GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Choosing Sheathing

eng251ine | Posted in General Questions on

I am in the beginning phases of a small addition to our early 1900’s home in zone 4a non-coastal Maryland.  With this addition, I am planning to add exterior insulation to the existing structure and new siding.   The existing interior walls are a mix of plaster and drywall, 2×4 dimensional studs (balloon frame), no insulation, 1×6 dutch lap siding, tar paper, fiber cement shingle siding.  What I am considering is removing and properly disposing of the existing siding shingles, adding blown in cellulose to the stud cavities, installing new exterior sheathing over the original wood dutch lap, a wrb,  adding 2” roxul comfortboard 80, ventilated rainscreen, Boral true exterior siding.  My questions are:
1. For sheathing options, would I get better or more preferable performance from plywood with taped seams and a wrb, or zip with taped seams?
2. If plywood with taped seams is best, should I consider a higher performance vapor open wrb like Deltavent or Blueskin or is this overkill?

Thanks in advance for your input

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member


    My own preference would be to go with plywood and a sheet WRB. It makes the flashing a lot more forgiving relying on laps and not tape.

    While I see the benefits of expensive interior variable-perm membranes, I'm not convinced the high performance WRBs add much that a good conventional one like Tyvek Commercial doesn't give you.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |