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gonjah[_3_]

On 5/17/2014 5:48 PM, wrote:
On Sat, 17 May 2014 12:02:44 -0500, gonjah wrote:

On 5/17/2014 11:04 AM, Tony Hwang wrote:
trader_4 wrote:
On Saturday, May 17, 2014 11:13:59 AM UTC-4, wrote:
On Fri, 16 May 2014 22:26:53 -0700, "Bob F"

wrote:

wrote:

Hi,

My attic has 2x6 joists. The (ancient) fiberglass insulation between

the joists appears to be matted down to about 2" thick.

Do I rip it out and replace with 6" thick batts and add more above

that?

Or do I leave it, add 4" batts, and add more above that?

All opinions appreciated.

I have no idea where you are, but up north, thay are using a lot
more than 6"

these days. I filled the joist space, then did another thick layer
over that

(R30??).

He DID say he was going to add more above.

I missed that. I guess enough insulation to fill it up
to the level of the top of the joists, then loose cellulose
gives the best energy solution. I wonder what the energy difference
is if you use just thick batts? There would be some gaps
between them, ie between joists, which would cut down the
performance. Topping it with blown-in would be better from
that standpoint. Only thing about blown-in I don't like is
that if you have to do some work, eg find an electric, phone,
CATV etc cable, it's going to be a pain in the ass. But I
guess you don't have to do that very often.

Matted down insulation has poor insulation value. I'd remove the old

first - and be tempted to have a spray insulation applied (about 2

inches) to act also as a vapour barrier and then fill with blown

insulation above that.

Sounds like unnecessary complication to me. I agree if it's matted,
it has low R value, but so what? It's still greater than zero, and
if you put what you intend to put on top of it, you have the new plus
whatever is existing. A little more insulation and you avoid the
work and disposal, etc of ripping the old stuff out.

Hi,
My question is how come it matted down? Moisture problem one time or
another? I want to make sure about this. Is there vapor barrier under
neath?
If all is good, I'd just add more insulation by any means. Here it is
R60 in the attic.

If it's like my attic it's dust piled up over the decades. I think, when
I finally get the funds together, I'm going to have old insulation left
in place with cellulose blown over it. With vaulted ceiling it's
probably the best solution. Back in '83, when they built my house, they
used some kind of rock wool insulation. Seems to work okay, but I'm sure
it's not anywhere near present standards.
Roxul is still about the best insulation you can buy - it does not
absorb water, it does not support mold, or mice.

That's nice to know. I have vaulted ceiling in well over 50% of my house
and access to some areas of the attic requires a contortionist.