Zero-Energy Homes for the Masses

Just five years ago, few people could have imagined that zero-energy homes (ZEHs) would be within reach of the average homebuyer by the end of the first decade of the 21st century.

But growing consumer awareness of green building benefits is rapidly increasing demand for sustainable features. Increased demand is generating green competition in the new-home marketplace, which is driving down costs and moving green construction to the next level.

This trend got a bump last year when California set zero energy (ZE) deadlines for new residential and commercial development of 2020 and 2030, respectively. This policy is expected to resonate nationally, as other states follow California’s lead.

As a result, both custom and production builders are beginning to offer new homes that produce as much energy as they use at price points comparable to those for traditionally built homes.

Zero-Energy Homes Affordability Now

KB Home is leading the charge to ZE in the single-family production home market, with KB Home Southern California introducing a 1,500-square-foot (139-sq-m) home ZEH prototype last fall in Lancaster, California, with a $200,000 price tag, or $125 per square foot ($1,343.75). This home not only produces all the electricity it uses, it also stores energy on batteries to sell back to the power company or use during outages.

KB Home was able to lower the cost for ZEH construction by forming strategic partnerships with the city of Lancaster, California, which waived fees and fast-tracked plan checks, and BYD Co. Ltd., a Chinese company that manufacturers lithium-ion batteries, solar panels, and electric cars. The partnership with BYD enables KB Home to buy batteries and solar panels direct from the manufacturer at a reduced cost.

While this home uses natural gas for kitchen appliances and to heat hot water, the owners’ overall energy bill will be little or nothing, notes Tom DiPrima, executive vice president, KB Home Southern California. He explains that the energy system not only produces 4 kilowatts (kWs) of electricity, it also pulls electricity off the grid at night at three cents per kW, stores it on batteries, and sells it back to Pacific Gas & Electric (PG&E) at the peak-hour rate of 22 cents. Since PG&E also is the region’s natural gas provider, electricity credits offset the cost for gas.

“The concept is how to make a home affordable not just by lowering the price, but also by cutting maintenance and utility costs,” emphasizes DiPrima. “We’re creating homes where you don’t have $400 to $500 more [on top of the mortgage] in back-end costs.”

To reduce the energy load by 61 percent, KB Home used a 14 Seasonal Energy Efficiency Ratio (SEER) air conditioner, LED lighting throughout with motion sensors to turn off the lights not in use, a radiant barrier that reflects heat on the roof, and rigid-foam stucco in walls to quadruple the insulation rating to R-19.

Water-conserving plumbing fixtures, along with drought-tolerant landscaping and a rainwater collection system for irrigation, also reduce the cost for home maintenance, cutting annual water consumption in half, from average usage of 1.2 acre-feet to .65 acre-feet.

Other sustainable features reduce occupants’ carbon footprint and provide a clean, healthy living environment, including use of nontoxic building products and smog-eating roof tiles that neutralize nitrogen oxide, the dangerous component in air pollution.

KB is building five homes in Lancaster and is planning two other projects in California, one with 13 lots in Riverside and another with 90 homesites in San Bernardino.

ZETA, a San Francisco–based design/build firm, is the ZE frontrunner in the multifamily market. The company works with developers to create ZE multifamily, mixed-use, and transit-oriented communities in urban infill locations throughout the Bay Area.

ZETA builds high-performance modular structures of up to five stories at its own production facility. “ZETA is using technology to drive down price and scale to a mass-market level,” says CEO Naomi Porat, noting that the cost for construction, excluding land and soft costs, is about $120 per square foot ($1,290 per sq m).

“The key message is you can get tremendous cost savings if the structure is factory built, because with savings in time, labor, and waste, higher-cost materials can be put into it,” Porat adds. “The expedited process cuts construction time by 50 percent, so there is incredible value when coupled with efficiencies of modular.”

Getting multifamily to ZE is more complicated than for single-family structures, notes Andrew Silverman, ZETA vice president for project development. “It’s not easy to do net zero as an option in multifamily. Everyone has to buy in to make it work,” he explains, noting that all photovoltaic (PV) arrays go into one inverter, but specific panels must be allocated to specific units. “That’s why it’s typically just done in common areas.”

In addition, building height and number of units are limited by roof capacity for solar panels, he says, pointing out that depending on size, each unit requires three to four panels. Therefore, only multifamily projects of three or fewer stories, such as townhouses and live/work units, are currently candidates for 100 percent ZE.

“Technology improvements could be the game changer for multifamily,” suggests Manny Gonzales, a senior partner in the Los Angeles office of KTGY Group, Inc., Architecture and Planning. “Technology is moving so fast, it will be easy to achieve California’s zero-energy mandates,” he contends, noting that development of new technologies and improvements in building performance and PV efficiency will reduce the number and size of solar panels required per unit.

The Process

There are many approaches to achieving ZE at affordable price points, based on the region’s climate, homesite, design, locally available resources, and other factors unique to a project. “Variances in regions affect siting, renewables, and other energy considerations,” notes Tim Shipley, co-owner of Pittsburgh-based SureGreen Construction, a custom builder specializing in sustainable homes.

He says that getting to NZ is a three-pronged process that includes the following: reducing the energy load, selection and design of a system to meet energy demand, and addition of renewables to produce energy.

The critical first step, according to experts interviewed by Urban Land online magazine is to create a high-performance structure. “There is a cost premium to get to zero energy, but you can get to 70 percent efficiency for little or nothing,” contends Shipley.

Don Ferrier, president/CEO of Fort Worth, Texas–based Ferrier Custom Homes, concurs. He uses a pyramid scheme to plan a ZE structure, with the base representing the focus on strategies that improve energy performance but cost nothing, mid-section materials and products that enhance performance, and top renewable energy systems.

