[GSBN] Straw bale at high altitudes

[Jacob Deva Racusin]

I can't speak much to elevation here in the northeastern US - we have 
just a smattering of peaks above 4K' - but I can say regarding high 
ambient humidity, abundant rainfall, extended periods of no sun, and 
pretty dramatic cold temperatures, we've had repeated and sustained 
success building with straw bale wall assemblies - provided the 
detailing is accurate to the climate!

We've built over Durisol blocks on quite a few projects.  Sometimes it 
works out great for the 14" blocks to line up with a 14" bale on edge 
(we've done this a few times to get the bales up off the slab/exterior 
grade for slab-on-grade situations).  Often, it's not that simple, and 
there is a floor diaphragm in between, or some other factor complicating 
the geometry.  This all depends on the type and location of the 
structural framing (structural bale wall v. interior post-and-beam v. 
exterior stud wall, for example), but probably the easiest solution is 
to frame a floor deck over the foundation walls, and build the bales 
atop the floor frame.  This allows you to easily provide blocking where 
necessary in the floor framing to provide structural continuity, and 
allows you to be much more flexible with the planes and thicknesses of 
your assembly components.  Other issues crop up, such as air-sealing and 
insulating the floor frame, and again ensuring there are clear and 
easily-defined load paths from the structural plane of the walls through 
the floor assembly onto the structural plane of the Durisol (which if 
memory serves is about 5-6" inboard of the exterior face, at the 
concrete core), but there are ways to mitigate all of these with some 
good design detailing.

Best of luck,
Jacob

On 7/11/14, 11:40 AM, Misha Rauchwerger wrote:
> I have a client that wants to build a straw bale house at 4000 feet in 
> the Sierra Foothills.  They have been getting conflicting information 
> about the wisdom of building with straw at that elevation.  In 
> particular there is the concern about the effects of moisture in the 
> wetter months, and possible condensation inside the walls.  They know 
> about the need for big eaves, and permeable plasters, but have been 
> swayed against the idea from a local green architect in town. Please 
> direct me to any research, or anecdotal evidence to support straw bale 
> construction under these conditions, or maybe there is valid concern.  
> I have only built in the lower/dryer elevations on flatter sites.
>
> They also share these concerns:
>
> Their lot is sloped, so they would likely have to build a full 
> walk-out basement on the lower level, and the living space on the 
> upper level.  This means that the full lower level is built of 
> concrete (probably Faswall or Durisol); will they would have to build 
> out the lower walls to match the width of the straw bales?  How is 
> this disparity in wall thicknesses usually resolved with the least 
> cost/impact?
>
> - With a walk-out basement, is it possible/reasonable to do a 
> stepped-foundation on the lower level to minimize the amount of 
> concrete used?  Or does the mixed use of concrete and post/beam and 
> straw bale construction create unreasonable headaches in the building 
> process?
>
> Thanks everyone for your comments,
> Misha Rauchwerger
> builtinbliss.com <http://builtinbliss.com>
>
>
>
>
>
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-- 
Jacob Deva Racusin
Co-Owner
New Frameworks Natural Design/Build

Author, The Natural Building Companion
Chelsea Green Press, 2012

(802) 782-7783
jacob at newframeworks.com
http://www.newframeworks.com
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