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?
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.
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!
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...
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?
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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