Building Straw Bale Panels

This post was written by Spring 2017 Intern, Rachel Fixsen.

A few weeks ago we went on a field trip to Fruita, Colorado, to visit Dave Swinger and check out his SSIP project. Dave Swinger (“Farmer Dave”) bales and delivers the straw we use for CR builds. SSIP stands for Straw bale Structural Insulated Panels.

Structural Insulated Panels (just SIP, one S) are widely used in conventional construction–they’re pre-fab building blocks usually made of OSB and foam that you can have delivered and erected on site to make complete walls. SSIPs, pioneered by natural builder Chris Magwood, are the same concept, but with straw and plaster instead of wood and foam.

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We enjoyed a scenic two-hour drive through red rock canyons, cloudy skies, and occasional sprinkles, to the rural outskirts of Fruita. Dave’s place is on a dirt road among green fields divided into small parcels. We passed flocks of sheep and slow-rolling tractors before clustering our cars in the gravel lot between three structures in the beginning stages of construction. One is designed to be a barn/tool shop, conventionally stick-framed and sheathed with OSB, with a concrete floor. The other two are intended to be homes. One is a conventional stick-frame house, and the other is an experiment in progress–it will be composed of straw bale insulated panels. Five or six panels had already been built and put in place on the poured concrete stem wall, and they had already stood out in the weather for about a year.

Dave wears a big cowboy hat, cowboy boots, and a long gray mustache. He welcomed us energetically and pointed out the straw bale outhouse before we gathered in the partially-roofed barn, sat on bales of straw, and talked about SSIPs. We had some guests with us–a CR board member with many years of conventional building expertise and former CR intern who is now in the natural building business in Colorado. Rikki and Emily, CR admin, were there too. Three kids and several dogs frolicked around as we talked.

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A stiff breeze blew gradually clearing clouds across the sky. We were alternately warmed by the sunshine and chilled by the overcast as Dave talked us through his trials and errors with the SSIP panels. The concept of panels is straightforward, but the devil is in the details. He had to design the frame so that it would hold square, devise a method of packing the bales that would ensure they were tight, figure out how to raise the extremely heavy panels (somewhere around 1500 lbs) once they were plastered, and contrive a way to keep the plaster from slumping once the panels were upright. Dave wasn’t satisfied with the panels that were in place, so he clawed into them with a hammer and treated us to an inside look at the plaster layers and packed straw inside. The weathered panels appeared to be in decent shape, but he pointed out where the plaster had slumped and how much of the aggregate was beginning to crumble off. He wanted to try some new ideas.

He and his assistant, Justin (a former CR intern), had prepared a couple of 4×8 forms for us to fill and plaster. We used his tips for packing the bales, trying one panel with the bales laid flat and the other with the bales on edge. We cut the strings of the bales so they would expand and fill the form tightly. Dave fired up the mixer and with around fifteen people working, we quickly laid down a slip coat and brown coat on each panel. It was definitely easier to plaster a horizontal surface than to plaster a vertical wall.

Seeing first-hand a job site with just a few people working on it really brought home the power of numbers. Aside from the build team, none of the CR interns have a deep background in building. We’re not experts, we’re just able bodies with willing minds. But directed by a few experienced leaders and guided by a schedule, we can build a house in a few months. Dave has access to materials and machinery, but with just himself and the help of a former CR intern, and occasionally volunteer hours from friends, his progress is much slower.

After we’d finished the brown coat, we talked about what SSIPs mean for the future of CR and the future of straw bale building. Emily wanted to know if we, the interns, thought the panels might be a faster and easier way to conduct future CR builds. We also discussed how panels would compare to stacking bales for the owner-builder, or how SSIPs in the mainstream market might affect the mainstream appeal of straw bale building.

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I’m conflicted about the idea of SSIPs in the mainstream, available “on the Home Depot shelf.” Part of the appeal of straw bale building, to me, is the DIY aspect, or rather, the do-it-with-a-big-group-of-your-neighbors-and-friends aspect. Another characteristic of natural building is the concept of local materials, and gaining a familiarity with those materials—where they come from, and how they’re processed. If you can buy a pre-fab building block, you lose that hands-on intimacy. SSIPs also open up the possibility of these natural materials being shipped long distances, eliminating the “local” part of natural building, and potentially significantly increasing the carbon footprint of these “low-impact” materials, especially considering their weight.

Before I joined CR, I didn’t realize there was a whole community and culture centered around natural building. That culture encompasses more than just construction materials and techniques. As a culture, natural builders care about the environment, they care about community, and they care about their personal health and their capability to understand and meet their own needs. Straw as a material has inherent properties that make it a viable building product—it’s light, it’s cheap, it can be conveniently formed and stacked, it has insulative value. SSIPs can bring those properties to the mainstream, but would the culture of natural building be compromised? Imagine you could order a set of SSIPs from a chain construction company and have them delivered and assembled on your site by an anonymous crew. Would other principles of natural building carry through? Would the home be designed efficiently, according to the needs of the occupants? Would it blend with its surroundings and use a minimum of toxic or environmentally detrimental materials?

On the other hand, even if no other tenets of the natural building culture were evident in this hypothetical home, at least the walls would be primarily made of non-toxic materials and be well-insulated. And maybe that is enough of an improvement on conventional construction to be worth the potential compromise. Like anything else, natural building will progress and evolve and branch and morph. It’s important to thoughtfully evaluate new methods and approaches but also to be open-minded.

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