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Old 05-16-2007, 07:28 AM   #1
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Attic Insulation, Blown-in or Batts


I'm wanting to add additional insulation to my attic where the current insulation is the blown-in type. Does anyone know whether it's acceptable to lay unfaced batts over top the blown-in stuff or should I just blow more in on top? The current blown-in insulation just covers the top of the rafters now.

Any opinions welcome.

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Old 05-16-2007, 07:53 AM   #2
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Attic Insulation, Blown-in or Batts


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Originally Posted by Tony Papa View Post
I'm wanting to add additional insulation to my attic where the current insulation is the blown-in type. Does anyone know whether it's acceptable to lay unfaced batts over top the blown-in stuff or should I just blow more in on top? The current blown-in insulation just covers the top of the rafters now.
Any opinions welcome.
TonyP
Is there are particular reason why you want to add more insulation? Do you know for a fact that the current insulation is inadequate?

FWIW - You could contact an insulation company, or companies, and get quotes. They can come out and determine the R-value currently in your attic, and then give you an estimate for doing the 'blown-in' insulation. I say this especially because of the fact that it is less expensive to do blown-in fiberglass, over doing the batts insulation. Last job we did, the Blown in was significantly less in cost.

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Old 05-16-2007, 12:07 PM   #3
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Attic Insulation, Blown-in or Batts


In my area it is actually cheaper to have a pro insulate for you. They get the stuff so cheap you end up spending more for the materials than the cost of having someone do it for you. I would definitely get a few quotes.
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Old 05-16-2007, 06:31 PM   #4
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Attic Insulation, Blown-in or Batts


I think blown in insulation, especially a service you pay for is not worth the money. Unless you know what density equals what R rating I would lay fiberglass blankets perpendicular to the joists.
The attics I've seen do not achieve the paid for r rating.
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Old 05-16-2007, 06:47 PM   #5
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Attic Insulation, Blown-in or Batts


Like AC says I would measure and verify what you have now to determine if you need more.

I just over layed my blown in with unfaced and it is a little work, but worth it if you truely need the additional.

Watch the big box stores in the fall for rebates. I saved 225.00 working the rebates.
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Old 05-18-2007, 01:42 PM   #6
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Attic Insulation, Blown-in or Batts


You only pay once for insulation, PERIOD! We do blown in cellulose as a sideline, and I challenge anyone to show independant research that fiberglass, faced or unfaced, beats cellulose. The myth of fiberglass is that air can "travel" through...you don't believe this, try it.....cellulose, as it "settles", actually becomes tighter, and the R value is the same or increases slightly.

[quote]
I think blown in insulation, especially a service you pay for is not worth the money. Unless you know what density equals what R rating I would lay fiberglass blankets perpendicular to the joists.
The attics I've seen do not achieve the paid for r rating.
Ron[quote]

In Oklahoma, we add an average of 8 inches in existing homes, to get to an R40 value...new construction gets 12 inches, and the walls are also blown, which meets the energy codes of 4 inch walls, which is nearly impossible to do with batted fiberglass.

You may not need more insulation, but at a cost of .60 a sq/ft installed, on average around the country, it will pay back benifits over the long run. Energy isn't cheap, and saving where you can counts. Another added benifit of cellulose is the checkical treatment (borate) is a fire retardant, and mice and insects cannot tolerate it.
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Old 05-19-2007, 07:35 AM   #7
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The blown in insulation requires chemical retardents to be fire resistant while the fiberglass is inherently fire resistant, which make bats more attractive to me. But I could be wrong, I'm here to learn.
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Old 05-19-2007, 08:44 AM   #8
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You can buy large tubes of cellulose insulation at Lowe's and if you get at least 8 tubes, Lowe's will let you borrow their blowing machine for free. Each tube is about $8.

In my opinion, blown insulation provides better coverage, but does not keep as lofty as batt insulation. The cellulose must be treated to keep from absorbing moisture and to be fire resistant, but I would double check that. About 6 inches should be enough.
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Old 05-19-2007, 10:08 AM   #9
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Attic Insulation, Blown-in or Batts


Try www.NAIMA.org

Type "comparison" in the site search box.

There are some good resources on blown in versus batts, weight factors, and suggested R levels.

Fact Sheet #35 is very instersting as an overall comparison.
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Old 05-19-2007, 12:54 PM   #10
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Attic Insulation, Blown-in or Batts


Sammy -

Did you happen to notice it was not an unbiased impartial comparison?

From what I saw, that group represents fiberglass and rock wool manufacturers and not other types of insulation. - They do a good job of making it look impartial and fair. - In short it is just another promotional group with slanted facts.

They never mentioned that fiberglass does hold moisture and the 1/2 to 1% moisture can cut the insulation "value" in half.

Also, I never did see where they admit that a R19 in a steel stud structure may give you only a R11 or R12 wall. You cannot get a R19 wall with R19 insulation.
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Old 05-19-2007, 01:48 PM   #11
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Attic Insulation, Blown-in or Batts


CM,

I just suggested it as a possible authoritative source since they are a national association of mfg's of the stuff. I would ASSUME all of the mfg's could join if they wanted to.

But then again I used to live in Washington, DC and there are associations for the association of associations. And as we all know they can skew some numbers to make it look like lettuce is a good insulator.
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Old 05-19-2007, 11:08 PM   #12
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Attic Insulation, Blown-in or Batts


I've seen demonstrations first hand (with a heat source and thermometers showing that cellulose is a better insulator than fiberglass. That being said, if its a small attic, it might be easier to just get some batts and put them down verses setting up the maching and running hoses etc. A big advantage to blown in though, is that where you have areas of your attic that would be hard to get into (where roof slopes down near the attic floor at the eaves), it is much easier to place yourself in a central location and just point the hose out to the eaves and other areas and let the maching do the work of blowing the stuff out there. Saves alot of trouble in climbing around and physically placing the individual batts.
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Old 05-20-2007, 09:19 AM   #13
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Attic Insulation, Blown-in or Batts


Also, I think blown cellulose is a great way to recycle, if you're into preserving the environment.
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Old 05-21-2007, 07:19 AM   #14
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Attic Insulation, Blown-in or Batts


I'm not a tree hugger...but I am a fan or recycling stuff to the point of being practical. That said, I like cellulose, I can't speak for all brands but the Cacoon brand achieves a class 1 fire rating...and if you have a lot a creepy crawlers in your neighborhood, there's a version that is treated to make the attic less inviting to the critters, but I "think" it has to installed by a pro.

I personally think ceiling insulation is the best place to start when looking at decreasing one's energy usage. The house I'm building now, has 16" and is located in central Iowa and recommended for a ceiling R49, I should have around an R56+-. It gets darn cold, and I'm not fond of heating the great outdoors, and we KNOW energy prices will go up in the future.

If you want to read up on researched based un-biased insulation information you might want to spend some time at the Oak Ridge National Labratory web site.

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