blown in vs fiberglass


Old 03-15-07, 05:31 AM
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blown in vs fiberglass

Which is best for an attic?
However, I already have R19 Batts up there already and I was planning on addind another layer of R19 perpendicular. I've heard different stories on which one was better, just want to find out others opinions...
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Old 03-15-07, 01:15 PM
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I'd use rock wool batts like Roxul for the cross layer if you can find it. Personally, I feel that rock wool with the same 'R' value actually greatly outperforms f-g when the temps drop down to colder levels. I cannot substantiate this claim however other than to say that R values aren't calculated at low temps, they're done in heated labs.
Old 03-15-07, 02:37 PM
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blown in vs fiberglass

What type of a roof system?

For R19, I assume you have 6" batts or blown in. If you do not have 2x6 ceiling joists, you will have to blow in insulation. In this case, I would blow in cellulose.

If you have trusses or framed supports, blown in insulation will be best since it will completely cover and does not have to fit in 16 or 24" spacing.

If is is open with no obstructions, you could use batts.

Make sure you provide cardboard or foam "chutes" at the outer walls to provide ventilation.

Don't get too uptight about perfection, since your last layer is at the point of diminishing reyrns of insulation. There are better energy items to spend your time and money on.

Old 03-15-07, 07:37 PM
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Well it's an old house (built in 1895), has balloon framing and the roof is made of 2x6's, there is storage space up there but I don't use it.(not easily accessed). So the roof is actually just triangles made out of 2x6's. Later there was added support made of a 2x8 nailed down the center of the attic and 2x4's wedged between it and the center of one side of the roof slope.
Kind of unusual I think.
As for ventilation... I have no ridge or sofet vents, just an attic fan and two small screened in windows on each gable end.
Old 03-22-07, 10:08 PM
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If you have balloon framing, I wouldn't suggest fiberglass. The balloon framming is a great place for fire to go up to the next level. I would suggest putting up wood blockers, if you have access to the wall. If not, cellulose will be a much better choice than fiberglass. Fiberglass will melt in a fire and let it go to the next floor. Cellulose won't allow it.

The two screens on each end of the house is fine.
Old 03-22-07, 10:21 PM
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Blow in the cellulose it is much better to fill in any holes.n the other insulation that is there

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