Insulation

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  #1  
Old 11-27-02, 12:24 PM
pcb
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Question Insulation

My garage's outside walls are 100% pegboard with no insulation in the airspace - I am planning on adding 3-1/2" fiberglass roll insulation with a paper backing. Which direction should the paper face? Is the paper ALWAYS supposed to face the inside of the house? Thanks.
 
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Old 11-27-02, 12:34 PM
R
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If you are inside the garage, the paper or foil should face you. You cannot install peg board over the insulation. Most building codes, if not all, state that insulation in a garage must be covered with a fire rated material, such as sheet rock. Then you can put the peg board.
 
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Old 11-27-02, 02:20 PM
rbisys
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Greetings,

Because of the thermal dynamics in a garage, FG can be a disaster. I have found that the condensation problem is sometimes worst in a garage than in the main house. Paper is not a vapor barrier if that is what you are after. The deteriorating paper, pitch and condensation can draw bugs.

If you can find some 4 mil reflective insulation (about $.20/sf), you will have far more insulation performance and none of the other problems.
 
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Old 12-04-02, 05:57 AM
pcb
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Originally posted by rbisys
Greetings,

Because of the thermal dynamics in a garage, FG can be a disaster. I have found that the condensation problem is sometimes worst in a garage than in the main house. Paper is not a vapor barrier if that is what you are after. The deteriorating paper, pitch and condensation can draw bugs.

If you can find some 4 mil reflective insulation (about $.20/sf), you will have far more insulation performance and none of the other problems.
Thanks for the reply. Follow up Q: What if I used unbacked FG and just covered it with the pegboard like it is now? Wouldn't that allow adequate ventilation to avoid moisture problems and avoid the fire hazard of the paper?
 
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Old 12-04-02, 10:04 AM
wingnut2
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pcb- I'd try to find foil backed FG or the reflective vapor barrier rbisys is referring to. If you can't find either, go with unfaced and a poly sheet vapor barrier.

You should always use a vapor barrier. Whenever you have a temp difference between the inside and outside, you'll need some sort of vapor barrier.
The vapor barrier should be installed on the warm side of the insulation (generally to the inside of the house).
 
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Old 12-04-02, 06:00 PM
rbisys
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Greetings,

The same pitch that is used on the paper is used on the foil backed. If you use the foil backed FG and want the value of the foil you have to have an airspace. But now, the foil is the primary insulator and the FG is useless. So just use the RB.

The vapor barrier does not prevent moisture from being pulled from the outside air source. Vapor barriers do not prevent condensation. Condensation causes up to 50% or more in increased heat flow, both ways, plus other related problems.

Thank you for considering my opinion.
 
  #7  
Old 12-05-02, 03:56 PM
T
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Vapor barriers

Vapor barriers are intended to stop indoor water vapor from passing through the drywall into the wall cavity and condensing on the inside of the sheathing. Vapor barriers always go on the warm side of the wall. These vapor barriers don't stop water vapor entering wall cavities from outside as rbisys indicated.

If you plan on finishing your garage, you need to check in with your local building inspector regarding permits, codes, and inspections.
 
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