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Need fiberglass insulation advice


k19_1234's Avatar
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Join Date: Aug 2009
Posts: 99
RI

12-10-09, 10:31 AM   #1  
Need fiberglass insulation advice

I ripped all the insulation out of my attic and need advice on what to install. The attic has 2x4 joists that are 23’ on center.

Home Depot has unfaced R30 insulation that covers 31 sq. ft. for only $9. Since it’s so darn cheap, I was going to buy as many rolls as I could. However, it seems that none of the major home improvement stores sell just vapor barriers/ Kraft paper (is there a difference between the two?). So I can’t lay the barrier down first and then pile on the unfaced R30 at $9 a roll.

Buying faced R30 insulation that only covers 50 sq. ft. is going to run about $40-50 a roll…which doesn’t compare in price to the unfaced R30 at $9.

Am I just out of luck? Do I need to buy the much more expensive faced insulation in order to get a vapor barrier?

(They do have faced R13 insulation for $10 a roll but it’s only 15 inches wide…which means I’d have to do a lot of cutting to get 23’ on center).

 
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Tolyn Ironhand's Avatar
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12-10-09, 11:21 AM   #2  
Is this a walk up attic that will be come living space? 2x4's are not enough for a live floor. If this is just the area between the rafters and joists or trusses then your vapor barrier should be next to the sheet rock of the heated living space. If this is just an attic I would use blown in insulation.

 
k19_1234's Avatar
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Join Date: Aug 2009
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RI

12-10-09, 12:36 PM   #3  
Posted By: Tolyn Ironhand Is this a walk up attic that will be come living space? 2x4's are not enough for a live floor. If this is just the area between the rafters and joists or trusses then your vapor barrier should be next to the sheet rock of the heated living space. If this is just an attic I would use blown in insulation.
Yes, it's the area between the rafters and trusses/ joists, however it has a pull down staircase. I doubt I'll be storing anything up there.

If I buy 15' wide insulation for 23' on center joists, is there any particular tape I should buy to seal the vapor barriers together? Will a polyethylene tape suffice?

 
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