Insulation, Radiant and Vapor Barriers - Attic Insulation Questions
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bhorn
01-02-07, 07:32 AM
I have some questions on how to insulate the ceiling and knee walls in an attic that we are finishing to usable space.
We are finishing our attac/3rd floor to give us about 600 additional sq ft. We are planning on installing kraft faced r30c fiberglass in the ceiling and kraft faced r15 in the 5' tall 2x4 knee walls.
1. Can we use 6 mil plastic sheeting over the kraft faced insulation in the ceiling and walls, or will this create 2 vapor barriors and cause problems?
2. There will be unfinished storage space behind the knee walls, can I install rigid foam insulation to the back of the knee walls to provide additional insulation or will this also create vapor barrior problems? Should I just use r19? I thought the rigid would give me less air peneration.
What is the best way to insulate this space? I'm concerned about the heat in the summer.
This area will have forced air HVAC and is located in central NC (where the summers can be hot) if that matters.
Thank you for all of your help.
Bill
We are finishing our attac/3rd floor to give us about 600 additional sq ft. We are planning on installing kraft faced r30c fiberglass in the ceiling and kraft faced r15 in the 5' tall 2x4 knee walls.
1. Can we use 6 mil plastic sheeting over the kraft faced insulation in the ceiling and walls, or will this create 2 vapor barriors and cause problems?
2. There will be unfinished storage space behind the knee walls, can I install rigid foam insulation to the back of the knee walls to provide additional insulation or will this also create vapor barrior problems? Should I just use r19? I thought the rigid would give me less air peneration.
What is the best way to insulate this space? I'm concerned about the heat in the summer.
This area will have forced air HVAC and is located in central NC (where the summers can be hot) if that matters.
Thank you for all of your help.
Bill