Can I use polyiso over cellulose if I paint ceiling with low perm paint?
I thoroughly enjoyed Martin Holladay’s “Musings of an energy nerd” article regarding “Are Dew-Point Calculations Really Necessary?” from 9/17/2010.
There is a little confusion on my end in that the article seems to speak heavily on the wall portion of a house and not so much on the ceiling. Can I substitute ceiling for wall as I read the article?
Also, can you comment on my approach of insulating my attic?
Plan (from inside out):
Vapor Retardant paint ceiling with .4 Perm rating (Bin or Kills). The house is from 1962, so there may be enough oil based paint on the ceiling, but it will help me sleep at night.
Air sealing of all cracks and crevices, drill holes etc.
6” of cellulose between joists (newly sprayed in)
Two layers of 1.5” poly iso (unfaced). Seams staggered and taped.
One layer of Plywood
Christmas/holiday decorations on top
The house generally has a RH of 55%. On the high side – I know. I will utilize a dehumidifier if necessary.
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