Straw Bales & Solar Energy -- A Natural Partnership: Page 4 of 4


Inside this Article

Straw bale walls can be part of a whole-house plan to achieve high energy efficiency while keeping embodied energy low.
In a post-and-beam structure, bales are notched around the structural uprights, preventing thermal bridging. (See "Straw Bale Walls" sidebar.)
In an I-joist structure, bales are fit between the joists, which reduces thermal bridging compared to a conventionally framed structure. (See "Straw Bale Walls" sidebar.)
A bale wall will rest on a raised and insulated double sill.
Author and builder Rebecca Tasker (center) helps homeowners ceremonially set the first bale.
Exterior stucco can be lime-cement or, for reduced embodied energy, earthen-based, and any plaster used must be vapor-permeable.
Bale wall systems have fewer thermal bridges that cause heat flow across the assembly.
Well-sized roof overhangs protect the walls, and shade south-facing walls and windows from the intense summer sun. (See "Southern (Oregon) Comfort in a Solar Straw Bale Home" sidebar.)
A double airlock entry reduces air exchanges by stopping blow-through when the outer door is opened. (See "Southern (Oregon) Comfort in a Solar Straw Bale Home" sidebar.)
Clerestory windows let in natural light and admit solar heat during winter. (See "Southern (Oregon) Comfort in a Solar Straw Bale Home" sidebar.)
Thick walls make deep windowsills, for an old-world feel. (See "Southern (Oregon) Comfort in a Solar Straw Bale Home" sidebar.)
High ceilings paired with well-placed windows promote convective cooling. (See "Southern (Oregon) Comfort in a Solar Straw Bale Home" sidebar.)
A natural earthen floor covers R-15 insulation and provides thermal mass for storing passive solar gain. (See "Southern (Oregon) Comfort in a Solar Straw Bale Home" sidebar.)
Multiple layers of natural plaster, both interior and exterior, mitigate diurnal temperature swings inside the building.
Thick walls make for deep door and window openings. There are several structural and aesthetic ways to approach this.
Thick walls make for deep door and window openings. There are several structural and aesthetic ways to approach this.
The relatively simple, but labor-intensive, aspect of building with bales fosters community involvement with “bale raising” parties.

Appealing Building

Approaching sustainability requires longevity: we take care of things we love and the longer something lasts, the lower its environmental impact. Unloved buildings get knocked down; then there’s additional environmental cost to build new ones.

There’s no longevity without durability. Most conventional buildings are built to last 30 or 40 years. Compare this to straw bale structures built in the late 1890s that are still in use today.

Straw bale building owners care about their buildings because they’re charismatic. As soon as you start putting straw bales into a wall, people notice. People also notice a difference when they enter a straw bale home. Perhaps it’s the thick walls that offer a sense of security, or the hand-applied finishes that harken to a time when buildings were crafted, instead of manufactured.

Straw bale buildings invite participation. Because the materials are nontoxic, there is a tradition of getting friends and family involved in the process with work parties—days when volunteers come to help stack bales or plaster walls, not unlike an Amish barn raising. Work parties don’t make sense on every project, but can advance the construction process while engaging the community. Most people feel alienated from construction, and working on your own building is empowering: a foot in the door to further engagement. This leads to a feeling of commitment and stewardship for the building, which can lead to greater longevity.

Of course, straw bale is just the wall. For a truly healthy, high-performance building, attention must be paid to the rest of the building system, such as minimizing its overall size and its loads; incorporating renewable energy systems; selecting high-performance HVAC, electrical, and plumbing systems; and choosing nontoxic finishes throughout the building. With straw bale’s Appendix S added to the International Residential Code in 2015, and the California Straw Building Association’s (CASBA, Detail Book soon to be published, this form of building will receive the acceptance and recognition it deserves.

Web Extras

See a load-bearing shake-table test at

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