Re: Adding more attic insulation cost effective?

On Mon, 30 Jun 2008 10:51:52 -0500, me@xxxxxxxxxxx wrote:

My girlfriends home....abt 1800 sq feet in north
Missouri...... has 6- 8 inch fiberglass batting between
the rafters in the attic.

She was considering buying some more cellulose
insulation and blowing it in her self. Cost would be
abt oh say $400 tops I think.

BUT some questions!

1. Would adding insulation above 6-8 inches REALLY be
cost effective given the location and decent condition
of insulation already there?

We were both kind of surprised when looking around in
the attic to find that batting. We expected loose
insulation that had settled but this is not the case.

2. Can you MIX two kinds of insulation like that....
i.e. adding cellulose on TOP of fiberglass batting?


When my home was built 40 years ago, they installed R6 in the attic
which, presumably, met code at that time. Today, it stands at R60 and
that's the minimum I would consider adequate in our climate (7,800
HDD). If you're going to go through the effort and expense of
upgrading your insulation, you might as well kick it up a notch or two
higher given the direction energy prices are heading.

With respect to adding cellulose on top of fiberglass batting, I don't
think it's a good idea -- the extra weight would end up compressing
what you have in place now, reducing its effectiveness considerably.
I would be inclined to add R20 or, better yet, R40 fiberglass batts
perpendicular to the ceiling rafters.

Cheers,
Paul
.

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