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Membrane/details for open joint siding

tricks73 | Posted in Energy Efficiency and Durability on

New poster here. I’m Richard and getting ready to reskin a 60s ranch in lower Catskills with Hemlock we milled on site after a huge storm a couple of years ago brought a lot of trees down. I would like to upgrade the thermal envelope at the same time. Here’s existing/proposed wall assembly:
Existing
– Sheetrock
– 2×4 16″ OC framing filled with paperfaced fiberglass batts (thermal imaging and exploration in one area seems to indicate that it’s mostly intact)
– 5/8″ plywood sheathing
– Tar paper
– Fiberboard siding (to be removed)
– 1/2″ foil-faced EPS (to be removed)
– Vinyl siding (to be removed)
Proposed additions
– 2 layers 1-1/2″ Comfortboard 80 w/ staggered seams
– Delta Fassade S or Proclima Fronta Quattro membrane
– 1×3 spruce furring strips – painted black at open joints
– Hemlock siding w/ 1/2″ open joints stained on 4 sides w/ Auson Pine Tar Vitriol (https://www.auson.se/en/pine-tar-vitriol)

Any thoughts on this assembly from a thermal/moisture protection perspective? Feedback on using Fassade S vs Fronta or some other product to protect the Roxul/allow it to dry to outside and that will provide a black shadowline? A good mesh product to stop wasps etc nesting behind the siding? Painting furring strips on all 4 sides vs just at open joints?

Many thanks in advance for any guidance.

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Replies

  1. Steve Knapp CZ 3A Georgia | | #1

    I'll give your post a bump (and ask a couple of questions).

    Can you provide your climate zone? (See https://www.greenbuildingadvisor.com/article/climate-zone-map-including-canada).

    Is cost a factor? (Reclaimed rigid foam would be less expensive than rock wool.)

    Are you planning to tape the plywood sheathing?

  2. GBA Editor
    Brian Pontolilo | | #2

    Hi tricks73.

    For the most part I don't see any big concerns with your assembly. As Steve mentioned above, it's important to air seal, so consider taping the sheathing seams and using caulks and sealants as necessary to air seal where tape won't work.

    Also, is the WRB over the mineral wool intended to be your water control layer, or just a UV-resistant layer to hide the insulation from being seen through the gaps in the siding? In either case, you'll need to have a dedicated WRB to integrate with your windows, doors, and other penetrations, so it's important to plan that now. I assume that the felt paper will need replacement by the time you have siding and existing insulation removed.

    I don't have any experience or feedback on the two WRBs you are considering, but another option is Benjamin Obdyke's Invisiwrap, which is also intended for this purpose. BO makes high-quality products, so you may price out this as another option. And the open-cladding systems that I have seen don't seem to have much in the way of pest control. I'm sure that's because it is too obtrusive to the aesthetic, but I do wonder if a black mesh like BO's Cedar Breather would disappear behind in the gaps. Not sure...

  3. tricks73 | | #3

    Many thanks for your responses and suggestions.
    In response to Steve's questions:
    - Sorry for not providing the Climate Zone - it's 6
    - Budget is definitely a consideration, but I'm trying to avoid foam products where possible for a combination of reasons - thermal drift (XPS, polyiso), performance at low temperatures (polyiso), blowing agents (XPS), flammability / poisonous fumes when burning (all), chewability by critters (EPS)
    In response to Brian's questions:
    - Excellent points on the tar paper degradation and need for a dedicated WRB - since you both suggest taping the seams of the sheathing it sounds like we should remove the tar paper and use the WRB for dual-purpose - will look at the BO products and work on the window/door details

    Many thanks again

  4. Steve Knapp CZ 3A Georgia | | #4

    Richard,

    I mentioned reclaimed foam since it is widely available and costs a lot less than new insulation (foam or rock wool). Using reclaimed material actually is a fairly green strategy, but I understand your reservation about this material.

  5. Tinaraes | | #5

    Tricks73,
    We have a very similar project we are working on now with our existing rambler. Wondering what you ended up with and how it's working. Particularly wondering what kind of UV barrier you used. We are doing 3/4" open joint pine siding painted with pine tar over painted wood furring strips and rigid polyiso. Also, keeping our WRB at the sheathing behind the insulation so the black membrane is mainly for looks and bulk water.
    Thanks!
    Tina

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