In talking with different builders some use Tyvek Wrapping for an additional layer of insulation and some full plyboard as opposed to the wrapping. Any thoughts on what is considered the "best" method when trying to keep your house insulated at this layer.

Any additional thoughts on Rfactor insulation for the walls and ceiling. Looking to make the best investment we can afford to make the house as efficient as possible. Thanks...

Tyvek is not an insulator, it stops air infiltration only. I'd use both. How thick is your wall cavity? If this is new construction try for at least 2x6 studs. Go with the thickest unfaced insulation that will fit and use a 6 mil poly vapor barrier on the inside.

That's the best answer, using both. In the 'old days' we also used to 'lay in or cut in' a diagonal 1x6 across a portion of each walls framing in order to absolutely guard against any of the walls coming out of square. Rarely seen these days, though.

I believe that "the best" would be using expanded polystyrene on the exterior sheeted walls (you can get it in 4X8 sheets from 1/2" to 2" thickness). Not only does the foam provide insulating value but it's a good vapor barrier also.

Kstar, I agree that poly gives the best insulation for the money but it does breath. It is moisture resistant but not moistrure proof. To get the best vapor barrier, especially over studs and small cavities where studs mate poly, still cover with a 6 mil vapor barrier. It is impossible to get a perfect seal around outlet boxes in the walls and up againist studs and headers.

Thanks for all the feedback. I'll talk with the builder and see what options I have.