# What type of insulation is best?



## BlueBSH (Oct 29, 2009)

I had an energy auditor come out and they where pushing cellulose blown fiber like crazy. Right now our attic has blown fiberglass, but its lacking, its barely covering the 2X6 joists in the attic. I was going to get more fiber blown over top to take it up to R-40 but they said to go cellulose instead overtop of the fiberglass. their reasoning was it will slow down air movement more then fiberglass.

I've been reading a lot like that online, but then also reading a lot saying don't do it because its "guaranteed to harbor mold being an organic substance"... :huh:

what should I do?! What is better, what is more cost efficient? Noise infiltration is also a concern, the attic space in this area acts like a resonance chamber, all the road noise is amplfied a good bit then the master bedroom right below gets all the noise..


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## svaic00 (Jul 2, 2012)

Blue,

Got a questions for you, could not find anyway to contact you other than to reply to a post, I would email you but could not find a link to send you any kind of message. Back in October 2009, you posted a thread asking 

"Is there a "Best" glue pattern to attach XPS to concrete walls? Or is a few vertical lines of it with the top and bottom also glued horizontally alright? Can't find much information on this online.."

In the thread someone responded to you about using liquid nails, or any PL product. Your final response was "The PL adheasive I got is tan and it says "any foamboard product" on the list of applications" I was just wondering what adhesive you used, did it work well, did you need to temporarily support the boards while the adhesive set?

Thanks,
Steve


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## svaic00 (Jul 2, 2012)

Not sure what is best as far as cellulose vs fiberglass. But our attic has 2x10 joists, along with a truss roof system. We have blown fiberglass over the flat ceilings that is approx 18" deep, and we have no problems with any noise amplifications. We also dont really ever feel any airmovement or cold/hot air from the attic, because the insulation is so thick. In the areas where we have a sloped ceiling in our master, they used 10" thick fiberglass mats, and then blew extra insulation on top of that.


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## BlueBSH (Oct 29, 2009)

svaic00 said:


> Blue,
> 
> Got a questions for you, could not find anyway to contact you other than to reply to a post, I would email you but could not find a link to send you any kind of message. Back in October 2009, you posted a thread asking
> 
> ...


lets try not to go too off topic here, but I used PL Liquid nails.. just look on the back of the tubes, it will list what it works with, it should say foamboard and concrete... the contact isn't an instand hold, you have to put braces up against it until it sets in about an hour to a tack that is strong enough... I just sat 2x4's at an angle against it... used about 6 per sheet of XPS put up... glued one sheet, braced it, glued the next braced it waited, moved down the line until it was done moving the braces as it set to a strong enough tack...


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## Windows on Wash (Aug 30, 2011)

GBR has several threads on here about the cellulose vs. Fiberglass comparison.

Cellulose wins on all accounts.

Mold needs moisture to grow and will grow on fiberglass as well. If you have a bulk moisture issue that is keeping the insulation wet, that is another issue altogether that needs repair.


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## BlueBSH (Oct 29, 2009)

Windows on Wash said:


> GBR has several threads on here about the cellulose vs. Fiberglass comparison.
> 
> Cellulose wins on all accounts.
> 
> Mold needs moisture to grow and will grow on fiberglass as well. If you have a bulk moisture issue that is keeping the insulation wet, that is another issue altogether that needs repair.


yeah, there is no moisture issue, but when you read a bad story on it, you think about it twice... what about cellulose they blow into wall cavaties when walls are being framed? don't they wet it somehow to get it to stick vertically? I thought I saw something on that before when the house was in pre-drywall stages they blew it in at higher pressures like a gun when it was dampened with something then they "shaved" it level with some kind of device so its the same height as the studs.. if you do that, does it need a drying period before you can drywall?


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## jklingel (Dec 21, 2008)

cellulose that is treated w/ BORATES will not harbor mold any more than any other insulation that has liquid water in it. in fact, such cellulose will absorb some water vapor in winter, then dry in the summer w/ no issues. that is one of the beauties of it. borates inhibit mold growth and discourage critters from nesting there, etc. cellulose WILL crust over a tad and prevent air flow; fiberglass that is not dense packed into a wall will stop air like a window SCREEN. bad application for fg. be careful reading anecdotes about anything when you don't have "the rest of the story". wet blown cellulose needs a few weeks or so to dry, and naturally it needs to be installed properly like anything else.


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## Perry525 (Jan 10, 2010)

The best insulation is closed cell polystyrene.
Polystyrene is wind proof and waterproof.
It was brought to market 51 years ago by Dow under the name of Styrofoam, polystyrene installed then is still working today and is still as good as new.
Polystyrene is easy to work, it can be cut to size with a knife or hand saw, professionals use a hot wire which is easy and clean.
Polystyrene sheet can be cut and fitted between the frame and fitted over the frame on the inside or outside to save on heat loss or gain through the frame by conduction.


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## ryanxo (Jun 7, 2011)

Blue there are basically 3 kinds of easily available insulation for an attic.
Fiberglass, Cellulose, and spray foam.

Fiberglass in my opinion and apparently many others opinion sucks. Mold likes it, air can seap through it and mice don't mind it either. If you get the batts then make sure there are no spaces between it because air can just blow through.

Cellulose is fiberglasses big rival and it has less air movement, more fire resistance, rodents don't like it as much and it has things added in to fight mold.

Spray foam is the next big thing going in most new construction. It is more expensive and is recommended to be done by a pro but it is an air sealer, deadens noise by ALOT and the closed cell stuff is R-7 per inch which is double fiberglass and cellulose. Most of the time though spray foam is used on the underside of the roof to close off an attic into an "unvented" attic and turns it into a conditioned space. Aka it wont get more than 85-90 degrees which is pretty awesome if you store stuff up there.

Best part about cellulose is... IT DOESN'T ITCH...which i guess is only a concern if you do work in your attic


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## jklingel (Dec 21, 2008)

Spray foam is good stuff, but expensive and we need to remember that it is not the best insulation for the environment. It has its applications, for sure, but it ain't perfect, either. FG is a last resort material, which I wish I knew in 1980 when we put 13" in my walls. It is OK, but not the best stuff available now.


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## Perry525 (Jan 10, 2010)

*Spray Foam*

Take a look on the net, you will find there are plenty of problems with spray foam.
If the installer doesn't get it right, the foam can crack, fall off.


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## jklingel (Dec 21, 2008)

Perry525 said:


> If the installer doesn't get it right, the foam can crack, fall off.


 Yep. A bad job on critical material is a liability.


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