Jay Yoo

OMG Jim, this is such a detailed answer to basically all the questions that I had in the last month. Thank you so so so much for taking the time to address my questions and even more. I have not thought about over-massing would be a problem. I normally do not build with such massive wall either!

I totally, wholeheartedly agree that this double wall system is redundant, over-massed, complicated, expensive, labor-intensive, quite incompatible, and still carbon-heavy. But the client is really excited about the idea of using three different materials, straw, wood, and concrete/earth, especially the permanent/durable nature of concrete/rock. He must have taken the story of Three Little Piggies a little too seriously.

We are currently looking for a way to print earth instead, but most projects that 3-d print earth seem experimental and funded for research rather than this private project.

I really appreciate the research and resources you recommended. These are fascinating! especially the Japanese example. Your suggestion of using fibrous rain-screen matting is very appealing. It can minimize the air gap that can introduce moisture but also separates condensation from strawbales.

Another much debated topic is the use of earthen render or lime plastering of the strawbales. The owner was apprehensive about plastering the bales' exterior because...
1. the Client will DIY a lot in this build, and does not want to prepare and apply plaster. He is more inclined to use mechanical/dry fastening systems.
2. Could be cheaper/easier/faster to apply a housewrap to achieve air-tightness and waterproofness.

So, the properties that are missing in tyvek, but present in plaster is that 1. fire retardant. 2. Pest Prevention
Is it absolutely necessary to include plastering because of these two reasons?

We are currently in the process of running environmental simulations to see what would be the best course of action.

Thank you again for your time, and your advice cleared a lot of things up for us.
Best,
Jay Yoo

Hi Erik, Thank you for the reply and advice.

Yes, complete water isolation is why there is a waterproof but vapor-permeable house wrap on the outside of the bale wall, and then a rain screen to further protect the wall. Also, 2.5ft overhangs on all sides.

My concern is that, if I go this route, I will be creating a rather airtight wall assembly. Then I assume I can't promote dry-air circulation within the wall? is this correct? or is the convection created by heat from sunlight or of the summer promoting air circulation within the wall, even though the wall is airtight? (The wall will still be vapor permeable on both sides, even though it is not the highest permeability)

The reason behind the 3-d printed wall is that my client is extremely interested in it and it is a new experience for us to build with 3-d printing technology.

Wow, thank you for the reply! I will swap out the vapor barrier with a permeable one. I would love to try building with structural strawbale, but this project has always been about 3-d printed house, not a strawbale house, the strawbale part is my minimal effort to make this project slightly more sustainable and to use locally sourced materials
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Hello awesome people!! I recently joined the forum to research and ask you experts about insulating a concrete wall with strawbale. Please be kind and hear me out if my plans will work.

Because most 3-d printed concrete walls are insulated by injecting closed-cell spray foam in between the 3-d printed cavities of a wall, when the building reaches the end of its lifecycle, there is no possible way of recycling the concrete for other uses, not to dismiss the use of petrol derived spray foam in the first place. So, I at least wanted to make the insulation part of this project sustainable.

I understand that in standard strawbale wall cases where wooden framing or structural bale walls are used, it is best to use vaper permeable finishings on either side of the wall.

However, as I am stacking the strawbales on the outside of a 3-d printed concrete wall (which has a mortar consistency/grain size for printing) (I also heard from the 3-d printer people that the concrete they use is vapor permeable, not sure to what degree), and because we live in a somewhat colder climate, northern New York state, I am worried about vapor intrusion and it condensing inside the strawbale during winter times when we don't have much sunshine to dry it off.

Are my worries totally unfounded? Is it best not to use a vapor barrier in cold climates for whatever construction type? What if the concrete cracks and introduces a massive amount of moist air inside the bale wall during our almost 6-month-long winter? Wouldn't it be a smart idea to prevent a failure that is destined to happen?

As of now, my wall design consists of, from interior to exterior,

""concrete wall - vapor retarder/barrier - 2x2 furring strip for air gap - 18" strawbale - clay plaster or vapor permeable house wrap - rain screen finish""

I tried to deal with the condensation that might happen on the surface of the vapor barrier during the humid summertime by creating an air gap between the barrier and the bales.

Will this system work? Or is it a better idea to replace the vapor barrier with a vapor-permeable membrane? like the one that will be used on the exterior of the bales? and get rid of the airgap because now even though the condensation happens, it can dry out to the interior. (although I am not too confident in concrete being able to dry that moisture out...?)

I will attach a drawing of the wall section here also, please give me some advice on how I should treat the bottom of the wall where it meets the foundation.


I really appreciate the help!!!