Bonus Room Floor Insulation Fix R19 vs R30

Old 05-29-12, 05:38 AM
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Bonus Room Floor Insulation Fix R19 vs R30

From what I have read, I have the typical bonus room setup for the Southeast. I'm in the Atlanta area. It is framed out with electric, and insulation batts are laying under the floorboards, down against the garage cieling gyp board. There is an air space of 2-4 inches between the kraft faced batts and the floorboards.

R-19 with facing (6.5") was used for most of the floor. Some areas only have R-13 (4.5"). The floor joists have a space of 9". I plan on using rigid foam boards to block airflow from the attic into the spaces between floorboards. So my question is this:

I have pulled out the R13 - not good enough. Should I pull out the R19 and replace with R30, which is spec'ed at 9.5" thick? The plan was to slide it under with pvc so that I don't have to pull up the floorboards. Will it be too hard to fit? And is it worth the trouble for the upgraded R value and to fill air spaces against my floorboards (somewhat)?

By the way I think I have the knee walls and rafters figured out. I have rafter vents, and I am furring out my knee walls to 2x6 to put a rigid foam backing on them before I add R19 in the knee walls and cathedral cieling. I'm going to get a ridge vent installed to keep the attic space cooler and work with my ridge vents. It was 125 degrees up there a couple days ago. I'll seal all rigid foam board backing with expanding foam sealant that comes in an aerosol can. I moved my air conditioning supply vents to the cieling near the far wall, and have added a large return to my system with my A/C contractor's advice.
Old 05-29-12, 02:27 PM
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Welcome to the forums! You didn't stipulate what size the joists were. If they are 2x10, the R30 will work fine. If not, then compressing the R30 will reduce the effectiveness of the insulation. What are "rafter vents"? I am sure you meant soffit vents. You are adding a ridge vent and that will complete your air circulation thingy. You will be able to tell a great difference once the air moves properly. Use minimally expanding foam to seal the boards, as the regular stuff will expand too much. Not a good value for the $ in your instance.

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