rigid foam sheets doubled up?


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Old 04-03-06, 06:10 PM
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rigid foam sheets doubled up?

I want to insulate walls and ceiling of a northern Ontario cottage add-a-room, and wondered if I can use two or even three thicknesses (1-1/4" each-Styrofoam) for more R-value. Do they need to be glued tight together? Am prepared for a lot of cutting to fit 2x6 on 16" centres. Do foam sheets need a final vapour barrier?
 
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Old 04-03-06, 08:30 PM
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rigid foam sheets doubled up?

If you are lapping them you do not need an additional vapor barrier. Adhesive will be a plus from a construction standpoint and a tightness standpoint. By using adhesive, you do not have to worry about the stud spacing since you are installing a continuous thermal barrier over the wall. You will have a tighter wall than a typical wall with holes in the vapor barrier.

You will also have much less infiltration than a wall filled with fluff covered with pastic that is not aways impermeable.

You will get much more insulation for you money since you will not have the thermal short circuits (studs) that reduce the supposed Rvalue of fiberglass by 7 to 50%.

What you going to do with the floor?

Dick
 
 

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