Attached to this post, you'll find the latest revision of our home plans (Revision #14). Things are starting to solidify at this point on the plans. Our land has finally thawed out & dried out enough that we hope to have our well dug in the next two weeks and may be able to work more on our driveway.
What isn't solidifying is our construction plans. So far, we've visited three straw bale builders and one conventional builder. The conventional builder, not surprisingly, has his doubts about straw and has heard of a couple of straw wall failures... we are trying to get more substantial information from his sources on where the failures have been. We want to be earth friendly and sustainable, but we don't want our house to fail! The good news is that we talked to the Fremont County building inspector and they won't have any problem with a straw bale home so long as code is met. He also added he had never seen one fail, which is quite reassuring. We're still 90% sure we're going with straw.
On the other side of the fence, the straw bale builders each have radically different techniques, making our decision quite difficult in which path to take.
One builder compresses the straw bales using a box beam combined with compression straps to eliminate air infiltration at the roof/wall junction. He uses natural clay-straw plasters, and spends lots of time shoving a thick gooey clay-straw mixture into all the gaps. It's a pretty ingenious system, but he also uses plenty of heavy timbers and foam insulation in the box beam, raising the cost of the home and requiring larger trees (less sustainable). He's currently building a straw bale home in Salida costing around $200/sq ft. He's also never built a home in Fremont County (where we will be building).
Another straw bale builder uses metal poles for structure and to reduce use of expensive timbers. Because of the strength of the poles, they can be placed ten feet apart, reducing thermal breaks... again an fairly ingenious system. He uses brute force to attempt to eliminate air infiltration at the roof/wall junction, spending up to a week cramming straw into all the nooks and crannys. He also uses a concrete stucco, which many in the straw bale industry claim is a faulty approach on two counts: (1) the walls don't breathe as well as they should and (2) that less permeable layer gives a place for water to collect if the temperature difference and humidity allow for water condensation. He says he has tested a home's bales a number of years later with moisture meters and found no problems. We also visited a B&B in Buena Vista with external cement stucco and it seems to be fine solution for their high exposed walls. On the otherhand, it's certainly not the most earth friendly approach. But the cost savings are substantial; he claims our cost can be as low as $110/sq ft. That's pretty amazing for these parts. When visiting one of his homes, it was of extremely high quality... His concrete floors were gorgeous. We definitely want to integrate that into many areas of the home. Overall, it was a beautiful home.
Neither of these builders have done blower door tests to check for air infiltration, which is somewhat troubling. These blower door tests are essential to ensure you have a tight house with few air leaks. We have no solid data on which technique is superior. In the end, I think we will choose a hybrid and see if we can subcontract out each of the builders for certain parts of the project. For example, we might have a concrete stucco exterior for durability, but we probably will have a natural clay-straw plaster interior. If moisture does collect on the inside of exterior stucco, it at least can dry to the inside.
We still have many more questions than answers at this point and we have a thousand decisions to make. The adventure continues...