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Rigid foil insulation: Bungalow installation- foil face to exterior or interior?

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  #1  
Old 10-16-11, 03:48 PM
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Rigid foil insulation: Bungalow installation- foil face to exterior or interior?

I am re-insulating my bungalow attic in Detroit, Michigan in order to make a bedroom in the space. I am planning on installing foil faced XPS (Polyshield) on furring strips between the 2X10 rafters (to create the ventilation channel) and then installing faced batt insulation below with gypsum board as the finish. The question is which way to install the XPS- foil face toward the interior or exterior? Additionally, is there any worry of moisture getting trapped and causing problems?
 
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  #2  
Old 10-16-11, 05:19 PM
airman.1994's Avatar
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Foil should go to outside. Saying that the foil is expensive I'd look for it with out the foil to save money.
 
  #3  
Old 10-18-11, 07:16 PM
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Location: canada
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Actually, here the foil is cheaper than the non-foil - not sure why, and the foil adds a slight increae in R value as it supposedly slows offgassing of the foam. I don't think there is any issue with condensation as the foil on the foam will never be perfectly sealed, allowing vapour to pass by. Even if it were perfectly sealed, I think the foam provides enough insulation that the foil facing inside will not be cold enough to form condensation. This of course means you should have a good vapour barrier on the warm side of the batts. They add foil faced on the outside of already insulated houses all the time, when residing to increase r-value in our climate which is even colder than yours and they even tape off the foil sealing it completely.
 
  #4  
Old 10-19-11, 10:13 AM
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Location: USA
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Polyshield is EPS, not XPS, and has a lower r-value/in than XPS. I don't think it is vapor permeable either. Why not use XPS? I think vapor impermeable foil may be problematic, but that's just me.
 
  #5  
Old 10-30-11, 09:06 AM
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Join Date: Oct 2011
Location: USA
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I want to insulate my house how much cost ? My house (200x200) feet. I know an insulate company like Isolierschlauch UL
Do any one know this site? is it reliably?
 
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