Cellulose Over Loose Fill Fiberglass

 
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Old 02-28-2011, 12:58 PM   #1
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Cellulose Over Loose Fill Fiberglass


I am just getting into the industry and have looked at several attics that have 2-4 inches of loose fill fiberglass. After air-sealing and other prep work, is it advisable to blow cellulose over the existing insulation.
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Old 02-28-2011, 01:25 PM   #2
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Re: Cellulose Over Loose Fill Fiberglass


yes

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Old 02-28-2011, 01:47 PM   #3
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Re: Cellulose Over Loose Fill Fiberglass


Loose fill? You are fine with two caveats --- (as you mentioned) make sure you do the air-sealing work first (holes for wiring, plumbing, where the walls are, etc...) & no rodents or other critters have used it as an outhouse, home

As for batts - the answer is no
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Old 03-02-2011, 10:11 AM   #4
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Re: Cellulose Over Loose Fill Fiberglass


I would advise adding more loose-fill fiberglass rather than cellulose for several reasons. 1) Even though cellulose is a good insulator, because it is essentially ground up newspaper it has fire retardant chemicals added to it. Those chemicals can corrode wiring and will also be "washed" away over time as moisture collects on the insulation and then evaporates, leaving you with a fire hazard in the attic. 2) Cellulose is dusty and dirty compared to fiberglass and is much messier when its installed. You have to mist water as you install cellulose to keep the dust down...

Modern fiberglass is relatively user friendly, is guaranteed not to settle and has a lifetime manufacturers warranty...

Just my two cents.
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Old 03-02-2011, 10:17 AM   #5
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Re: Cellulose Over Loose Fill Fiberglass


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Originally Posted by millshome View Post
I would advise adding more loose-fill fiberglass rather than cellulose for several reasons. 1) Even though cellulose is a good insulator, because it is essentially ground up newspaper it has fire retardant chemicals added to it. Those chemicals can corrode wiring and will also be "washed" away over time as moisture collects on the insulation and then evaporates, leaving you with a fire hazard in the attic. 2) Cellulose is dusty and dirty compared to fiberglass and is much messier when its installed. You have to mist water as you install cellulose to keep the dust down...

Modern fiberglass is relatively user friendly, is guaranteed not to settle and has a lifetime manufacturers warranty...

Just my two cents.

Really? I would like to see your source for those statements. Corrosion of wiring and it becomes a fire hazard?

Before you cash the check for your 2 cents, you may want to consider the accuracy of what you post.
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Old 03-02-2011, 10:49 AM   #6
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Re: Cellulose Over Loose Fill Fiberglass


Here is a reference regarding the washing away of the fire retardant material. It doesn't specifically say "fire hazard" but it makes sense to me that if fire retardant chemicals are washed away from a flammable material, the result would be an increased risk of fire.
energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11660[/url*

We've heard numerous stories similar to this one regarding the corrosiveness of cellulose chemaxx.com/cellulose.html[/url]
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Old 03-02-2011, 12:50 PM   #7
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Re: Cellulose Over Loose Fill Fiberglass


My point exactly:

Manufacturers add chemicals to the cellulose to make it insect and fire resistant. The major disadvantage of cellulose is that it absorbs more water than fiberglass or mineral wool. This can become a problem if water leaks from the outdoors since cellulose wicks water into itself and stores it. Too much water can also wash away the fire retardant.


How much water is too much in an attic? The amount needed to "wash" the borate from cellulose would destroy the sheetrock and cause significant damage, yes?

Fiberglass is poor second as an insulation choice in construction, compared to cellulose...and independent studies, not from Owens Corning, confirm this.

I have yet to hear anything about corrosion caused by cellulose.
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Old 03-21-2011, 09:02 PM   #8
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Re: Cellulose Over Loose Fill Fiberglass


Quote:
Originally Posted by SLSTech View Post
Loose fill? You are fine with two caveats --- (as you mentioned) make sure you do the air-sealing work first (holes for wiring, plumbing, where the walls are, etc...) & no rodents or other critters have used it as an outhouse, home

As for batts - the answer is no



Why is the answer no for batts?
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Old 03-29-2011, 07:53 PM   #9
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Re: Cellulose Over Loose Fill Fiberglass


Blown cellulose or fiberglass are both good if done properly ( critters wont burrow in cellulose because of the boric acid) not that it matters. If the attic is properly vented there is no issue with either. If either gets wet from a leak they have to be replaced regardless.

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