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Tyvek Thermawrap. Is there a need for a rainscreen?

JC72 | Posted in General Questions on

The Tyvek vs ZIP System war continues (YouTube is full of videos pitting one product against another).

I came across this Thermawrap (R5) product and wonder if anyone has used it and whether an additional rain screen gap would be needed?

I would only see this product being used in CZ3 or warmer.

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  1. Expert Member
    ARMANDO COBO | | #1

    You can download the installation instructions from the manufacturer. This product is good for masonry cladding with extra wide brick ledge to allow space for the 1.5" Thermawrap insulation, which it should not be compressed. You need to install 2x4 around openings to install windows and doors.
    To install board or panel siding with rainscreens (usually 1x4), we use rigid foam for continuous outsulation. In CZ3, you need 1/2" minimum, but mostly we use 1". To install stucco, we use StuccoWrap (or any 3D WRB) and Jumbotex 60 over the foam.

  2. NormanWB | | #2

    I have decided not to use the ZIP system due to concerns about the horizontal tape allowing water through the sheathing over time. I have also decided not to use ThermaWrap due to the extra cost, and the installation and compression issues. Instead I am using taped OSB, followed by Tyvek DrainWrap and taped foil faced polyiso, with an air/rain gap between the polyiso and the siding that also serves as a radiant barrier. I will be taping the vertical seams in the Tyvek, but may avoid horizontal taping because I am concerned that the wrinkly texture of the DrainWrap will cause a worse problem than what might happen with the horizontal taping of the Zip panels and that the tape would inhibit the free flow of moisture down the DrainWrap and out of the wall assembly.

    Interior sealing with Knauff Eco-Seal Plus, in addition to the taped OSB and polyiso should give me more than adequate air sealing.

    I am also in CZ3.


  3. GBA Editor
    Martin Holladay | | #3

    Tyvek Thermawrap R5.0 was reviewed on GBA. Here is a link to the review: Two New Exterior Insulation Products for Walls.

    The last time I checked, Tyvek recommends this product for only two types of siding: vinyl siding and brick veneer. Vinyl siding is inherently well draining, and doesn't require any additional rainscreen drainage gap. If you install Tyvek Thermawrap with brick veneer, you should follow Tyvek's installation instructions -- but I imagine that building codes still require a drainage gap between the brick veneer and the Thermawrap.

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