Hi all, just trying to get a little info regarding how to insulate a 14×14 porch -sunroom addition I am doing. I was thinking of spraying a inch of closed cell isulation to fill all voids in the 2×6 wall and 2×10 vaulted ceiling as well as the crawl space floor. Fill in the rest of the cavity with fiberglass bats. Then I was thinking of adding 3/4 inch polystryrene foam board to the outside of the walls. My questions are these (1) If I go with the closed cell spray and the polystryrene foam board should I have vapor concerns within the wall if I use unfaced batts? I live in eastern Colorado where typically we have very low humidity. (2) when installing the foam board do I bump out the window flange perimeter with 1x material the same thickness of the polystryene to even the wall before siding? (3) Lastly, If I go this direction, do I still need a house wrap? Thanks in advance. Dave. P.S. heat sources will be passive from the sun through a lot of glass onto stone-tile floor and suplemented with electric floor mat.
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What does "Fill in the rest of the cavity with fiberglass bats" mean? That would mean something in an answer to you. It initially sounded like, with all of the foam, there wouldn't be any remaing cavity. It would seem that you would want a conventional inside vapor barrier, then an outside membrane wouldn't be a problem.
What I mean is with one inch of sprayed foam there would be 4.5 inches left in a 2x6 wall cavity. This would be filled in with fiberglass unfaced bats. Then 3/4 inch foamboard on the outside of the sheathing. With this senario should I have any moisture concerns? It seems to me if I don't put a vapor barrier on the inside of the wall the wall should be able to breath.