I’ve read a bunch on DP cels and also on icynene, trying to decide which to use to retro-insulate the bays in my old house. These are some of the things i’ve read:
* Do not use a vapor barrier, bec the cels are a big sponge and it’s easier somehow for the water to get in via little tears than it is to get out.
i Why is it easier for water to get in than out?
* Somewhere, somebody wrote that three coats of latex paint is the same as a layer of visqueen behind the drywall. OK, i get that it’s on the front side of the drywall, but isn’t the principle the same, that
i you’ve got a de facto ad hoc VB if you paint your walls?
* Then there’s the matter of felting the sheating boards, plus i had thought of putting up an aux layer of 1″ XPS on the exterior of my 3-1/2″ walls over this (can’t do on the interior side), but
i will the walls be breathing or asphixiating if i do that?