Open Cell vrs. Closed, where to draw the line
Here in NC we generally spray 8″ to 12″ of open cell insulation, generally Demelec or Icenene, on the underside of our roof deck. I am constantly asked about closed cell vrs. open cell and what are the considerations that would make one or the other preferable.
Last year at the IBS I asked Joe Lstiburek this question and his response was that open cell was fine in the south where you have good drying potential and short winters but that north of New York it was better to use closed cell because open cell could take on moisture by diffusion and it could freeze within the structure of the foam and accumulate throughout an extended cold spell reducing the effectiveness of the insulation and leading to moisture problems in the spring when it dried out.
Joe’s word is good enough for me, but when I quote him to the skeptical masses they want more in the way of citations and footnotes than just “Joe sez so.” Does anybody have any such hard data about problems using open cell in areas with extended winters especially in roofs?
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