Replies

1. Expert Member
   BILL WICHERS | May 09, 2022 08:36pm | #1

   It doesn't hurt to do both for some extra insurance. I would use polyiso though instead of XPS, which is a bit better for whole-year averaged R value, will be much easier to tape well (most tape doesn't like to stick to XPS), and will be greener too.

   Bill

1. 
   user-7653783 | May 10, 2022 09:04pm | #2

   Thanks for the reply. Could taping both lead to issues with trapping water? If I could only tape 1 which would be better?

2. Expert Member
   Akos | May 10, 2022 10:29pm | #3

   For a solid air barrier, you want to tape the sheathing. This generally gets you the best air sealing for the least amount of work.

   Make sure you seal up the sheathing to foundation transition as this is a big leak in most houses. Liquid applied sealant or a tape specifically rated for concrete is the best for this.

   If you can get at it, taping from the sheathing across your wall top plate and onto the ceiling drywall would seal next biggest leak spot.

   Once your sheathing is sealed up, taping the rest of the layers is optional. About the only thing I tape after the sheathing is any vertical seams in house wrap.

1. Expert Member
   MALCOLM TAYLOR | May 11, 2022 12:02am | #4

   Akos,

   I might be wrong, but I think this is a re-siding of an existing house, so the sheathing might have quite few holes in it. My preference would be a fully adhered WRB, if not that then a sealed regular WRB, and the foam as the option I'd least like to use.

   If this is a new build, then definitely the sheathing.

1. 
   user-7653783 | May 14, 2022 01:27pm | #5

   Thanks. Yes the sheathing is a mix of plywood and old boards so I don’t think taping the sheathing is an option because the boards are relatively narrow

3. 
   user-7653783 | May 17, 2022 09:24pm | #6

   I see this detail has the foam taped and no house wrap. Any thoughts on why?

   https://www.greenbuildingadvisor.com/app/uploads/sites/default/files/GBA_INDIVIDUAL_PDF_FILES/GBA_PDF_Series-2/2-00008.pdf

1. Expert Member
   MALCOLM TAYLOR | May 17, 2022 10:11pm | #7

   User ...783,

   They are using the foam as a WRB.