GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X 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

Hardie Board Prevail panels over exterior EPS board

PlusWoodDesign | Posted in Green Building Techniques on

I Live in dry and cold Alberta, Canada. I am planning to install Hardie Board Prevail boards  attached to 1×4 strapping over 4″ of EPS insulation . I will be using a Tyvec barrier on the sheathing below the EPS. The Hardie installation guide calls for a water-resist barrier on top of (on the outside of) the foam as well.  Why? Is this necessary? Surely it will serve to trap water vapour within the foam rather than release it? I would like to hear your thoughts on this. Thank You.

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


    There is no reason to use two WRBs. Where you put it, over or under the foam depends on how you want to integrate it with openings, etc. Both places work fine.

  2. Jon_R | | #2

    And even if you did use two, WRB is quite vapor permeable and so it wouldn't trap water vapor.

  3. PlusWoodDesign | | #3

    Thanks, Malcolm and John. I've read 'where-does-the-housewrap-go' and my windows will be 'outies' so I'll put the WRB on the outside of the 3" EPS foam board. Any recommendations for WRB?

    1. Expert Member
      MALCOLM TAYLOR | | #4


      I like Tyvek Commercial. It's a lot like regular Tyvek, but much harder to tear.

  4. PlusWoodDesign | | #5

    Thanks. I would think that putting WRB on top of EPS foam is not easy and because it is only sandwiched every vertical 16", easier to damage before the Hardie Board panels are applied; so, I appreciate the Tyvek Commercial advice. A peel and stick product may make application easier. Is there such a product that adhers to EPS foam board?

    1. Expert Member
      MALCOLM TAYLOR | | #6


      I've never used an adhered WRB. Looking at some of the manufacturer's installation video, two guys seem to have bit of trouble putting it on a mocked up wall in a shop. Maybe it's easier, or maybe it sticks to itself at every opportunity and is a nightmare.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |