Vapor Barriers in Bathroom

[MGBROWN]

I have just gutted my master bath and will be retiling my tub/shower surround. It is on an exterior wall so the alcove is surrounded by insulation, which I will be replacing with newer stuff. How do I handle the vapor barrier issue? I will be installing insulation with the attached vapor barrier. I plan to put up cement board above the bath tub and tile accordingly. The ceiling above the tub will have regular drywall put on it and a vent fan will be installed. Do I need to put a vapor barrier behind the cement board and have it overlap over the tub flange? What about the ceiling? If a barrier is needed what is the best type. What do I do with the rest of the exterior wall that is not in the tub, do I use Green board on it with a vapor barrier and what about the two interior walls are barriers need on these as well.
Any help would be appreciated.

[em69]

A vapour barrier is placed on the warm side between a heated and non-heated space. No VB is required between two heated rooms.

[MGBROWN]

If the insulation I am installing has the kraft faced paper is this sufficient on the shower wall i fI am using cement board?

[em69]

Kraft faced insulation may meet Code in your area, but it certainly doesn't in mine.
IMHO, Kraft faced insulation is not a very effective vapour barrier due to way it is installed.

[JPicasso]

Yes, use a VB behind the walls of the shower.
On the exterior wall, either use unfaced insulation batts, or
take a razor and put a handful of cuts through the kraft paper or plastic
that is on the insulation.
Overlap the tub flange, Yes.

No VB on ceiling.

I don't know about putting a fan IN the shower, but one installed in the
bathroom is a good idea. (I'm not saying it's a bad idea..... I don't know)

It's easyest to use 6mil plastic, so you can see through it and you can find
it in large rolls. For the rest of the bath, I'd use regular drywall, Greenboard
is falling out of fashion.

For the VB in the rest of the bath, I'd follow EM69's advice,
All I know about is puttin a shower together.

HTH

[MGBROWN]

Thank you all for your advice, I can now put the thing back together.