Low Carbon Farmworker Housing Prototype at Blue Dot Farm

2024 Residential Design Awards Merit Recipient

Low Carbon Farmworker Housing Prototype at Blue Dot Farm

Blue Dot Farm is a sustainable business dedicated to equity – both for the environment and the farm workers who tend the land. In replacing farmworker housing, they wanted to developed a flexible prototype that is sustainable, efficient, and comfortable, addressing the acute lack of adequate rural housing for the people growing our food and fiber. Designed for agricultural communities, it is made with agricultural materials: primarily straw and sheep’s wool, salvaged wood siding and trim, and remnant earth masonry units.

The farm worker housing prototype is a simple, efficient building that balances privacy and community with private bedrooms, each with its own entrance and balanced light, as well a variety of common spaces, including a well daylit main room and a substantial porch. Structural exterior walls and clustered plumbing provide flexibility for interior partitions to fit the needs of different farms.

Simple passive solar strategies and a well-insulated, fire-resistant envelope create an a resilient, energy-efficient structure. The unique hybrid strawbale wall system is easy to build, leveraging standard stick frame construction. Carbon-sequestering straw bales are infilled between 2×4 framing with plywood sheathing, allowing for a range of low-cost exterior finishes, and producing an R-30 wall assembly. This removes a perceived barrier of building with bales, helping people put an affordable, locally grown, carbon-storing insulation to use, addressing both the climate and housing crises – achieving 40% carbon savings for its size, and 80% from a typical house.

Plan sets are available for free, and efforts are underway to garner pre-approval in other jurisdictions.

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A comprehensive and beautiful approach to a prototype that addresses a significant need in California: compact livable shared dwellings for farm workers. The jury appreciated the understanding of the vernacular of farm worker housing and how the prototype brought it into the 21st century with thoughtful sustainability features.

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Measure 1: Design for Integration

The project integrates low embodied carbon and passive performance to create resilient farmworker housing. It achieved a substantial reduction in embodied carbon by using biogenic carbon storing materials: strawbale and cork insulation, straw fiber board paneling; as well as low carbon emitting materials: low carbon concrete, earth masonry units, sheep’s wool insulation, and wool carpet. It features a unique hybrid strawbale wall system to provide the benefits of strawbale construction (carbon storage, U-value, acoustic separation) in an affordable, builder friendly design.

Passive survivability and fire resistance are key in rural environments. The generous porch blocks summer sun while providing outdoor living space. The tall common space allows heat to stratify, and vent out of clerestory windows which also provide daylight – this dormer can be oriented on either side of the main room, adapting to the specific siting. Lime plastered strawbale walls bookend the building, providing thermal mass to absorb heat from the day and release it at night. Each bedroom also includes openings on two sides for cross ventilation. This results in only requiring a single small electric heat pump to provide additional heat in the cold months, keeping energy bills to a minimum.

Measure 2: Design for Equitable Communities

There is a severe shortage of safe farmworker housing in California. Farmworkers are a vulnerable population who often endure overcrowded, moldy, damaged housing conditions. As a state we need to prioritize the protection of farmworkers. As a profession we need to provide solutions to the dual challenge of this housing shortage and climate crisis. This farmworker housing unit design takes on these challenges and provides a flexible prototype for other farm owners and make it easier for them to invest in housing the people who do the work to keep us all sustained.

Measure 3: Design for Ecosystems

By replacing a moldy mobile home for farmworkers, this project improves the health of people who tend the land with regenerative agriculture.
The new house is sited further from the forest, which along with fire resistant assemblies, reduces the risk of a structure fire.
It is built with plant and animal by-products. The carbon sequestering straw is from organic rice farms in the Delta. The sheep’s wool insulation is from low grades of wool that are not fit for clothing. With no foam and minimal synthetic materials, it will not pollute the ecosystem at the end of life.

Measure 4: Design for Water

The farmworker house includes a greywater to sub-surface landscape irrigation system. This will keep the surrounding landscape watered as a buffer against wildfires all year round, avoiding using precious potable water. The rainwater to irrigation system will be used by residents to water garden beds for personal use. The adjacent garden shed and greenhouse includes a rainwater storage cistern used for irrigating crops.

Measure 5: Design for Economy

The construction cost is estimated at $450,000. (The prototype was built in Marin County for $750,000. In addition to the high cost of construction in Marin, there were a number of finish upgrades by request of the farm’s owner including processing salvaged redwood, lime plaster, and cor-ten roofing, and site infrastructure improvements).
Integral to achieving the low-cost / low-carbon goal of the project is the Bales on End Between Studs wall system. This allows builders to conventionally frame with 2×4 studs, with straw bales inserted afterwards. Plywood sheathing provides cost effective lateral structure and flexibility for any exterior finish.

Measure 6: Design for Energy

By prioritizing passive heating, cooling, and ventilation, a well-insulated envelope (with a conditioned crawlspace), and thermal mass, the building only requires a small electric heat pump for space heating. The building is all-electric and sources electricity from a 100% renewable energy provider. The prototype site is in the shadow of a forested hill, so the roof is not a viable option for solar PV.
The prototype is designed for adaptation to different sites. The dormer can face the front porch or the rear depending on site orientation and climate, and the porch roof would be very suitable for photovoltaics.

Measure 7: Design for Well-Being

Materials for the project were carefully selected to be non-toxic, natural materials – such as straw bale and sheep’s wool insulation – for a biophilic sensory experience both during construction and in the finished space.
Material safety data sheets were analyzed for no Red List materials and no added formaldehyde. A reverse osmosis water filter is included. Each bedroom features a short hallway for privacy, as well as operable windows and an exterior door for balanced light, cross ventilation, and direct access to the outdoors. The common room is washed in daylight and well ventilated thanks to the operable clerestory windows.

Measure 8: Design for Resources

The project achieved a 40% reduction in embodied carbon per floor area (using BEAM Estimator, LCA phases A1-A3). With half the area of the average new home in the US, it represents an 80% decrease. It uses carbon sequestering biogenic materials (strawbale and cork insulation, straw fiber board paneling) and low carbon emitting materials: 40% reduced cement concrete, locally made earth masonry unit stem walls, sheep’s wool insulation). The project utilized local salvaged materials for their environmental and aesthetic benefits: framing and redwood siding from the former farmworker housing, trim from old barrels, interior doors from local salvage stores.

Measure 9: Design for Change

This is housing that enables the transition to a regenerative agriculture.
Structural exterior walls and clustered plumbing allows for a variety of interior layouts (from bunk rooms to a single family) to fit the needs of different occupants over time.
Facing intensifying wildfires, extreme heat, and power outages, this project is designed for passive survivability with a well-tuned passive solar design and natural ventilation. Fire resistant elements include: a metal roof, a metal skirt around the deck, conditioned crawlspace, perforated steel exterior shutters, lime plaster exterior finish (lime plaster applied directly over bale is a 2 hour rated assembly)

Measure 10: Design for Discovery

A post occupancy evaluation and occupant satisfaction survey are in the works. The feedback from these will inform revisions to the next iteration of the project. An operations manual has been compiled with instructions on how to operate and maintain the mechanical equipment, water filtration, and greywater system as well as optimizing the building for passive performance. A booklet has been published that provides an overview of the project to interested parties. This is available, along with the plan set, for free to anyone interested in building farmworker housing. We will learn from and amplify others’ iterations on this prototype