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Exterior Insulation for Adobe Masonry Walls

jollygreenshortguy | Posted in Energy Efficiency and Durability on

Does anybody have experience with exterior insulation of adobe masonry walls? I know that materials such as spray foams are used. But I’m considering the possibility of applying 2-4″ of mineral wool insulation board to the exterior, lathing over it with vertical 1x4s to create a rain screen effect and then applying a 3-coat stucco over that. I can’t see any downsides, except that I haven’t heard it done before. (I know it’s done over wood framed walls.)

What are people doing these days to increase the energy efficiency of adobe masonry walls in new construction? Do any of you fellow readers have any favorite websites on the subject of adobe masonry homes?

And yes, I Googled every combination of search terms I can think of. All I find is the same material I was reading in the 1980s and early 90s. It’s still good material, but doesn’t answer a lot of the questions we face these days.

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  1. don_christensen | | #1

    I have been looking for the same information for a while, and you're right, much of what is available is old and largely anecdotal. Adobe isn't discussed much on GBA either. I found some resources you might find helpful:
    1) Joe Lstiburek has written quite a lot about continuous insulation on masonry buildings. BSI-079, Deep-Dish Retrofits, shows some construction details for insulating over structural brick and CMU walls with both rigid foam and mineral wool.
    2) Colorado Earth has a lot of data on their website in the Resources tab. They are a company in Golden, CO who manufacture and build with compressed earth blocks. There are white papers written by Emu Engineering and Energy Logic that discuss projects built recently in Colorado. The 'Performance of Earthen Structures' section has a lot of archived material from New Mexico on how to characterize adobe structures both with and without exterior insulation.
    3) features a slide show, 'Adobe House by the Rio Grande'. This builder fastened a 2 inch layer of EPS foam board to the outside, followed by metal lath and stucco. I believe this a common upgrade in that region.
    4) At the outer edge of DIY, there is a fellow in Silver City, NM who is building a traditional adobe home (website, visioncreationadobe). He is insulating the north wall with a framed straw-clay outer wall, covered with wire mesh and clay plaster. It's quite labor intensive, as the author admits.
    I live in Colorado, not far from the recent Marshall fire. Fire-resistant construction is on everyone's mind these days. If you go ahead with your project, I'd be interested to hear how it goes.

    1. jollygreenshortguy | | #2

      Thank you so much for your detailed reply. This is a really great resource.
      GBA is full of all kinds of good information but I do wish they would give a little more attention to approaches that rely a little more on natural materials, local resources, etc. It seems like the thrust is to turn every house into a petrochemical foam wrapped box.

  2. strongwater | | #3

    Antonio, where in the US are you? Curious if you ended up moving forward with your mineral wool + rain screen. I've been doing the same research for projects in Santa Fe, NM. So sad to watch these adobes go up and then get encapsulated in a few inches of spray foam or rigid petro boards

    Here in Santa Fe, where its so dry, we'll typically forego a true rain screen and simply do two sheets of paper to create an air gap, lathe and stucco over that.

    Some other options I've been eyeing, though many not on the market yet, and none too local:
    - Thermacork rigid sheets []
    They make an insulation and a cosmetic grade, and are now selling out of Austin TX via Cross Cabin []. You can leave it fully exposed, stucco/plaster over with an EIFS or with a rain screen style application like you mention.
    - HempWool is supposed to release a rigid board in next couple of years. This would be the geographically closest option using US-grown hemp.
    - Glavel [] out of VT is supposed to start producing foamed glass boards with renewably-powered furnaces, date TBD. Their aggregate is an option for inert sub-slab insulation too, but shipping is $$ and not ideal
    - Timber HP [] out of Maine is producing domestic wood fiber panels

    Have also considered spray applying hempcrete which lands at R2.5-3 per inch, but seems a bit silly to not just build the whole thing out of hempcrete at that point...

    1. jollygreenshortguy | | #4

      Hi! You've got some interesting resources there I'll be curious to explore. Thanks.
      I haven't been researching this for a specific project. I design "stock" house plans and would like to add a line of designs specifically for adobe/cob/rammed earth. Theoretically they could be built anywhere but the idea is to create something with a Southwest regional appeal.
      It's true, with stucco it's not really necessary to do the full rainscreen with wood frame construction. But I think the stiffness of the 1x4 furring would make a better base for the stucco lath, rather than trying to tie the lath all the way through the insulation. It's more for constructibility. The rainscreen gap is an added benefit.

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