location houston texas
24 x 62′ motorhome garage add on attached to existing 1950s ranch style house
Garage: 2 x 6 studs with 1/2 plywood sheathing, conditioned attic.
hardie lap siding over 1 x 4 vert screeds , then 2 to 3″ foil ISO two layers if 3″.
Would a drain plain be called for between the foil and WRB, foil would be taped (any tape that would streatch when foam shrinks ??)
WRB either vap open or vap closed ???? I have yet to find good info on this choice
Inside of the plywood will probably be 4″ OC SPF or 1″CC SPF and rock wool bats or cellulose
My big issue is with a peal and stick that is vapor closed, what happens with any water that gets behind the foam. what would be the most practical drain plain.
Or should I ditch the drain plain and go with a vapor open peal and stick
what would be the best tape for the foam, foil tape is great but has no give if foam shrinks. Can 3m all weather flashing or siga wigluv $$$ handle any movement of the foam
would the above flash and bat option be too vapor closed to allow drying should the ply get wet
the garage will have AC and Heat and a fresh air source (50 cfm continuous or greater when needed)
any help would be greatly appreciated
with the V open P&S and the 1" CC SPF on the inside might be pushing it (foil ISO on one side even with a drain plain and 1" CC on the other side -- double VB )
Is there anyone out there that can help me with this decision.
I would suggest you try looking into a local source for more accurate information. I know that Houston has some crazy heat and humidity concerns. The way you insulate will probably be a bit different from a lot of people on the forum as their climates (including mine) are a bit different. I see extreme winter and summer. Winter here tends to create more moisture problems in the wall than summer. In general, you only want one vapor barrier in a wall b/c you will trap moisture between multiple vapor barriers. Also, foam itself when installed at proper thickness is usually considered a vapor barrier, so no other vapor barrier would be required. Again refer to local folks or guys on this forum from the area to help. Insulation has become a very complex issue these days, it’s not a straightforward process. Sorry, not a lot of experience in your area. I know mold is a serious issue in Houston, so will not attempt to tell you what is best.
now if I can just get some knowledgeable locals in my area to respond.