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Identifying the Water Control Layer in this Assembly

andyfrog | Posted in Energy Efficiency and Durability on

Is it the wood fiber board insulation?

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  1. Expert Member
    Malcolm Taylor | | #1


    The primary water control layer will be the cladding, The secondary layer, which I suspect will be behind rain-screen strapping, can be either a conventional WRB or the wood fibre insulation itself.

    1. andyfrog | | #2

      Interesting, thanks!

      Do you know why in the video linked below, they chose to use a fully adhered membrane on the Gutex?

      Isn't it a bit overkill?

      1. Jon R | | #3

        A fully adhered WRB can be a good exterior air barrier. And while it may be overkill for this, it is more resistant to water penetration.

        1. andyfrog | | #4

          Yes, the fully adhered WRB is a good air barrier--however, they specifically chose airtight sheathing as well (Finsa Superpan Vapourstop), which they also painstakingly taped. So I guess I'm a little confused when comparing it to Ben Bogie's assembly.

          1. Jon R | | #5

            Note that interior and exterior air barriers are not equivalent and there is benefit to having both.

            Ben's house apparently uses a mostly interior side barrier, which in a cool or cold climate is superior to the just the exterior side.

  2. Jon R | | #6

    If anyone is interested in more details about the roof:

    I think the walls and roof are innovative and well thought out. Less clear is if
    wood fiber board insulation is cost effective and the assemblies are IRC complaint. For example R806.1 requires "cross ventilation for each separate space". As I see it, the roof cellulose is in a space with no ventilation.

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