[GSBN] Straw bale at high altitudes
Derek Stearns Roff
derek at unm.edu
Fri Jul 11 16:14:53 CDT 2014
It’s been a while since I was directly involved with an SB structure at such a LOW elevation, but I hear it is possible :-) Since you ask for anecdotal evidence, most of the projects that I have worked on or visited in New Mexico and Colorado have been at 5,000’ - 9,500’. The most recent International Straw Building Conference was held at over 8,000’, and in relation to that conference, we visited strawbale homes from a little above 10,000’ down to about 5,300’. In many ways, strawbale excels at higher altitudes, where temperature extremes increase the importance of high insulation levels. Most issues and concerns, such as snow depths, would be similar for all building methods.
While I don’t think the future owners will “have to build a full walk-out basement”, it is a common choice on sloped sites. In this case, regardless of building method, the first floor of the living space will have a framed floor. This floor can support the bales, without being drastically different from other building modalities.
Again, independent of building modality, the biggest concern in foundation design is likely to be seismic issues, which California pays more attention to than any other state, with reason.
On Jul 11, 2014, at 8:40 AM, Misha Rauchwerger <misha.rauchwerger at gmail.com<mailto:misha.rauchwerger at gmail.com>> 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,
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