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unique foam insulation situation- a new twist to this discussion

unique foam insulation situation- a new twist to this discussion


  #1  
Old 08-16-12, 02:38 PM
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unique foam insulation situation- a new twist to this discussion

i have one inch of sprayed close cell on the inside surface of my roof sheathing- its all 2x12 rafters and cathedral ceilings (hot roofs). I was going to spray celluose to fill remainder of rafter cavities but have an opportunity to use (cheap) 2 1/2 in rigid iso foil faced foam, which is also a vapor barrior.

Question- would it be ok to use several layers of the rigid instead of the cellose spray in. Keep in mind that because the closed cell spray is an irregular surface there would be an air gap between it and the rigid foam.
 
  #2  
Old 08-17-12, 07:51 PM
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Zone 4; http://resourcecenter.pnl.gov/cocoon...s/full/973.jpg

Table 3; http://www.buildingscience.com/docum...d-roof-systems

No cellulose without air above it in a cathedral; BSI-043: Don't Be Dense
Canned foam the layer next to drywall.


Gary
 
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Old 08-18-12, 03:59 PM
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When you use another insulation type with CCSF, the CCSF needs to make up at least 50% of the R-value. If it doesn't, you run the risk of water vapor condensing on the spray foam after it makes its way through the other insulation.
 
 

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