Bathroom Wall Insulation & Vapor Barriers
Please help with this question/concern about vapor barrier for my exterior wall. I have linked my original thread that I have on the Remodel Forum. Typically I would have stopped there with the vapor barrier on the inside of my wall because of my geographical location. BUT I am concerned about causing a vapor sandwich because of the siding setup we have. Below is my last post on the Remodel Forum but I am not getting any responses. I have since read controversial articles on the topics. Such as this one that is at a site called Green Building Advisor that I found Friday:
Which side of the issue are your on ;)
Anyway, here is my latest post on the tread in the Remodeling Forum and the thread is also linked below.
Hello, I'm back ready to finalize what I am going to do with the exterior wall insulation of my south facing bathroom wall in Iowa. Central Iowa is zone 5 on the map above that Hollysprings posted. On another thread Worthy had a link to the building science site and I found another paper written that addresses vapor barriers. I linked it below.
I will have a shower and washer/dryer in this room. I will have a 170cfm Fantech exhaust fan in the room with remote fan in the attic and 2 vents, one at the shower and the other at the W/D stack.
EXTERIOR WALL DESCRIPTION:
2x4 stud wall that faces the south. There is one window in this wall. I will have drywall and latex paint on the interior finished wall.
The material that is on the exterior side of the studs is 1x8 T&G boards from the 20's when the house was built. Out side of the boards is an old siding of pressed composite material that is from the 70's. It looks like the original narrow wood siding was removed at that time. The last exterior layer was put on by Sears (over the 70's era siding) within the last 10 years. It is a vinyl siding with a 3/4 pink extruded polystyrene insulation under the vinyl. The polystyrene material is by Owens Corning and says "Weatherb...Exterior Protecti..." (I only have a small section of material to read).
I have been planning on using Roxul batt insulation. This requires a poly 6 mil vapor barrier sheet put on the inside surface of this wall. Then the stabled areas get covered with "Tuck Tape". Of course I can't find Tuck Tape in the US.
1) Will it be appropriate to put this vapor barrier on the interior surface of my studs with all the sheathing materials that are on the outside studs? Or will I be creating a vapor sandwich, causing damage to the studs?
2) Will Tyvek Tape substitue for Tuck Tape?
3) If not Tyvek Tape, what does substitute for Tuck Tape?
Here is a link that might be useful: HOW DO I PREP/INSULATE STUD WALL FOR MOISTURE PROTECTION AND INSULATION (BOTH EXTERIOR & INTERIOR)