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Old 04-11-2010, 01:48 AM   #1
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cellulose insulation life expectancy

Hi, it seems there are many experts in this forum. Maybe someone could shed some light for me.

I bought a 50-years old house and found blow-in cellulose insulation is used in attic. I do not know how long the insulation has been installed. What is the life expectancy of cellulose insulation? Can I add another layer of fiberglass insulation to the top of it?




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Old 04-11-2010, 09:59 AM   #2
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I'm not aware of any degradation of insulation
Compacting it will reduce it Rvalue, getting it wet may degrade it
You can put fiberglass over it

If there isn't a vapor barrier facing the heated house then use insulation without a vapor barrier
OR - if there isn't an existing vapor barrier:
Use insulation with a vapor barrier & put that under the cellulose - not as easy - more work


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Old 04-11-2010, 02:49 PM   #3
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without air sealing the attic floor no amount of fiberglass or cellulose will help much. Airflow from below due to stack effect will wash through these type of insulation freely. This wastes energy and causes ice dams. You need to fix all penetrations first. So move the insulation to one side.. air seal completely then place the insulation back. adding more is no problem but do not add any with a facing. (paper or foil) Adding more cellulose by renting a blower to spread is a far better approach. adding fiberglass does not do as good of a job. Be sure not to block off the eave soffit vents. Do more research on key points I make here or it will be wasted time on your part.
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Old 04-11-2010, 10:40 PM   #4
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Thanks, Scuba_Davis and Bob. These are good advices. I will keep in mind.
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