Installing straw bale insulation

Straw bale insulation requires a lot of collaboration and physical labor, and on Saturday, September 30, through the capable hands of the architects of the project—David Arkin and Anni Tilt, plus their team and 23 FRLT volunteers, the project was completed in record time! 

The Sierra Valley Preserve Nature Center will host an array of public programs, a series of permanent exhibits and interpretive experiences. The facilities will be a beautiful example of sustainable design techniques including solar power, water conservation and recycling, waste reduction, and straw bale insulation!  

Putting in the Work

There’s a job for everyone at a bale-raising. Full bales can be stacked horizontally in a brick-style staggered approach in the wall frame. In places where the bales need to be a smaller size or maneuvered around a post, the bales need to be split by hand to fit into the allotted spaces. 

Several stations were set up around the building for splitting bales—a technique that requires two people to thread the compacted straw with bale needles and retie the two sections before cutting the original bale twine. Other jobs include sweeping leftover straw from the ground and stuffing the excess straw into the gaps in the wall.  

Once a row is complete, bale twine is used to secure the bales to the studs of the wall framing with a nail gun. Then the process begins again for the next row. 

Now that the bales are all installed and secured, the next step is to seal everything in with two layers of plaster.

Interested in natural building techniques? Join in on the plaster work party to complete the walls of the Nature Center the weekend of Oct. 21–22. Learn more and register here: Plaster Workshop in Sierra Valley.

The Science behind the Technique

The new Nature Center features straw bale insulated walls using the hybrid Straw-Cel method. With plywood and cellulose insulation between the studs on the exterior face, straw bales are stacked inboard of the wall for an R Value of 43 (indicates thermal performance), which is excellent for the harsh winters of Sierra Valley.  

This process is a standard for Arkin Tilt Architects, the designers behind the new Nature Center. See more of their work in sustainable design and construction at their website. 

The straw bales for the Nature Center were sourced from The Nature Conservancy’s Staten Island Farm in the Sacramento-San Joaquin River Delta. The project to create the Sierra Valley Preserve Nature Center and all of the facilities and programs at the Preserve is a collaborative initiative of Feather River Land Trust, the Northern Sierra Partnership, and the Nature Conservancy. 

Read more about the plans for the Nature Center here.