case of a fire yes, but if your house is on fire and its in the attic is there anything to save? lets focus on not letting a fire happen.  Cellulose preforms better in the attic than fiberglass.... talk to any energy star or building performance institute (bpi) inspector.  I have also seen what cellulose turns into when its twenty years old....powder.  I do both applications personally. In my house i have an R60 bottom half blown fiberglass top half cellulose.  The main thing is get airsealing done its more important than adding more insulation. Look for contractor that usually does new construction they will have a better price than an insulator that does retrofit work.  They shouldnt be that busy not a lot of building happening. my company would blow r30 for $ .60sqft depending on your attic size, room, baffle installed or not.  Good luck



Since you're in the business...do you know what ever happened to rock wool?
My old house was at some point in the distant past blown full of it but I never hear of it now.


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## velvetfoot (Nov 19, 2009)

I'll add that a co-worker, who's selling his house, told me his 9 year old prefabbed house that was shipped in sections from PA, has 12" of loose fill rock wool in it.

I know you can buy batts in Canada-not sure about blown.


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## allhandsworking (Nov 19, 2009)

Highbeam said:
			
		

> I had blown in fiberglass placed above the old R-9 batts in my attic about a year and a half ago. The nicer blown in FG doesn't itch and is much less dusty than I remember the cellulose being. It's white too. I chose FG because cellulose is food for lots of animals, food for fire, and seems like somebody's grand idea to recycle more than an innovation. It is also heavier and settles more than FG. My old sheetrock doesn't need more weight on it. FG and cellulose are the same R value per inch so no benefit there.
> 
> I couldn't see any reason to use cellulose but plenty reasons not to.
> 
> ...



Cellulose is treated with boric acid!  No bugs!  Treated with fire resistant cemicals.  Aim blow torch at hand with 2" of cellulose No burn!


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## allhandsworking (Nov 19, 2009)

I may be wrong but from my experience as a NYC Fire Fighter I have done lots of overhauling inside burned homes and buildings. Fiber glass inside bays are usually burned up or melted! Cellulose is usually intact. Wood studs are usually not alligatored or charred! So it seems like a good fire-stop! I am not an expert on the material or the instillation.


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## velvetfoot (Nov 19, 2009)

The estimator for the last company just left.
$850/R38/1000 ft2/Blown fiberglass to Owens-Corning's specs.  December timeframe.
The proof is always in the pudding, but a grand less!
I'd heard there could be wide variations but that's crazy.


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## Highbeam (Nov 19, 2009)

You'll love it 

My soda pop is treated with phosphoric acid and citric acid, bugs love it.


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## CJRages (Nov 19, 2009)

Lowe's offered a great deal on blown in attic fiberglass insulation in October. The Owens Corning Atticat delivery system is free to rent for one day as long as you purchase the required number of bags of insulation - otherwise $20 for a day. 

The promotion was: spend at least $400 on insulation and receive a $100 Lowe's gift card. I bought just enough to get over $400. The stuff is 30% tax credit eligible also. I'm not sure if they are still offering this, but you should check into it. It was an fairly easy install. I received approx. 1400 square feet of R 20. 

It was an nice process. I was in the attic controlling the spread of the pink fluffy stuff. My friend outside fed into the machine the compressed chunks of fiberglass. This fiberglass did not have the irritating scratchy property of the fiberglass batts. The insulation was softer and very fluffy - like a snow shower when it came out the hose in the attic. Make sure you wear a face mask for breathing up there though. Otherwise a very clean, quick process.

EDIT: I've been looking online - I think the promotion from Lowe's is over. It's still an inexpensive alternative if you have DIY inclinations.


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## velvetfoot (Nov 19, 2009)

I would if I had any friends.


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## btuser (Nov 19, 2009)

I had the blown-in Fiberglass insulation in my attic when I fist moved in.  It was level with the ceiling trusses (6") which only gave me r19!  I rolled out non-faced r30 batts perpendicular to the trusses so the cavities are fill with loose insulation and the batts are on top.  The combo gives a combined r49.  No more ice dams.    900 sqft was around 600 bucks  (installed myself) but don't forget the tax credit for insulation is going to cut your bill in 1/2.

The reason r50 is prefered in attics is because of the degradation of insulation in very cold weather.  Fiberglass is worse, but after close to 20 years of breathing borate-laced cellulouse the taste/smell of it just pisses me off, making me relive memories of bad times in attics as an apprentice.  I DO NOT want that stuff in my house.  When it -20 degrees outside the fiberglass is closer to r30, which has about 95% the capacity of r50.    Celluose is better, I just hate the stuff.


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## imiller1974 (Nov 20, 2009)

My wife and I blew in 50 bags of cellulose last year on Oct. 31 for $340.00. Homedepot had the cellulose for $9.93 a bag. Lowes had it for $8.67 a bag. I had Homedepot price match plus 10%, but the lady running the computer entered the price wrong. She was supposed to enter the Lowes price, and the computer would do the 10% calculation. She did the calculation on her calculator, then entered that price into the computer, so I payed $7.02 a bag, then got an additional 10% by using a Homedepot credit card. She actually caught her mistake, but gave me a wink, and told me to haul ass. The blower rental was free for 24 hours for every 20 bags purchased. It took us about 4 hours taking 3 breaks.

The process isn't too bad for the person in the attic, granted it's not during the summer. We plugged to hose up twice trying to go too fast, but I got the slide valve set right for my wife and she didn't have any more problems. I manned the hose in the attic, and she fed the blower. The attic person has it made. The person feeding the machine has it rough. 

I also put in R-19 insulation in the floors that month. Between the attic and floor insulation, it dropped our electric bill about $10 a month. I spent a little under $1000 total...


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## blujacket (Nov 20, 2009)

My wife and I topped our 5" cellulose with R-30 fiberglass batt rolls. Lowe's had it for $9.37 a roll with a $100.00 mail in gift card for $400.00 spent. We used 47 rolls, total was $471.22. After the gift card will be $371.22. Big difference so far. Heat pump runs 1-2 times a day.


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## NEDLAX (Nov 21, 2009)

szmaine said:
			
		

> NEDLAX said:
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 They still have it, well batts never seen it blown, sometimes its called thermal fiber. I had to use it yesterday for fireblocking between floors.  I also used it around my pipe to keep insulation away from shield.  Are you sure it was rock wool or vermiculite blown in it?


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## velvetfoot (Dec 3, 2009)

Well, they came and did the job today.  It looks pretty good to me.  They put in some extra vents as well-mine might have been marginally long enough.  Now that I think of it, I'm not sure if they put them up in each bay, but I'd have to mess  with the batt they put on top of the hatch cover (and which of course I messed with after they went to look up there) - anyway I thought that was a nice touch.  I made a little bit of a deal on how many bags they were going to blow in there (Pink Panther says 19.5 bags for 1000 ft2 R38, not in Minnesota, which specifies more).  I stood by and watched and counted 21 bags, but at least 20.  They put up the height markers too and that seemed to check out too (forgot now, but around 14" I think).  Amazing how quick the actual blowing went - the harder part is the "prep", like other things.  I guess it's standard for the pros but the thing is radio controlled, not sure how much info is transferred, but the blower is remotely controlled.  I don't know if the guy in the attic actually knows how many bales he's used or how he knows he's gonna hit the target - it didn't seem anyway that the two guys were talking, but I could be wrong.


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## Highbeam (Dec 3, 2009)

Turns out you don't need those baffles on every joist bay. Just like you don't need the bird blocking on every joist bay. Still, I put them on every one because I'm just like that.


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