# Selecting insulation type when adding batts to attic



## cbaur88 (Jan 25, 2011)

operagost said:


> My attic currently has insulation blown-in to the top of the rafters. I would like to air-seal, then lay batts perpendicular to the rafters. I'm using batts instead of blowing in more insulation because when I do electrical work in the future, it's much easier to pull back a few batts than scoop up blown-in stuff. Plus, it's hard to replace the blown-in stuff evenly. What I've found from my research is:
> Fiberglass batts: need mask and gloves to install due to fibers; allow lots of air to pass through
> Rock wool batts: need mask and gloves to install; slightly higher R value than fiberglass; slightly more expensive than fiberglass
> Cotton batts: Slightly higher R value than fiberglass; hard to cut; more expensive than fiberglass.
> ...


I agree the batts vs. the blown insulation will be more easier to move around for doing home improvement projects. I am beginning to flat out hate fiberglass. It's just so nasty to work with, gets in your throat, on your skin etc... I just picked up some Roxul for my crawl space. I haven't even cut the bag open yet but I am eager to work with it. I hear it's really easy to cut (with a steak knife) and a better insulator then fiberglass without the hassle as well. But it's more costly for sure. Johns Manville has fiber encased in plastic that's easy to work with and touch. Comes in faced or unfaced as well which can be an option for you. For the best insulator spray foam is prob the best but it's $$$$.

What's your plan for air sealing it? Just moving the blown stuff around and sealing? I'll be eventually doing this same project once my crawl space is completed. I have some blown in insulation with batts (facing the wrong way) on top giving me about 7" - 8" of insulation not much R-Value


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## operagost (Jan 8, 2010)

J-M is out of the question because of issues related to their handling of asbestos-- too long to go into. If rock wool products like Roxul are a little more pleasant to work with than fiberglass, that would be fine. It's going to be unfaced, being the top layer. 

I'm going to shift the existing fluff out of the way the best I can. It's just impossible to get it settled back in nicely without blowing it in again. I'll be caulking in the small holes and foaming in any bigger ones (like wiring holes). I think it'll pay back within a short time, because I was able to measure a temperature drop of a few degrees on any interior walls containing wiring compared to those without.


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## Wildie (Jul 23, 2008)

I like Roxul! I insulated my entire attached garage with it. It has excellent fire blocking characteristics.
However, when I hired a fellow to lay insulation over my fibre glass insulated attic, I had him use fibreglass again, as it seemed to me that it might be best not to mix types.
At the end of the day, I doubt that it makes any difference. So, all things being equal, then price could be the deciding factor.


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## cbaur88 (Jan 25, 2011)

Yes I hear you, I use to be an IT Admin for a law firm who handled allot of suites against J-M for asbestos. 

I got down in the crawl last night to do some work and finally go to use the Roxul. I really like the stuff so far. I am amazed at how easy it is to cut, what a piece of cake. I also like how I am able to compress it more then fiberglass. I always felt it was so tedious fitting fiberglass and I was compressing it too much. Anyways I am please with it so far.


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