rock wool insulation in attic replace or add to it?

I have rock wool insulation stapled to the rafters of my cape cod built in 1952. It's in pretty good shape but I'm not sure if it should be replaced or augmented. My 2nd floor is always a degree or two colder than my 1st floor in the winter so I decided I'm in need of some insulation. I checked and noticed that where the dormers were added there is a lack of insulation. A handyman I had doing other work on my house said that the wool insulation is better than the fiberglass and I should keep it and just add some insulation to the knee joints near the dormers where it is lacking and that should be enough. I'd like to take care of this correctly so I'm wondering what the conventional wisdom of rock wool insulation is. Is there an R value for it?
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appears rock wool and fiberglass are same per inch, around 3
closed cell foam is over r6 per inch.
i would pull up the rock wool and replace with closed cll foam
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snipped-for-privacy@aol.com wrote:

Only if it's completely covered with plaster or drywall, right? Because foam burns like crazy and must never be left uncovered. I don't think any codes allow it to be left exposed. If covering the insulation isn't possible or practical, there's dense fiberglass, also rated about R-6 per inch, that's safe to leave uncovered.
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wrote:

Spray in place closed cell foam is superior because it expands and seals all the tiny gaps, holes around electric outlets etc.
Rooms will be noticeably quieter and more comfy.
if your going to all the work to replace the insulation you might as well go with the best!
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http://www.coloradoenergy.org/procorner/stuff/r-values.htm
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Wow, so if I only have 2 inches of Rock Wool insulation in my attic I only have a maximum of R value of R-8? What is the recommended R value for attics? Isn't it around 40?
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snipped-for-privacy@gmail.com wrote: ...

Sounds about right...2" of much of anything other than the new foams isn't much actual insulation value...

Depends on where you're located--in really cold climates, yes; more moderate 30 or so is probably about the point of diminishing returns.
Your local po-co undoubtedly has energy conservation services and can provide recommendations and quite possibly even do energy assessments at no or very low cost...
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If you have the room, just add to it. More is always better.
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I assume that the area under the rafters is heated. If not, the insulation is normally between/above the joists at the top of the ceiling of the heated area.
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Well, it's a cape cod which means that the 2nd floor is basically the attic and the areas I'm talking about are the crawl spaces where there is no head room. They are generally closed off and used as storage space. The places where we have rock wool insulation are parallel to the heated living area and cordoned off by dry wall so there is a need to have the insulation against the roof. I don't have access to the attic so I'll need to cut a hole in the ceiling to see what is up there but I assume that is rock wool as well. There I assume I can do the standard type of insulating right above the ceiling.
I'd hate to take down the rock wool since it doesn't seem to be degraded in any way, my preference is to add insulation over it. Can I just staple fiberglass over it or is spray foam my only real option due to the gravity situation?
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On Jul 1, 9:55 am, snipped-for-privacy@gmail.com wrote:

I have an insulation guy coming over in about 2 hours, what kind of questions should I be asking him (and what answers should I get) to make sure he'll do a good job?
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You can add more over it. What you add should not have a vapor barrier. In flat areas, you can just lay batts down over the old.
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how many inches though? If each inch is about 4 do I need to put about 8" over the 2" of wool I have now to get it up to code?
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..
dont block attic vents, and with a older home you likely need more ventilation too
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I can't answer code questions, but if you live in a cold or hot climate, more is better. Especially with the way energy prices are going. The 2" you have aren't going to amount to much when new stuff is on top of it, so I'd probably add whatever code requires or more, ignoring the insulation of what you have.
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