Attic floor moisture barrier

[IamTheWalrus]

In the latest issue of Fine Homebuilding, a "passive solar" house is discussed. How passive and how solar is a topic for a whole new thread, but I saw something in the details I wanted to question.

The bottoms of the trusses and ceiling joists were all first sheeted with 1/2" Advantech Zip panels, and the seams all taped with Huber's tape. This, before interior partition walls, all non-bearing, were framed.

Gypboard, taped, was screwed to the sheeted ceilings.

How effective might this be as a moisture barrier, and what might be the drawbacks of doing this in a winter climate?

[davenorthup]

Seems like a beefed up vapor barrier that is pretty standard here in AK.

6MM poly with Tremco behind it for air sealing.

Taped sheathing like that works even better until someone comes in a cuts a bunch of holes in it for recessed lighting... :)

In our winter climate - all vapor barriers are to the warm side.

[Martin Holladay]

I Am,
The traditional location for a vapor retarder is on the warm-in-winter side of an insulated wall assembly or an insulated ceiling -- so I'm not sure I understand your question.