Jenna Yu was designing straw bale houses in California when a move back to Rhode Island inspired her to build an accessory dwelling unit (ADU) insulated with straw. This piece describes how and why she built with Ecococon straw panels.
This project is located in: Köppen–Geiger Zone Dfa, ICC Climate Zone 5a, in an area with 5326 Heating Degree Days and 1022 Cooling Degree Days.
Since straw bale building doesn’t have much of a presence in that state, Jenna wanted to build something for people to see what it was all about and to drum up design work. It’s a good fit for the Rhode Island climate, which has big temperature swings. According to Jenna, most of the houses in Rhode Island are heated with gas and oil and are under-insulated. If people had better building envelopes, minimized the energy input required to heat and cool their homes, and drew carbon out of the atmosphere by storing it in buildings, then Rhode Island could be better prepared for climate change. Using plant based building materials removes carbon out of the atmosphere and stores it in walls, creating one more effective strategy for surviving and thriving. In fact, the panels on this ADU store 26,172 lbs of carbon. Jenna chose to use straw panels for the walls for a few reasons: she’s a mom with limited time, there aren’t many builders in the area with straw bale building experience, the cost of plywood and other materials skyrocketed during the pandemic, and straw panel walls could help lower natural building labor costs of construction. Among the various straw panel makers she sent plans to, EcoCocon was the most affordable, fastest, and the only ones she found that were structural without a plywood or OSB layer around the exterior for structural shear strength. Others are making panels that require plywood wraps or other methods of structural support.
Peter Jensen, an EcoCocon representative in upstate New York, was very helpful in sourcing the panels. Jenna ordered the panels in April of 2022 and they arrived in late August of 2022. EcoCocon was fast and accurate. The panels arrived by boat from Europe and then by truck from the port, and just five people with a forklift were able to put up straw panels, roof trusses, roof sheathing, and loft framing and building wrap in six days. According to Jenna:
It was a very fun six days! I was surprised by how efficient and cost effective Ecococon panels were. I also was surprised at how beautiful the space looked when the panels went up. I’ve been on many straw bale job sites and the geometry of these structural panels were so pleasing! I was a little sad to start plastering over them because they looked so nice, but then of course the negative ions of the clay plaster kicked in and I was happy to get into the motions of DIY plastering.
Ecococon creates a 3D model showing panel type distribution so that panel buyers can fully understand where to install each specific panel. Each panel is labeled according to a letter code is as follows: P = standard panel, B = braced panel, S = sill, L = lintel, C = column, and I = inclined panel.
During panel installation they lifted the lower level panels by hand and used a fork lift to get the various higher up pieces of the building in place. Tight panel placement called for precision with the foundation, because the panels already came with very long structural screws that hold them securely to the wood base plates and to each other. The panels were 1″ too short in one area where the ADU connects with the existing house. The solution wasn’t too difficult; they chipped away at the existing house a little bit to manipulate two panels to fit. There were a few rain occurrences when they draped tarps over the walls to prevent soaking. Small amounts of moisture in the panels aren’t a problem. Prolonged amounts of a lot of moisture becomes an issue, as it would be for any wall system.
Interior earth plaster covers the interior partition walls made of wood lathe (left). Thanks to precise planning, the straw panels go together easily enough with a little help from a few bar clamps (right).
Once the insulated slab foundation and radiant heat floor system is in place, and baseboards installed with rockwool insulation between, panels can be unloaded and screwed together.
As far as Jenna can tell, there isn’t a natural building scene in Rhode Island. She learned about natural building young, growing up going to workshops put on by the California Straw Building Association (CASBA). Later on as an architecture student at the Rhode Island School of Design (RISD), her teachers had little interest in straw bale or clay as materials. She proposed a straw bale desert living structure in Joshua Tree for a thesis project and it did not land well with her advisor. Now she has the first straw home in Providence.
Jenna’s Advice to Those Considering a Project Like This: Work with the site, trees, light, sound, views, privacy, neighborhood aesthetics, and then make a list of your project goals and needs. I’d suggest you go as small as you possibly can with your design. Things always add up and cost more than you think. Also, check for lead paint if you’re adding on to an existing house. The ADU shares a wall with our existing 200 year old house. I didn’t think of this but its many layers include lead paint, so when we started scraping at our old house to join the two structures we churned up a bunch of lead dust.
Jenna Yu is a Bay Area born and raised Chinese American architectural designer with a passion for straw and clay as building materials. She’s been designing and permitting straw bale houses and buildings mostly in California, but also in Oregon, Massachusetts, and Rhode Island. She has worked with Skillful Means, BOA Constructor Design Build, ADU Collective, and collaborated with others designing fire rebuilds, additional dwelling units, tiny homes, homesteads, and studios. She was also the California Straw Building Association (CASBA) workshop coordinator and currently sits on the CASBA board of directors. She’s now building her own straw bale house in Providence, Rhode Island and works under the business name Jenna Yu Designs.
