Honda Builds an Experimental House
The net-zero energy house at the University of California Davis incorporates many energy-efficient features and comes with its own battery-powered car
Honda's long list of consumer products already includes cars, outboard motors, portable generators, motorcycles, and lawnmowers — so why not houses?
The company in March opened the doors to the first Honda Smart Home, a high-tech, net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. house on the West Village campus of the University of California, Davis. It comes with many features that are becoming standard in high-performance houses — a ground-source heat pumpHome heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger. The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures., a roof-mounted photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. array for electricity, a gray water system for watering plants, and triple-paned windows. There's also a Fit electric car in the garage.
The 1,944-square-foot two-bedroom house is designed to produce all of the power it needs, including enough juice to keep the car charged.
Honda isn't planning on building replicas of the house elsewhere, or licensing others to do so, says Marcos Frommer, Honda's corporate affairs and communications manager. It's intended as a demonstration project only.
"It allows us to engage with the public and the technical community about a zero-carbon future while allowing us to research potential future solutions," Frommer said in an email. "Honda will be making available for free our architectural drawings and complete specifications so that others may conduct similar research, or build this house for their own personal use."
Honda didn't say how much the house cost to design and build. Construction started in April 2013 and the house opened on March 26.
Carbon reduction is a key part of the design
Together, homes and light-duty vehicles now contribute roughly 44% of total U.S. greenhouse gas emissions, Honda said, and developing technologies that help reduce that number is one of the project's main objectives.
In a detailed description of the house, Honda said it expected the house would generate a surplus of 2.6 megawatt-hours of electricity per year for a net offset of 6 1/2 tons of carbon dioxide. When the electric car is added to the equation, Honda said the total avoided emissions should rise to nearly 12 tons of C02.
Honda looked for carbon savings wherever it could find them, including the concrete used in the post-tensioned slab. Making cement from limestone by heating it up in giant kilns is responsible for about 5% of global C02 emissions, Honda said. So half the cement in this concrete was replaced with a concrete extender called pozzolan.
Energy management system can talk to the grid
The company developed a home energy management system that monitors and controls the generation and use of electricity. The electrical system, which includes a 10 kilowatt-hour battery in the garage, is designed to minimize the home's impact on the grid by responding to changing conditions. If the grid gets overloaded, for example, the system can reduce consumption in the house and route power from its PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. array to the grid.
The Honda Fit has been modified to accept DC current directly from the 9.5-kW solar array, which the company said is more efficient than converting the direct current to alternating current as would normally be the case. When making power at full capacity, the panels can charge the car's batteries in two hours.
Other features of the home include:
- Double stud wall construction. Above-grade exterior walls are made from two 2x4 stud walls on 24-in. centers designed to eliminate thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. except at the fire blocking. The 9 1/2-in. wall cavities are insulated with cellulose (R-31).
- Triple-glazed windows. The argonInert (chemically stable) gas, which, because of its low thermal conductivity, is often used as gas fill between the panes of energy-efficient windows. -filled casements are manufactured by Alpen.
- A truss roof with a vented roof deck. The roof is insulated to R-60 with cellulose.
- Insulated slab. Rigid foam under the concrete slab has an R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of 10.
- Airtightness. The house tested at 2.0 air changes per hour at a pressure difference of 50 pascals.
- Lumber. All lumber used in construction came from forests certified by the Forest Stewardship Council(FSC) Nonprofit organization that promotes forestry practices that are sustainable from environmental and social standpoints; FSC certification on a wood product is an indicator that the wood came from a well-managed forest..
- Water management. There are dual-flush toilets, and low-flow faucets at sinks and showers in the 2 1/2 baths. Outside, xeriscapingType of landscaping that requires little if any irrigation; suited to dry and drought-prone climates; generally relies on regionally adapted native plants. is irrigated exclusively with filtered gray water.
- Light system. LED lighting developed with researchers at the California Lighting Technology Center mimics the natural shift in daylight from morning until night. The company calls it "circadian color control logic."
Honda said it would seek certification from LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. , the National Green Building StandardNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. , and Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners..
Someone from the UC-Davis community will be living in the house; the name of the future occupant wasn't announced.