Insulation - Cellulose over Batts?


Our 40 year old home has a mixture of insulation in the attic. 2/3 of the attic has blown in cellulose, and the other 1/3 has fiberglass batt's that were added during renovation work.
Can I blow in additional cellulose over the whole area. If not, why?
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Kyle Boatright wrote:

yes you can blow cellulose over the fiberglass.
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marson wrote:

Marson may not agree but I think blow in sucks if you ever have to work up there again....
I like f/g batts / roll / blankets best.
cheers Bob
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No doubt about that, but what I really wanted to get at was whether there was any major downside to blown in over batts from the perspective of insulation value.
If there isn't, I plan to "top off" the settled cellulose between our rafters in the area where we store things, then reattach the decking on top of it. I figure that's probably 250 sf of the 1,000+ sf attic. I'll have another 8" or so of cellulose blown in elsewhere and may put down a couple of boards to facilitate walk paths for future maintenance before the new blown in material goes in.
KB

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Kyle Boatright wrote:

Over time, blown in cellulose insulation can/will settle down due to gravity ( reducing the air pockets between the cellulose ) and thus their insulating property will/can degrade over time. Fiberglass batts are more likely than blown in cellulose to maintain their insulating qualities over time. Installing fiberglass batts takes less skill to install and less equipment than blown-in cellulose thus making it a better DIY weekend project. ISTM - the current cost differential between blown in cellulose vs. fiberglass batts for most residential homes is not substantial enough to warrant it as a decisive factor. Fiberglass batts insulations are maintance free; blown in cellulose insulation will require that one add/redo cellulose insulation periodically to maintain its insulating properties.
I removed my attic blown in cellulose insulation (R20-R30) because it was settling down due to gravity and it was losing its insulating quality. I replaced it with new fiberglass batt insulation last fall (R38 - the highest R rating available locally and the thickest batt my attic could handle uniformly).
DOE has a new insulation standard for new construction now ( see page 6 and 7 in the U.S.DOE "Energy Saver$" booklet at http://www.eere.energy.gov/consumer/ or ask for the booklet by calling 1-877-EERE-INF, 1-877-337-3463). Older home may not have enough space along the edge of the attic to hold uniformly more than R-38 of fiberglass batts (12"-14" deep ceiling/attic cavities) so the higher U.S. DOE recommended R-rating attic insulation standards may not be viable -atleast using fiberglass batts. Stryofoam panels take up less space than fiberglass give the same insulating property so stryofoam panels could provide a higher level of insulation given the same space limitations in older homes. However, a stryofoam panels insulation project is going to cost significantly more.
HTH, Walter

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On 3 Dec 2006 10:50:50 -0800, walter snipped-for-privacy@my-deja.com wrote:

What method did you use to remove the cellulose? I had to be messy.
-- Oren
"My doctor says I have a malformed public-duty gland and a natural deficiency in moral fiber, and that I am therefore excused from saving Universes."
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Oren wrote:

My neighbot had blownin removed & f/g batts put in.....the crew vacuumed the stuff out! It was done in no time quick & easy
cheers Bob
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Kyle Boatright wrote:

No that is the only issue I know of. If I decide to add more, I will blow it in myself. I have both in there now. The blown in stuff tends to fill in small spaces and block air infiltration as well so you come out ahead on the insulation end.
--
Joseph Meehan

Dia \'s Muire duit
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