Energy modeling programs like Rem/Rate, a U.S. Department of Energy/Energy Star–approved software by Architectural Energy Corp., help designers make energy-wise decisions by analyzing the impact of energy-efficiency strategies, design, programming, construction, and technologies on a home’s energy performance. Rem/Rate generates an energy profile of the home, along with analyses of each design change or improvement added.

Green by Design

“You have to start by designing the house with sustainability in mind,” stresses Austin architect Peter Pfeiffer, president of Barley & Pfeiffer Architects. “You can’t add green features on later. It has to be green by design and programmed intelligently before starting the design,” he says, noting that the idea is to do everything that doesn’t cost an extra penny before adding expensive technologies. Intelligent programming might involve creating space for the HVAC system in the middle of the house to reduce the length of ductwork and locating the water heater close to the point of need.

Home design varies by climate and site considerations. In a hot, sunny climate like Austin’s, the structure should be oriented to catch the prevailing breeze and shade windows in summer. An ideal floor plan locates areas with few or no windows, such as the garage and utility room, opposite living areas with lots of glass. This way, windows can be positioned for a southern or eastern exposure to limit heat gain, while non-windowed areas face west and north to block exposure to sunshine in the hottest part of the day.

“With urban and suburban sites, you’re stuck with what you’re dealt. But a good design can still get high performance,” Shipley notes. Pfieffer, for example, designed a home for compact sites at the city’s Mueller Airport Redevelopment project that maximizes potential to respond to solar and climate considerations. The design employs a passive thermal siphoning strategy to naturally cool and ventilate the home by placing a screened porch on the prevailing breeze side of the structure and stair tower on the opposite side. In addition, all sleeping areas are located upstairs to allow for energy-efficient zoning of HVAC systems, so sleeping and living areas are heated or cooled only when being used.

Enhancing Performance

“The challenge for net zero is how someone lives,” notes Jordan Goldman, engineering principal at ZeroEnergyDesign, a Boston-based architecture firm. “It takes commitment on [the] part of owners to turn off lights not in use and so forth, but investing in a structure’s envelope helps take the variance out of it.”

Certain building materials and products can increase energy efficiency and create a tight building envelope to decrease energy load, while adding little or no cost to the overall project. Structured insulated panels, for instance, improve energy efficiency and may cost more than traditional construction, but the added cost is offset by reduced labor costs and construction time, Shipley notes. In addition, a high-efficiency HVAC system with a SEER of 14 to 20 increases energy efficiency, while super insulation reduces energy load and may cut the size and cost for an HVAC system.

In sunny climates, using a light-color or unpainted metal roof or foil-backed radiant heat barrier to reflect heat maintains the attic temperature at about 85 degrees. In addition, high-efficiency, low-E windows block heat from sunlight, while letting in lots of natural light. On the other hand, double- or triple-pane windows insulate against heat loss in cold climates.

Topping the Pyramid

Competition and increased demand are driving down the cost of PV. Over the last year, the cost for solar panels dropped about 30 percent, according to DiPrima, who notes that 4 kWs—enough to power the average home—cost about $20,000, compared to $30,000 a year ago.

PV is the most popular renewable used in ZE construction, but cannot do the entire job in regions where sunshine is unreliable like the Pittsburgh area. Therefore, Shipley used a combination of PV and geothermal to get a 4,300-square-foot (400-sq-m) custom home located north of Pittsburgh to ZE.

The system includes 34, three-by-five-foot (1-by-1.5-m) solar panels, which produce up to 8,400 kilowatt-hours annually, and a state-of-the-art geothermal heat pump that absorbs heat from the earth and transfers it to the home. Adding a geothermal heat pump to the energy system adds between $10,000 and $30,000 to the cost for renewable energy because installation involves drilling holes in the ground 150 to 250 feet (45 to 76 m) deep.

Wind energy offers a renewable alternative under the right conditions. A wind turbine provides all the power required by a 1,051-square-foot (98-sq-m) cottage Ferrier built on a lake north of Fort Worth. Wind was chosen for the project because wind turbines already operating in the area had proven the product’s viability, he says. The lake offers Level 3- to 4-wind capacity, providing a constant southwesterly breeze of at least 12 miles (19 km) per hour. The 3.7-kilowatt WindStream system cost $18,600 installed and ready to go.

Sustainable builders also are beginning to offer ZE-ready homes—the whole package minus a renewable energy source. This allows new owners to take advantage of renewable energy tax credits and cash rebates offered by federal, state, and local governments. Depending on the location, renewable energy incentives can add up to significant savings on both equipment and installation. The city of Austin, for example, offers a generous cash rebate for installing a PV system of up to $50,000.

With the current state of the new-home market, it is difficult to predict if this trend might trigger a market comeback. Kirk A. Sykes, president of Urban Strategy at America Fund, a New Boston real estate fund, and vice chair of the ULI Council on Responsible Property Investment, says, “Right now, investors are just looking for the homeownership market to return—not so much a new product to sell, as just having buyers to sell to at profitable prices. That said, investors are interested in green projects, because all savings flow to the bottom line and green will increasingly enhance project returns on exit as it evolves to become the industry standard for all product types.”

He believes the residential multifamily market will return in the top ten U.S. cities over the next three to five years due to demand from 24- to 34-year-olds, the prime renter cohort. Noting that this group is concerned about monthly living expenses, he suggests that the trend to ZE may help recovery in sunny climates where PV works best, but probably less in the Northeast, where the payback period is longer and construction costs are higher.

“Hopefully, new ways of financing and reducing the cost of net-zero construction will be identified to encourage this important new approach to energy consumption,” Sykes concludes.