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Green Building News

And the Best Wall Is…

Christine Williamson discusses the "perfect wall" before moderating the debate and revealing the winner of this fun tournament of wall assemblies

Jess Chaloux

If you haven’t been following the Sweet Sixteen this year it’s probably because you thought basketball games were all cancelled due to the global pandemic. You’d be right about that, but you’d also be missing out on the fantastic educational opportunity afforded you by the architects, builders, designers, and tradesmen who submitted their wall sections for comparison in the #WallAssemblySweet16 competition on Instagram, and here on GBA.

Beginning in April, our BS* + Beer discussion group in Kansas City hosted a tournament of sixteen wall assemblies in head-to-head competition for the sake of fun and education. On April 28th Christine Williamson presented her thoughts on the “perfect wall” assembly and then moderated a discussion with finalists Mike Maines and Ben Bogie before awarding the championship belt to the winner. The discussion was fantastic and the results were surprising so grab a cold one, sit back and enjoy the Wall Assembly Sweet 16 Finale.

-Travis Brungardt is a partner at Catalyst Consctruction in Prairie Village, Kansas and a founder of the Kansas City BS* + Beer group.




  1. Steve Young | | #1

    Please give us an executive summary. i would need more than a 6 pack of cold ones to listen to 1 and 3/4 hours of this rambling presentation.
    I am sure there is good information in there but I don't have the patience for 1 and 3/4 hours.

    1. KauaiBound | | #8

      This was a mostly-great discussion. Lots to learn even though most climates don't need a super-insulated wall assembly.

      That said, think this contest went off the rails because no boundaries were set - and of course the most expensive assembly won.

      Think it desperately needed a more-nuanced contest - what's the most cost-effective wall based on most important criterias that Christine noted: 1) fenestration 2) air sealing and 3) thermal.

      1) Fenestration is mostly a matter of cost - but sure would be nice to get recommendations for cost-effective windows because most of us are only exposed to the few brands that can afford lots of advertising and paid influencers. There has to be some small window manufacturers offering outsized value.

      2) Air Sealing - this is where the most bang-for-the-buck savings are to be had, yet there's limited discussion on details/products other than those brands that do the most advertising and are pushed the most by paid influencers.

      3) Thermal - this contest seemingly focussed on thermal which is last in the heirarchy of importance and suffers from fast-diminishing returns. Do we really need very expensive super-insulated homes when it is increasingly cheaper to build less thermally-efficient homes and instead add more solar panels? On the social sites I visit (almost all builder-focussed), it's almost never discussed - because it's money out of their pockets to admit a less-insulated, easier-to-construct home with an extra solar panel or two is much cheaper/faster/less complicated (and may be given credit from an appraiser whereas extra insulation/efficiency is often ignored).

      What pisses me off the most is the lack of discussion about costs - it's a fantasy to discuss pros/cons without including costs.

      1. User avater
        Michael Maines | | #9

        If you followed the weeks-long discussions on @BS_and_Beer_KC's Instagram page, you would likely agree that the lack of any rules was part of the appeal--submissions were of every type and shape, and cost was discussed frequently, as was vapor movement, constructability and everything else you would consider when building a wall. My submission (probably not the most expensive submission, but among the more expensive ones for sure) was simply the best wall I've used; others entered assemblies that were cost-effective for their locations, and many of them made it past the first round. Even the final round was neck-and-neck between a relatively low-cost double stud wall (the submission was 12" but the same wall can be thinner/cheaper) and Ecocor's outrigger system that I submitted, which was nearly identical in many ways to Steve Baczek's submission which made it to the second round.

        The whole point of the contest was not to win, it was to educate and share ideas. That's why announcing the winner is relatively pointless--it's the content that was important. If you don't think the Ecocor wall makes sense, that's fine, don't use it. But if you followed along during the contest, or listened to Christine's overview of what makes a good wall, I would be shocked if you didn't learn anything. I know I learned several things and it also helped me think more about climates and markets where I don't work and thus don't have to consider.

        Anyone who is "pissed off" about this contest or the summary needs to reassess their priorities. The organizers in particular should be thanked for their efforts in putting this unique contest together--it was no small undertaking. And thanks to Christine Williamson for creating and presenting an overview, and moderating the discussion.

        1. Malcolm Taylor | | #10

          I enjoyed it. Funny how the restrictions on public gathering ended up making the discussion more wide-ranging and relevant to more regions. At least there are some upsides to all this disruption.

          I do think that the incredible recent proliferation of wall assemblies is a temporary thing. over time I suspect two or three in each climate zone will dominate, and the rest will rarely be used. That's probably a very good thing. Given the skills necessary to be a successful builder, including economic literacy, ability to manage workforce, subs, and consultants, get approvals, etc, it's unrealistic to expect them to evaluate a new custom assembly for all the factors Christine listed each time a client comes through the doors.

          An boy - you guys sure drink some strange things!

  2. Brad Mallory | | #2

    It is well worth the time, particularly the first 30 minutes or so.

  3. User avater
    Jon R | | #3

    tl;dr. I believe the winner is a cellulose filled double wall with Zip as the interior side air and vapor retarder.

    With 38 perms on the exterior and < 1 perm on the interior, I'd be interested in moisture measurements while AC is being used. 10 perms or less on the exterior may be wise in warmer climates. Or replace the Zip with plywood.

    1. User avater
      Michael Maines | | #4

      The two finalists were Ben Bogie's double stud wall with cellulose insulation and Ecocor's PassivWall, an outrigger system with a thick layer of cellulose on the exterior, which I submitted. Ecocor has done extensive modeling and is a Passive House certified opaque assembly. Both systems have several projects with data loggers to track real-world performance. They both work fine in heating-dominated climates but I don't know anyone who has used them in cooling-dominated climates. To find out who won, you'll have to watch the show.

      One note, when Zip gets damp it opens up to about 3 perms. Dry it's about 1.8 perms. (for 7/16" sheets.)

      1. Tyler Keniston | | #6

        Do you expect to see a large shift to exterior wood fiber insulation with Maine and regional builders if/when GO logic starts producing Maine-based rigid wood insulation?

        1. User avater
          Michael Maines | | #7

          Tyler, yes--especially if GO Lab can come in at a price that makes them competitive with rigid foam, as planned. I've talked with many high performance builders who will likely change to framed walls with exterior wood fiber, or at least offer it as an option.

    2. Rick Evans | | #5


      Your thoughts remind of a comment Katrin Klingenberg made on GBA a few years ago regarding a similar wall detail on her Smith House:

      "We teach people the recipe for superinsulated walls in all climates and tell them very clearly: don't replicate the Urbana wall in Louisiana - it'll fall apart."

      I also remember Thorsten Clupp talking about his Arctic Wall (very similar to Chris's and Katrin's wall) and how it works well in a dry, cold climate Fairbanks. He stated that he would never use that wall in a wet, humid place like Juneau.

      I believe Michael Maines when he says these walls have been tested and they work. But I disagree with Chris Corson that his walls would work anywhere "between the North Pole and the South Pole" :-)

  4. Donald Christensen | | #11

    I love Chris Corson's work, but...what's up with those stairs? No handrail in sight. Is that OK?

    RE: exterior wood fiberboard insulation - Would you protect that from insects the same as with rigid foam? Are the wood fiber products treated with something?

    I learned a lot from the presentation. Christine Williamson's tutorial at the beginning is worth watching twice.

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