Adding more attic insulation cost effective?

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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?
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On Jun 30, 11:51 am, snipped-for-privacy@privacy.net wrote:

It is not all that easy to say for certain, but I would believe it would be a good investment. Remember it will also make summer cooler or if A/C then it will be cheaper as well. I suspect that in the long run it would save on heating alone.
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Personally, I'd add more batts. If you ever have to do work up there, it will make everything far easier and cleaner. Just lift the batts out of the way, run your wires or whatever, and put it back. It is an easy job to DIY.
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I agree. Run the bats 90 degrees off the current bats and you'll close off a lot of the leakage.
I blew some cellulose into an attic recently that had blown fiberglass with some thin spots. It covers nice but is really messy if you ever need to get up there for anything.
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wrote:

When I added batts to the blown in in my attic, it took me maybe 3 hours to do the job.
I put them across the rafters as others have said.
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Confused
Do you mean to lay down more batts on TOP of current ones but at 90 degree angles to current ones...criss cross?
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On Tue, 01 Jul 2008 11:24:39 -0500, snipped-for-privacy@privacy.net wrote:

That's exactly what I did and that is the recommended procedure. A long pole will help the installation.
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OK
Thanks so much guys!!
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And a couple of illegals would make it even easier <G>
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snipped-for-privacy@privacy.net wrote:

Yep. The idea is to block any gaps that occur between the existing bats and the trusses/rafters.
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On Mon, 30 Jun 2008 10:51:52 -0500, snipped-for-privacy@privacy.net wrote:

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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So you would remove the old batts and install thicker bats in its place? That what you mean?
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On Mon, 30 Jun 2008 13:19:33 -0500, snipped-for-privacy@privacy.net wrote:

No, I would leave the existing batts in place and install the new batts on top, but run them perpendicular to the ceiling joists. This accomplishes two things: 1) it minimizes the weight placed on the existing batts, thereby minimizing their compression and subsequent loss of R-value and 2) it reduces the thermal bridging through the ceiling joists.
Cheers, Paul
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If the old batts come to the top or near the top of the boards, then place new batts at right angles to the old ones. This will cover up all the wood. In other words, if looking at the batts they go from left to right, place the new batts frount to back as you face them. Be sure if there are vents at the edge of the wall you do not cover them up. This is to ventilate the space in the summer and help with the cooling.
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snipped-for-privacy@privacy.net wrote:

If you're having this much trouble grasping the rather simple concept of ADDING insulation to your attic, you should hire a professional.
Go to Home Depot and look at an package of R38 insulation. Installation instructions are right there. The Pink Panther will show you how to install new insulation ON TOP of the old insulation, perpendicular to (90 degrees to, "criss-crossed", across the rafters, whatever) the existing insulation.
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On Mon, 30 Jun 2008 10:51:52 -0500, snipped-for-privacy@privacy.net wrote:

Depends on when she sells the house and moves. The breakoff point may be 3-10 years. I live in Tennessee and have 3 feet of insulation in the attic--helps the A/C. Don't forget about those Styrofoam or cardboard "chimneys" that are attached tot he roof to provide the proper ventilation and to help prevent ice dams.

Sure. Or you can add additional batts (without paper) on top of the existing ones.
A few infrared pictures of the house will tell you where the heat loss is happening. Caulking and/or replacing windows may be effective.
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How do you make an infrared picture of a house?
--
Jonathan Grobe Books
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  Click to see the full signature.
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wrote:

With an infrared camera?
What do I win?
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You have 3 ft of insulation in your attic!?
Is your duct work in the attic, and if so do you have it covered?
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????????????
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