While most Americans recognize Honda as a transportation manufacturer producing cars, motorcycles, boats, and more, the company also has experimented with constructing homes, specifically smart, environmentally friendly ones.
Honda states the reason for the crossover is simple: They are “passionate about developing technology that solves our most pressing environmental challenges—a passion that extends beyond cars.”
Taking inspiration from a similar home project in the company’s operations in Japan, the Honda Smart Home in Davis, California, was built in 2014 to demonstrate a vision for zero-carbon living and mobility.
Unlike other concept homes, the goal of the project wasn’t just to build a sustainable home that features energy-efficient and green technologies, it was to study its effects on real inhabitants. From completion in 2014 to 2022, five sets of occupants lived in the home, generating crucial data from their stays and providing their honest feedback on what it was like to live in the green home.
“It was a great vehicle to talk about sustainability and also energy,” says Michael Koenig, Honda Smart Home project leader. “How do we get clean, renewable energy for your house and your transportation? Because then, it’s most of my footprint. How do we integrate those two in a way that the sum is greater than the individual pieces?”
What They Built
As a “living laboratory,” the home aimed to address water, waste, health, and materials, in addition to energy.
“We couldn’t just focus on the energy angle,” adds Koenig. “We really needed to think about the five pillars of sustainability, which is water, waste, energy, the health of the occupants, and the materials.”
With these objectives in mind, the two-story home’s energy planning started with a 9.5-kilowatt photovoltaic system mounted on the roof and Honda’s Home Energy Management System (HEMS).
As the home’s energy manager, the HEMS monitored all energy input, sent energy where it was needed, and kept the home comfortable. It also worked to improve grid reliability and could store direct current power in its battery for later use.
In addition to the home’s specific electrical loads, the HEMS also powered a Honda Fit EV, the car that was included with the project. When the solar panels were producing at full capacity, the vehicle could recharge in approximately two hours directly from sunlight, according to the company.
To reduce energy consumption from heating and cooling, the team leaned heavily on passive design techniques. The orientation, triple-pane windows, and overhangs were all optimized to help keep the home naturally cool in the summer and warm in the winter, while the thick, insulated walls and tight air sealing minimized thermal bridging and kept the conditioned air inside.
The team also utilized a geothermal heat pump. Opposed to drilling several hundred feet deep, the team experimented with helical tubing heat exchangers in eight boreholes roughly 20 feet tall. To complete the system, the ground heat was routed to a single pump for heating, cooling, and hot water, and distributed through hydronic tubes in the concrete floor and second-floor ceiling for radiant heating and cooling.
For the home’s materials, the Honda team paid special attention to the products it was selecting. From the low-carbon concrete floors to the recycled countertops, many have sustainable properties and will stand the test of time.
The team’s water conversation measures included a compact plumbing design, which relies on smaller pipes with shorter runs. By reducing the length and diameter of the plumbing lines, hot water arrives to the showers quicker and less water is wasted. Greywater irrigation saved 80,000-plus gallons of water as well, according to the team.
When it came to the health of the occupants, indoor air quality and lighting were important considerations. Walls were designed to not accumulate moisture, materials were selected to prevent off-gassing, and a mechanical ventilation strategy ensured clean, filtered air was provided. While thoughtful window placement fills the house with natural daylight, circadian-friendly LED lights with automatic controls also help residents stay comfortable at night.
What Worked Out
Once the smart home was constructed, it welcomed its residents. Over the course of seven years, the project housed families, friends, and co-workers. With their help, Koenig and his team were able to learn and adapt throughout the process and draw some of the following insightful conclusions based on their decisions:
- Net-zero energy was achieved, but the efficiency was lower than expected;
- Home power backup works, though weather dependency makes it uncertain;
- The radiant cooling design had long delays and a chilly slab underfoot;
- The integration of hot water and ventilation improves overall system efficiency;
- Compact plumbing saves water and improves hot water delivery;
- Some people prefer grass, but the xeriscaped plantings have thrived on greywater;
- Interior finishes remain attractive, and the low-carbon concrete slab is free of cracks; and
- Natural daylighting is always welcome, and quality lighting controlled in five settings improves comfort.
“The one key takeaway is that there is not one key takeaway. Sustainability requires hundreds of intentional decisions, and for some of these the book hasn’t yet been written,” concludes Koenig. “That was the real purpose of the Smart Home, to start conversations and to help move the ball down the field.”
Project Credits
Owner: Honda
Architect: LCRA Architects
Builder: Monley Cronin Construction
Interior Designer: MAK Design + Build
Controls: Cantara
MEP and Monitoring: Frontier Energy
University Partner: University of California, Davis
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