blown insulation weight

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Old 08-05-02, 08:20 PM
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blown insulation weight

how much does blown insulation weigh. Is there some pounds per cubic foot or pound per inch. I want r40 in the attic but people are talking that it would be too much weight for the sheetrock ceiling. I would like blown because of all the pipes and ducts in the attic.
 
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Old 08-05-02, 08:54 PM
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Old 08-06-02, 05:27 AM
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The question was. How much does blown cell weigh in an r40 thickness, I need to know if sheetrock will hold it.
 
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Old 08-06-02, 12:02 PM
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As long as the sheet rock is 1/2 inch thick it will not play a factor. What really counts is how the sheet rock is attached. Depending on your area building code, usually the nails must be no more than 6 inches apart and screws 8 inches apart. But you should check with your local building inspector.

Cellulose can be installed differently. It will have a different weight if you just pour it in, blow it in with the setting set at a high air mixture (fluffing). or dense packing. In either case, if the sheet rock is attached properly, there is no concern with the weight of the cellulose causing a problem with the sheet rock. There are too many variables to estimate the weight per inch depth of cellulose.
 
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Old 08-07-02, 09:00 PM
rbisys
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Greetins,

FG generally weighs about 1/2 - 3/4 # per cu. f

If you have about 6" of FG there is little chance R40 will save you any heat and could increase your a/c bills because of the increased mass. On paper if figures out to a 7.5% increase efficiency. BUT, you have multiply that times the 20% you lose thru the ceil'g times your bill. On a 1500 sf house I believe it figures out to a 50 + year payback, if your lucky.

A better savings of about 30% in summer and about 15% in winter can be achived by installing a 2 layer, perforated radiant barrier over the existing FG. Would need to know what part of the country you live in and what amount of FG you have up there and what type of roof construction to give better info.

Thank you for considering my opinion.
 
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Old 08-08-02, 06:53 PM
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right now, new house, no insulation at all up there. House is 1/2 mile from gulf of mexico, mississippi coast. metal roof light grey painted. concrete block wall 100 % filled with concrete, double pane windows, r15 stud walls , eight feet covered porches east and west. No windows on north or south. House faces west. House is slab on grade.
 
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Old 08-09-02, 07:33 AM
rbisys
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Greetings,

There are 2 to 3 different ways you can do the radiant barrier (RB)insulation the RB would be your best choice since your load is from the ceiling. On layer of RB will out perform any amount of fiber glass you could put up there, plus, you won't have any moisture or mold problems. The material is stapled in with an air or commercial electric Stapler, 1/2" crown x 3/8 to 1/2 long

If it is a truess frame a 2 layyer would be very easy to install and cost you about $.25/sf x 500 sf rolls.

You might also want to check into radiant barrier paints for the walls. They are not as efficient as a pure oil (70% vs 95%) but could also help the comfort level.

Thank you for considering my opinion.
 
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